Published on February 21, 2014
Industrial biotechnology 1. Introduction During last 20 to 30 years the field that is developed so fast is genetic engineering. Genetic engineering uses rDNA technology to produce products related to health and medical but that was in the early days. In 1980 it was the first time the term industrial biotechnology was used 1.1. Definitions 1. Industrial biotech can be defined as the study of large scale profit making production of living organisms and their products for direct use or input for the manufacturing of other products. For e.g: we use yeast for animal feed for bread making and it is also used for making alcohols and wine which are used further to produce medical and pharmaceutical products 2. Industrial biotech uses biological systems for the production of chemicals, materials & for the production of energy. Biological system includes enzymes for the completion of any particular process we can also use the entire microorganism 3. Industrial biotech is the multidisciplinary field like we must have the knowledge of microbiology, mathematics, genetics, molecular biology, biochemistry etc and the major purpose for having the knowledge of different fields is that we should be able to produce commercial products using natural resources which mainly include microorganisms. 1.2. CHARACTERISTICS OF MICROBES 1. Highly versatile. 2. They can be grown on natural and renewable resources. 3. Have high reaction rate. 4. Have quick growth. 5. Can be easily genetically modified. 1.3. Industrial biotech is also known as white biotech because it have got positive environmental aspects like: 1. Reduce waste generation. 2. Reduce energy consumption 3. Remove use of solvents 4. Elimination of dangerous intermediate products 1
Before industrial biotech chemical industry was used to produce commercial products. Industrial biotech uses renewable resources like wheat, corn, straw etc Chemical industry uses fossil resources like coal gas and petrol etc 1.4. Advantages of industrial biotech over chemical industrial: 1. High reaction rate. 2. Improved conversional efficiency. 3. High product purity. 4. Low energy consumption 5. Decrease in chemical waste. And because of these advantages the industrial biotech is starting penetrate the chemical industry according to recent statistics the use of industrial biotech in chemical industry was 5% which was increased in the year 2010 to up to 10%. Green chemistry is a field that is used to treat industrial waste so industrial biotech is also a contributor of green chemistry. 1.5. History of Industrial biotech: Traditional fermentation process such as those involved in the production of dairy products and alcoholic beverages have been performed for thousands of years. However it was less than 150 years ago that scientific basis of these process were examined. The birth of industrial microbiology largely began with the studies of Pasteur, in 1857 he finally demonstrated that alcoholic fermentation in beer and wine production was the result of microbial activity rather than being a chemical process. Pasteur also noticed that certain microorganisms can spoil beer and wine and that some fermentation aerobic and others were anaerobic. He went on to device the process of fermentation which was originally developed to preserve wine. 2
Hansen: Of further advances that were followed non were more important then the development of pure culture technique by Hansen at Carlsberg brewery in Denmark. Pure strain brewing was carried out here for the first time in 1883 using the yeast isolated by Hansen referred to as Saccharomyces Carlsbergenesis, which is now classified as a strain of saccharomyces cerevisiae. Acetone Butanol fermentation: Around the turn of 20th century there had been major advancement in the large scale treatment of sewage, enabling significant improvement in urban communities. However, the first novel industrial scale process to be introduced was 3
the acetone butanol fermentation developed by Weizmann in 1913 using bacterium clostridium acetobutylicum. In 1920s industrial fermentation process was introduced for the manufacturing of citric acid. Citric acid industrial fermentation process In 1940s antibiotic penicillin was produced by further innovations in fermentation. And not only did production rapidly move from small scale culture to large scale submerged fermentation but it led to great advances in both media and microbial strain development. 4
Most recent progress includes the ability to produce monoclonal antibodies for analytical, diagnostic, therapeutic and purification purposes pioneered by Milstein and kholer in the early 1970s. Many of the greatest advances have followed the massive developments in genetic engineering (recombinant D N A technology) over the last 20 years. In recombinant D N A technology we have the donor organism from which the gene is transferred to the host organism by using a specific vector. Host can be prokaryotic E. coli for example or eukaryotic for example yeast, a vast range of important products many of which were formerly manufactured by chemical processes are now most economically produced by microbial fermentation and biotransformation processes. Conclusion: 1. The birth of industrial microbiology began with the studies of Pasteur in 1857 who finally demonstrated that fermentation was carried out by microbial activity. 2. Pure culture was developed by Hansen in 1883. 5
3. First novel industrial scale fermentation process to be introduced was acetone butanol fermentation by Weizmann in 1913 using bacterium clostridium acetobutylicum. 4. In 1920s industrial fermentation process of citric acid was introduce, in 1940s penicillin was developed. 5. Over the last 20 years greatest advances have followed the massive developments in genetic engineering. 6
2. Typical Fermentation Process A typical fermentation process consists of: 1. Fermentation raw materials. 2. Production microorganisms. 3. From which Fermentation is started. These three things include in the upstream processing And then we have two more things that are included in the downstream processing 1. Product Purification 2. And product formation. 2.1. Production Microorganism: The objectives behind production microorganism include: 1. Initially obtaining a suitable industrial microorganism 2. Strain improvement to enhance productivity and yield. 3. Maintenance of strain purity. 4. And continuing development of selected strains to improve the economic efficiency of the process. 2.2. Microbial products include: 1. Primary metabolites 2. And secondary metabolites. Primary metabolites are essential for the growth and reproduction of microorganisms and it include amino acids, organic acids, vitamins and industrial 7
solvents and they are produced during active growth in the leg phase or trophophase of microbial reproduction. Secondary metabolites are not essential for growth and reproduction and mainly include alkaloids and antibiotics they are produced in the idiophase or stationery phase of a batch culture after biomass production has peaked. 2.3. Fermentation Medium: Then we have the fermentation medium composed of raw materials containing essential nutrients. In many instances the industrial media is product from other industrial processes notably sugar processing, lignocelluloses wastes etc. 8
Fermentation: Fermentation is performed in large fermenters often with capacities of several thousands liters. The fermenters and the associated pipe work etc must be constructed of materials usually stainless steel that can be repeatedly sterilized and that will not react adversely with microorganism or with large target products. Fermentation Products: Can be broadly divided into two categories 1. High volume low value products like food stuff. 2. Low volume high value products like fine chemicals and pharmaceuticals. Food beverages, food additives and supplements: High volume low value products continue to be major fermentation products world wide and are of vast economic importance fermentation dairy products for example result from the activities of lactic acid bacteria in milk which modify flavor and texture and increase long term product stability. 9
Yeasts are exploited in the production of alcoholic beverages notably wine and beer. Also most of the amino acids and vitamins used as supplements in human food and animal feed are produced most economically by microorganisms. In addition, some microorganisms contain high level of proteins with good nutritional characteristics suitable for both human and animal consumption. This so called single cell protein can be produced from a wide range of microorganisms cultivated on low cost carbon sources. Industrial Chemicals and fuel: It includes low volume high value products. Fossil fuel especially oils, are likely to become exhausted within next 50 to 100 years resulting in the need to develop alternative sources of energy. Biological fuel generation may make an increasing contribution particularly in the conversion of renewable plant biomass to liquid and gaseous fuel. This plant biomass can be in the form of cultivated energy crops, natural vegetation, agricultural industrial and domestic organic wastes etc. Currently methane and ethanol are the main products, although other potential fuel can be generated using microorganisms including hydrogen, ethane, propane and butanol. 11
2.4. Choosing Microorganisms for Industrial use: Fermentation industries often prefer to use established GRAS (Generally Regarded As Safe) microorganisms, particularly for the manufacturing of food products and ingredients. This is because requirement for process approval using „new‟ microorganism are more stringent and associated costs are mush higher. Where pathogens and some genetically manipulated microorganisms are use as producers organisms additional safety measures must be taken. Here is the list of some GRAS microorganisms; Bacteria: Bacillus substilis. Lactobacillus bulgaricus. Lactococcus lactis. Leuconostoc oenos. Yeast: Candida utilis. Kluyveromyces marxianus. Kluyveromyces lactis. Saccharromyces cerevicae. Filamentous Fungi: Aspergillus niger. Aspergillus oryzae. Mucor javanicus. Penicillium roqueforti. 2.5. Isolation of suitable microorganism from the environment: There are two approaches; 1. Shotgun approach. 2. Objective approach. Shotgun Approach: In the shot gun approach the samples of free living microorganisms, biofilms or other microbial communities are collected from animals, plant materials, soils, sewage water and waste streams and particularly from unusual man made natural habitats. These isolates are then screened for desirable traits. Objective Approach: 11
In objective approach the sampling is carried out from specific sites where organisms with desired characteristics are considered to be likely components of natural micro flora. Once isolated for the pure culture, each micro organism must be screened for the desired property; production of specific enzymes, inhibitory compounds etc. However at this stage the level of activity or concentration of the target product is not of major concern as strain development can normally be employed to vastly improve performance, selected isolated must also be screened for other important features, such as stability and where necessary non toxicity. 2.6. Industrial micro organism Strains: Irrespective of the origin of an industrial micro organism, it should ideally exhibit: 1. Genetic stability. 2. Amenability to genetic manipulation. 3. Utilization of a wide range of low cost and readily available carbon sources. 4. Limited or no need of vitamins and additional growth factors. 5. Efficient production of the target product, whose route of biosynthesis should preferably be well characterized. 6. Safety, non pathogenicity and should not produce toxic agents 7. Ready harvesting from the fermentation. 8. Ready breakage, if the target product is intracellular. 9. Production of limited by products to ease subsequent purification problems. Strain Improvement: There are two major purposes for strain improvement ; 1. Increasing productivity. 2. Reducing the manufacturing costs. There are three main ways of strain improvement; 1. Natural recombination. 2. Mutation 3. Genetic Engineering. Conclusion: 1. A typical fermentation process includes upstream and downstream processing 12
2. Upstream processing includes production of microorganism, fermentation raw materials and fermentation. 3. Downstream processing includes product purification and product. 4. Fermentation products include High volume low value products like food stuff. Low volume high value products like fine chemicals and pharmaceuticals. 5. Microorganisms are used to provide a vast range of products and services. 6. Fermentation industries often prefer to use established GRAS (Generally Regarded As Safe) microorganisms 7. In the shot gun approach the samples of free living microorganisms, biofilms or other microbial communities are collected from animals, plant materials, soils, sewage water and waste streams and particularly from unusual man made natural habitats. 8. In objective approach the sampling is carried out from specific sites where organisms with desired characteristics are considered to be likely components of natural micro flora. 13
3. Fermentation media: 3.1. Media formulation: Most fermentations require liquid media, often referred to as broth, although some solid-substrate fermentations are operated. Fermentation media must satisfy all the nutritional requirements of the microorganism and fulfil the technical objectives of the process. The nutrients should be formulated to promote the synthesis of the target product, either cell biomass or a specific metabolite. In most industrial fermentation processes there are several stages where media are required. They may include several inoculum (starter culture) propagation steps, pilot-scale fermentations and the main production fermentation. Where biomass or primary metabolites are the target product, the objective is to provide a production medium that allows optimal growth of the microorganism. For secondary metabolite production, such as antibiotics, their biosynthesis is not growth related. Consequently, for this purpose, media are designed to provide an initial period of cell growth, followed by conditions optimized for secondary metabolite production. At this point the supply of one or more nutrients (carbon, phosphorus or nitrogen source) may be limited and rapid growth ceases. 3.2. Components of Fermentation Media: Most fermentations, except those involving solid substrates, require large quantities of water in which the medium is formulated. General media requirements include a carbon source, which in virtually all industrial fermentations provides both energy and carbon units for biosynthesis, and sources of nitrogen, phosphorus and sulphur. Other minor and trace elements must also be supplied, and some microorganisms require added vitamins, such as biotin and riboflavin. 14
Aerobic fermentations are dependent on a continuous input of molecular oxygen, and even some anaerobic fermentations require initial aeration of media, e.g. beer fermentations. Usually, media incorporate buffers, or the pH is controlled by acid and alkali additions, and antifoam agents may be required. For some processes, precursor, inducer or inhibitor compounds must be introduced at certain stages of the fermentation. 15
3.3. Composition of components in the fermentation media: This primarily involves consideration of the input of the carbon and nitrogen sources, minerals and oxygen, and their conversion to cell biomass, metabolic products, carbon dioxide, water and heat. From this information it should be possible to calculate the minimum quantities of each element required to produce a certain quantity of biomass or metabolite. Typically, the main elemental formula of microbial cells is approximately C4H7O2N, which on a basis of dry weight is 48% C, 7% H, 32% O and 14% N. Elemental composition varies slightly with growth rate, but the range is relatively small compared with interspecies differences, particularly between bacteria and fungi. Once the elemental requirements of a microorganism have been established, suitable nutrient sources can be incorporated into the media to fulfil these demands. To overcome this, intermittent or continuous addition of fresh medium may be carried out to maintain a relatively low concentration that is not repressive. Certain media nutrients or environmental conditions may affect not only the physiology and biochemistry, but also the morphology of the microorganism. Such morphological changes can influence product yield and other fermentation properties. 16
3.4. Selection of media: The media adopted also depend on the scale of the fermentation. For smallscale laboratory fermentations pure chemicals are often used in well-defined media. However, this is not possible for most industrial-scale fermentation processes, simply due to cost, as media components may account for up to 60–80% of process expenditure. Industrial-scale fermentations primarily use cost-effective complex substrates, where many carbon and nitrogen sources are almost undefinable. Most are derived from natural plant and animal materials, often byproducts of other industries, with varied and variable composition. 3.5. Key factors for the selection of media: The main factors that affect the final choice of individual raw materials are as follows. 1. Cost and availability: ideally, materials should be inexpensive, and of consistent quality and year round availability. 2. Ease of handling in solid or liquid forms, along with associated transport and storage costs, e.g. requirements for temperature control. 3. Sterilization requirements and any potential denaturation problems. 4. Formulation, mixing, complexing and viscosity characteristics that may influence agitation, aeration and foaming during fermentation and downstream processing stages. 5. The concentration of target product attained, its rate of formation and yield per gram of substrate utilized. 6. The levels and range of impurities, and the potential for generating further undesired products during the process. 7. Overall health and safety implications. 17
4. Carbon sources A carbon source is required for all biosynthesis leading to reproduction, product formation and cell maintenance. In most fermentations it also serves as the energy source. Carbon requirements may be determined from the biomass yield coefficient (Y), an index of the efficiency of conversion of a substrate into cellular material. Various organisms may exhibit different yield coefficients for the same substrate due primarily to the pathway by which the compound is metabolized. Differences can also be seen within an individual. For example, Saccharomyces cerevisiae grown on glucose has biomass yield coefficients of 0.56 and 0.12 g/g under aerobic and anaerobic conditions, respectively. As most carbon substrates also serve as energy sources, the organism‟s efficiency of both adenosine triphosphate (ATP) generation and its utilization are obviously additional key factors. Often, it is very useful, although rather difficult, to estimate how much ATP is required for growth. Carbohydrates are traditional carbon and energy sources for microbial fermentations, although other sources may be used, such as alcohols, alkanes and organic acids. Animal fats and plant oils may also be incorporated into some media, often as supplements to the main carbon source. 18
4.1. Molasses A byproduct of cane and beet sugar production, is a cheaper and more usual source of sucrose. This material is the residue remaining after most of the sucrose has been crystallized from the plant extract. It is a dark coloured viscous syrup containing 50–60% (w/v) carbohydrates, primarily sucrose, with 2% (w/v) nitrogenous substances, along with some vitamins and minerals. The carbohydrate concentration may be reduced during storage by contaminating microorganisms. A similar product, hydrol molasses, can also be used. This byproduct of maize starch processing primarily contains glucose. 4.2. MALT Aqueous extracts of malted barley can be concentrated to form syrups that are particularly useful carbon sources for the cultivation of filamentous fungi, yeasts and actinomycetes. Some cereal crops (especially barley) are soaked in water for their sprouting, which ultimately result in the activation of enzymes. The grains are removed from the water & they are dried for meshing. After meshing they are soaked in warm water. These cereals crops contain starch, which is converted to maltose by enzymes, this solution containing Maltose, is called wort. To remove water from wort, vaccum drying, or vapourization is performed, to make it concentrated this concentrated wort is known as malt. Malt extracts also contain some vitamins and approximately 5% nitrogenous substances, proteins, peptides and amino acids. Sterilization of media containing malt extract must be carefully controlled to prevent over-heating. 19
4.3. Maillard reaction The reaction takes place between amino group of amino acids, with the carbonyl groups of reducing sugars, ketones and aldehydes. Maillard reaction products are brown condensation products, Not only does this cause colour change, but it also results in loss of fermentable materials and some reaction products may inhibit microbial growth. 4.4. Starch and dextrin These polysaccharides are not as readily utilized as monosaccharides and disaccharides, but can be directly metabolized by amylase-producing microorganisms, particularly filamentous fungi. Their extracellular enzymes hydrolyse the substrate to a mixture of glucose, maltose or maltotriose to produce a sugar spectrum similar to that found in many malt extracts. Maize starch is most widely used, but it may also be obtained from other cereal and root crops. To allow use in a wider range of fermentations, the starch is usually converted into sugar syrup, containing mostly glucose. It is first gelatinized and then hydrolysed by dilute acids or amylolytic enzymes, often microbial glucoamylases that operate at elevated temperatures. 21
4.5. Sulphite waste liquors: Sugar containing wastes derived from the paper pulping industry are primarily used for the cultivation of yeasts. Waste liquors from coniferous trees contain 2–3% (w/v) sugar, which is a mixture of hexoses (80%) and pentoses (20%). Hexoses include glucose, mannose and galactose, whereas the pentose sugars are mostly xylose and arabinose. Those liquors derived from deciduous trees contain mainly pentoses. Usually the liquor requires processing before use as it contains sulphur dioxide. The low pH is adjusted with calcium hydroxide or calcium carbonate, and these liquors are supplemented with sources of nitrogen and phosphorus. 21
4.6. Cellulose: Cellulose is predominantly found as lignocellulose in plant cell walls, which is composed of three polymers: cellulose, hemicellulose and lignin. Lignocellulose is available from agricultural, forestry, industrial and domestic wastes. Relatively few microorganisms can utilize it directly, as it is difficult to hydrolyse. The cellulose component is in part crystalline, encrusted with lignin, and provides little surface area for enzyme attack. At present it is mainly used in solid-substrate fermentations to produce various mushrooms. However, it is potentially a very valuable renewable source of fermentable sugars once hydrolysed, particularly in the bioconversion to ethanol for fuel use. 4.7. Whey: Whey is an aqueous byproduct of the dairy industry. This material is expensive to store and transport. Therefore, lactose concentrates are often prepared for later fermentation by evaporation of the whey, following removal of milk proteins for use as food supplements. Lactose is generally less useful as a fermentation feedstock than sucrose, as it is metabolized by fewer organisms. S. cerevisiae, for example, does not ferment lactose. This disaccharide was formerly used extensively in penicillin fermentations and it is still employed for producing ethanol, single cell protein,lactic acid, xanthangum, vitamin B12 and gibberellic acid. 22
4.8. Alkanes and alcohols: n-Alkanes of chain length C10–C20 are readily metabolized by certain microorganisms. Mixtures, rather than a single compound, are usually most suitable for microbial fermentations. However, their industrial use is dependent upon the prevailing price of petroleum. Methane is utilized as a carbon source by a few microorganisms, but its conversion product methanol is often preferred for industrial fermentations as it presents fewer technical problems. High purity methanol is readily obtained and it is completely miscible with water. Methanol has high percent carbon content and is relatively cheap, although only a limited number of organisms will metabolize it. During fermentations on methanol, the oxygen demand and heat of fermentation are high, but this is even more problematic when growing on alkanes. Ethanol is less toxic than methanol and is used as a sole or co-substrate by many microorganisms, but it is too expensive for general use as a carbon source. However, its biotransformation to acetic acid by acetic acid bacteria remains a major fermentation process. 23
4.9. Fats and oils: Hard animal fats that are mostly composed of glycerides of palmitic and stearic acids are rarely used in fermentations. However, plant oils (primarily from cotton seed, linseed, maize, olive, palm, rape seed and soya) and occasionally fish oil, may be used as the primary or supplementary carbon source, especially in antibiotic production. Plant oils are mostly composed of oleic and linoleic acids, but linseed and soya oil also have a substantial amount of linolenic acid. The oils contain more energy per unit weight than carbohydrates. In addition, the carbohydrates occupy a greater volume, because they are usually prepared as aqueous solutions of concentrations no greater than 50% (w/w). Consequently, oils can be particularly useful in fed-batch operations, as less spare capacity is needed to accommodate further additions of the carbon source Conclusion: 1. A carbon source is required for all biosynthesis leading to reproduction, product formation and cell maintenance 2. Molasses is a byproduct of cane and beet sugar production, is a cheaper and more usual source of sucrose. hydrol molasses is byproduct of maize starch processing primarily contains glucose. 3. MALT is aqueous extracts of malted barley can be concentrated to form syrups for the cultivation of filamentous fungi, yeasts and actinomycetes. 4. Maillard reaction products are brown condensation products, not only does this cause colour change, but it also results in loss of fermentable materials and some reaction products may inhibit microbial growth. 5. Starch and dextrins are not as readily utilized as monosaccharides and disaccharides, but can be directly metabolized by amylase-producing microorganisms. 24
6. Sulphite waste liquor is sugar containing wastes derived from the paper pulping industry are primarily used for the cultivation of yeasts. 7. Cellulose is predominantly found as lignocellulose in plant cell walls, which is composed of three polymers: cellulose, hemicellulose and lignin. It use in the bioconversion to ethanol for fuel use. 8. Whey is an aqueous byproduct of the dairy industry, it is expensive to store and transport. Lactose concentrates in penicillin fermentations and it is still employed for producing ethanol, single cell protein, lactic acid, xanthangum, vitamin B12 and gibberellic acid. 9. Methane is utilized as a carbon source by a few microorganisms, but its conversion product methanol is often preferred for industrial fermentations as it presents fewer technical problems. Ethanol is less toxic than methanol and is used as a sole or co-substrate by many microorganisms, but it is too expensive for general use as a carbon source. 10. The oils contain more energy per unit weight than carbohydrates. In addition, the carbohydrates occupy a greater volume, because they are usually prepared as aqueous solutions of concentrations no greater than 50% (w/w). 25
5. Nitrogen sources Most industrial microbes can utilize both inorganic and organic nitrogen sources. Inorganic nitrogen may be supplied as ammonium salts, often ammonium sulphate and diammonium hydrogen phosphate, or ammonia. Ammonia can also be used to adjust the pH of the fermentation. Organic nitrogen sources include amino acids, proteins and urea. Nitrogen is often supplied in crude forms that are essentially byproducts of other industries, such as corn steep liquor, yeast extracts, peptones and soya meal. Purified amino acids are used only in special situations, usually as precursors for specific products. 5.1. Corn steep liquor Corn steep liquor is a byproduct of starch extraction from maize and its first use in fermentations was for penicillin production in the 1940s. The exact composition of the liquor varies depending on the quality of the maize and the processing conditions. Concentrated extracts generally contain about 4% (w/v) nitrogen, including a wide range of amino acids, along with vitamins and minerals. Any residual sugars are usually converted to lactic acid (9–20%, w/v) by contaminating bacteria. Corn steep liquor can sometimes be replaced by similar liquors, such as those derived from potato starch production. 26
5.2. Yeast extracts Yeast extracts may be produced from waste baker‟s and brewer‟s yeast, or other strains of S. cerevisiae. Alternate sources are Kluyveromyces marxianus (formerly classified as K. fragilis) grown on whey and Candida utilis cultivated using ethanol, or wastes from wood and paper processing. Those extracts used in the formulation of fermentation media are normally salt-free concentrates of soluble components of hydrolysed yeast cells. Yeast extracts with sodium chloride concentrations greater than 0.05% (w/v) cannot be used in fermentation processes due to potential corrosion problems. Yeast cell hydrolysis is often achieved by autolysis, 27
using the cell‟s endogenous enzymes, usually without the need for additional hydrolytic enzymes. Autolysis can be initiated by temperature or osmotic shock, causing cells to die but without inactivating their enzymes. Temperature and pH are controlled throughout to ensure an optimal and standardized autolysis process. Temperature control is particularly important to prevent loss of vitamins. Autolysis is performed at 50–55°C for several hours before the temperature is raised to 75°C to inactivate the enzymes. Finally, the cells are disrupted by plasmolysis or mechanical disruption. Cell wall materials and other debris are removed by filtration or centrifugation and the resultant extract is rapidly concentrated. Extracts are available as liquids containing 50–65% solids, viscous pastes or dry powders. They contain amino acids, peptides, watersoluble vitamins and some glucose, derived from the yeast storage carbohydrates (trehalose and glycogen). 28
5.3. Peptones Peptones are usually too expensive for large-scale industrial fermentations. They are prepared by acid or enzyme hydrolysis of high protein materials: meat, casein, gelatin, keratin, peanuts, soy meal, cotton seeds, etc. Their amino acid compositions vary depending upon the original protein source. For example, gelatin derived peptones are rich in proline and hydroxyproline, but are almost devoid of sulphur-containing amino acids; whereas keratin peptone is rich in both proline and cystine, but lacks lysine. Peptones from plant sources invariably contain relatively large quantities of carbohydrates. 29
5.4. Soya bean meal Residues remaining after soya beans have been processed to extract the bulk of their oil are composed of 50% protein, 8% non-protein nitrogenous compounds, 30% carbohydrates and 1% oil. This residual soya meal is often used in antibiotic fermentations because the components are only slowly metabolized, thereby eliminating the possibility of repression of product formation. 31
Conclusion: 1. Corn steep liquor is a byproduct of starch extraction and use in penicillin fermentations 2. Yeast extracts may be produced from waste baker‟s and brewer‟s yeast, or other strains of S. cerevisiae. Yeast cell hydrolysis is often achieved by autolysis, using the cell‟s endogenous enzymes, usually without the need for additional hydrolytic enzymes. 3. Peptones are usually too expensive for large-scale industrial fermentations. They are prepared by acid or enzyme hydrolysis of high protein materials such as meat, casein, gelatin, keratin, peanuts, soy meal, cotton seeds, etc. 4. Soya bean meal is often used in antibiotic fermentations because the components are only slowly metabolized, thereby eliminating the possibility of repression of product formation. 31
6. Essential Components of Fermentation Media 6.1. Water All fermentation processes, except solid-substrate fermentations, require vast quantities of water. In many cases it also provides trace mineral elements. Not only is water a major component of all media, but it is important for ancillary equipment and cleaning. A reliable source of large quantities of clean water, of consistent composition, is therefore essential. Before use, removal of suspended solids, colloids and microorganisms is usually required. When the water supply is „hard‟, it is treated to remove salts such as calcium carbonate. Iron and chlorine may also require removal. For some fermentations, notably plant and animal cell culture, the water must be highly purified. 6.2. Minerals Normally, sufficient quantities of cobalt, copper, iron, manganese, molybdenum, and zinc are present in the water supplies, and as impurities in other media ingredients. For example, corn steep liquor contains a wide range of minerals that will usually satisfy the minor and trace mineral needs. Occasionally, levels of calcium, magnesium, phosphorus, potassium, sulphur and chloride ions are too low to fulfil requirements and these may be added as specific salts. 32
6.3. Vitamins and growth factors Many bacteria can synthesize all necessary vitamins from basic elements. For other bacteria, filamentous fungi and yeasts, they must be added as supplements to the fermentation medium. Most natural carbon and nitrogen sources also contain at least some of the required vitamins as minor contaminants. Other necessary growth factors, amino acids, nucleotides, fatty acids and sterols, are added either in pure form or, for economic reasons, as less expensive plant and animal extracts. 6.4. Precursors Some fermentations must be supplemented with specific precursors, notably for secondary metabolite production. When required, they are often added in controlled quantities and in a relatively pure form. Examples include phenylacetic acid or phenylacetamide added as side-chain precursors in penicillin production. Dthreonine is used as a precursor in l-isoleucine production by Serratia marsescens, 33
and anthranillic acid additions are made to fermentations of the yeast Hansenula anomala during l-tryptophan production. 6.5. Inducers and elicitors If product formation is dependent upon the presence of a specific inducer compound or a structural analogue, it must be incorporated into the culture medium or added at a specific point during the fermentation. In plant cell culture the production of secondary metabolites, such as flavonoids and terpenoids, can be triggered by adding elicitors. These may be isolated from various microorganisms; particularly plant pathogens. Inducers are often necessary in fermentations of genetically modified microorganisms (GMMs). This is because the growth of GMMs can be impaired when the cloned genes are „switched on‟, due to the very high levels of their transcription and translation. Consequently, inducible systems for the cloned genes are incorporated that allow initial maximization of growth to establish high biomass density, whereupon the cloned gene can then be „switched on‟ by the addition of the specific chemical inducer. 34
6.6. Inhibitors Inhibitors are used to redirect metabolism towards the target product and reduce formation of other metabolic intermediates; others halt a pathway at a certain point to prevent further metabolism of the target product. An example of an inhibitor specifically employed to redirect metabolism is sodium bisulphite, which is used in the production of glycerol by S. cerevisiae Some GMMs contain plasmids bearing an antibiotic resistance gene, as well as the heterologous gene(s). The incorporation of this antibiotic into the medium used for the production of the heterologous product selectively inhibits any plasmid-free cells that may arise. 6.7. Cell permeability modifiers These compounds increase cell permeability by modifying cell walls and/or membranes, promoting the release of intracellular products into the fermentation medium. Compounds used for this purpose include penicillins and surfactants. They 35
are frequently added to amino acid fermentations, including processes for producing L-glutamic acid using members of the genera Corynebacterium and Brevibacterium. 6.8. Oxygen Depending on the amount of oxygen required by the organism, it may be supplied in the form of air containing about 21% (v/v) oxygen, or occasionally as pure oxygen when requirements are particularly high. The organism‟s oxygen requirements may vary widely depending upon the carbon source. For most fermentations the air or oxygen supply is filter sterilized prior to being injected into the fermenter. 36
6.9. Antifoams Antifoams are necessary to reduce foam formation during fermentation. Foaming is largely due to media proteins that become attached to the air–broth interface where they denature to form a stable foam. If uncontrolled the foam may block air filters, resulting in the loss of aseptic conditions; the fermenter becomes contaminated and microorganisms are released into the environment. Of possibly most importance is the need to allow „freeboard‟ in fermenters to provide space for the foam generated. If foaming is minimized, then throughputs can be increased. There are three possible approaches to controlling foam production: modification of medium composition, use of mechanical foam breakers and addition of chemical antifoams. Chemical antifoams are surface active agents which reduce the surface tension that binds the foam together. The ideal antifoam should have the following properties: 1. Readily and rapidly dispersed with rapid action; 2. High activity at low concentrations; 3. Prolonged action; 4. Non-toxic to fermentation microorganisms, humans or animals; 5. low cost; 6. Thermostability; 7. Compatibility with other media components and the process, i.e. having no effect on oxygen transfer rates or downstream processing operations. Natural antifoams include plant oils (e.g. from soya, sunflower and rapeseed), deodorized fish oil, mineral oils and tallow. The synthetic antifoams are mostly silicon oils, poly alcohols and alkylated glycols. Some of these may adversely affect downstream processing steps, especially membrane filtration. 37
Conclusions: 1. All fermentation processes, except solid-substrate fermentations, require vast quantities of water. In many cases it also provides trace mineral elements. 2. Normally, sufficient quantities of cobalt, copper, iron, manganese, molybdenum, and zinc are present in the water supplies, and as impurities in other media ingredients. 3. Many bacteria can synthesize all necessary vitamins from basic elements. Other necessary growth factors are added either in pure form. 4. Some fermentations must be supplemented with specific precursors. Phenylacetic acid or phenylacetamide added as side-chain precursors in penicillin production. Dthreonine is used as a precursor in L-isoleucine production. 38
5. If product formation is dependent upon the presence of a specific inducer compound, it must be incorporated into the culture medium or added at a specific point during the fermentation. 6. Inhibitors are used to redirect metabolism towards the target product and reduce formation of other metabolic intermediates; others halt a pathway at a certain point to prevent further metabolism of the target product. For example, sodium bisulphite, is used in the production of glycerol. 7. Cell permeability modifiers promoting the release of intracellular products into the fermentation medium such as penicillins and surfactants. 8. The organism‟s oxygen requirements may vary widely depending upon the carbon source. oxygen supply is filter sterilized prior to being injected into the fermenter. 9. Chemical antifoams are surface active agents which reduce the surface tension to reduce foam formation during fermentation. There are three possible approaches to controlling foam production, modification of medium composition, use of mechanical foam breakers and addition of chemical antifoams. 39
7. Fermentation systems Microbiologists use the term fermentation in two different contexts. First, in metabolism, fermentation refers to energy-generating processes where organic compounds act as both electron donor and acceptor. Second, in the context of industrial microbiology, the term also refers to the growth of large quantities of cells under aerobic or anaerobic conditions, within a vessel referred to as a fermenter or bioreactor. Objectives of growing large quantities of cells; 1. For the growth of cell (plant, animals etc) 2. To produce enzymes. 3. To produce specific metabolite. 4. And for transformation. It must be remembered that, particularly with the advent of recombinant DNA technology, alternate systems for producing specific cell products are now available. Monoclonal antibodies are already extracted from the ascitic fluid of rodents vaccines can be produced in sheep‟s milk or in fruit (e.g. biosynthesis of malaria vaccine in bananas) and various other recombinant products may be manufactured in agricultural plants. 41
7.1. Examples of Fermentation Alcoholic Fermentation In alcoholic fermentation Pyruvate molecule is converted into Acetaldehyde which is further converted to into ethanol. Homolactic Fermentation In this type of fermentation Pyruvate is converted to lactate, releasing energy. Heterolactic Fermentation Glucose is converted to pyruvate, carbon dioxide and acetyle phosphate, the pyruvate further converts to lactate and acetyle phospate converts to Acetyl Co A which is further converted to Acetaldehyde, and it is converted to ethanol by the release of NAD. 2-3 Butandiole Fermentation 2-pyruvate is converted to Acetolactate which converts to Acetoin, and it converted to produce 2, 3 Butandiole. 7.2. Two broad categories of fermentation 1. Solid State Fermentation 41
Micro organisms grow on solid surface with little water, or no water. It can be aerobic or anaerobic. The typical example of Aerobic fermentation is Cheese production, and the typical example of Anaerobic fermentation is, fermented meat products like, salami. 2. Submerged Fermentation Substances or substrates are dissolved in water to prepare a homogenous mixture, which is known as Broth. It can be aerobic or anaerobic. The typical example of Aerobic fermentation is Antibiotics production. and the typical example of Anaerobic fermentation is alocholic, beer and wine production. 7.3. Fermentation Process Fermentation on the Basis of Culture: Fermentation process can be broadly divided into two major types; Monoculture Fermentation: In this type of fermentation only one type of culture is needed. It is also known as Mono-septic fermentation. For example, production of antibiotics or enzymes. Poly-culture Fermentation: In this type of fermentation more than one type of culture is needed. It is also called Mixed culture fermentation. For example, biological wastes treatment. 42
7.4. Fermentation can be septic or aseptic Aseptic Fermentation Septic Fermentation In aseptic fermentation cleaning or Septic sterilization is not a major issue. fermentation needs cleaning along with clean environment, so there is a need of sterilization Examples of aseptic fermentation Examples of septic fermentation include include, waste treatment, acidification of vaccine production, enzymes or vitamins ethanol to acetic acid & mushroom production etc. production In Septic fermentation the fermenter can be made up of, glass or steel, which should be non-toxic, and non- corrosive. In Aseptic fermentation there is no need of sterilization, so some fermenters are made up woods. 43
7.5. Classification of fermentation on the basis of organization of biological system: There are two categories, suspended growth fermentation, spotted growth fermentation. Spotted Growth Fermentation Suspended Growth Fermentation In spotted growth, cells are freely In suspended growth cells are freely dispersed but their growth is spotted. dispersed in the medium In spotted growth microbes live in groups In suspended growth the individual to form bio-films which are formed on microorganisms forms a group in a non-living surfaces and perform specific medium, which is known as flocculation. functions. Spotted growth can be of two types; Due to flocculation nutrient variation may Fixed film system, having a fixed film on occur which liquid moves, and in produces fermenter. specific product, for example vinegar production. Fluidized System, in which the bio film is dipped in the fermentation medium, it is mostly used in water treatments 44 the different regions of
7.6. Fermenter Design and Construction: Fermenter is a vessel which provides suitable environmental conditions, to achieve the desired product. Fermentor is where the microbiology process takes place. Any large-scale reaction is referred to as a fermentation. Most are aerobic processes. Fermentors vary in size from 5 to 500,000 liters. Aerobic and anaerobic fermentors. Large-scale fermentors are almost always stainless steel. Impellers and spargers supply oxygen Objectives: 1. It should maintain high concentration or high density of cells. 2. Several chemical or physical components (like temperature, pH, Oxygen etc,) vary from culture to culture, product to product, and from the scale of fermentation, for example, lab scale, or industrial scale fermentation. They should be taken under consideration. Parameters for the fermentation design: 1. Target Microorganism. 2. Desired metabolite. 3. Loss of metabolite. 4. And, Scale of fermentation. 45
Conclusion: 1. Examples of fermentation include alcoholic fermentation, homolactic fermentation, heterolactic fermentation and butandiole Fermentation 2. categories of fermentation include solid state fermentation and submerged fermentation. 3. Fermentation on the basis of culture divided into monoculture fermentation and Poly-culture fermentation. 4. Fermentation can be septic or aseptic. There are two categories, suspended growth fermentation, spotted growth fermentation. 46
8. Modes of Fermentations Industrial fermentations may be carried out either batch-wise, as fed - batch operations, or as continuous cultures 8.1. Batch Culture Fermentation: In batch processing a batch of culture medium in the fermenter is inoculated with a microbial culture, or the “starter culture.” The fermentation proceeds for a certain duration (the “batch time” or “fermentation time”) and the product is harvested. Batch fermentations typically extend over 4 – 5 days, but some traditional food fermentations may last for months. Advantages: 1. Normally used for producing secondary metabolites. 2. Initial cost is low. 3. And, if we suspect any contamination we can stop it, & wash it for re-use. Disadvantages: 1. Not ideal for the production of primary metabolites. 2. Have got batch to batch variation in the product. 3. Product is produced at specific stage, and so its concentration becomes constant. 4. Due to continuous sterilization the sensors of oxygen. pH, or temperature can be affected. 5. And it is very, laborious 8.2. Fed - batch Fermentations: In fed - batch fermentations, sterile culture medium is added either continuously or periodically to the inoculated fermentation batch. The volume of the fermenting broth 47
increases with each addition of the medium. The batch is harvested after the batch time. The composition of the feeding medium may vary with time. Advantages: 1. Suitable for primary metabolites production. 2. Substrate is metabolized rapidly. 3. Viscosity can be decreased by the addition of fermentation medium. 4. And, toxic compounds are diluted. Disadvantages: 1. We have to take the samples at regular intervals to check the concentration of the substrate. 2. Its fermentation time is high as compare to the batch culture fermentation. 8.3. Continuous fermentations: In continuous fermentations, sterile medium is fed continuously into a fermenter and the fermented product is continuously withdrawn, so the fermentation volume remains unchanged. Typically, continuous fermentations are started as batch cultures and feeding begins after the microbial population has reached a certain concentration. In some continuous fermentations, a small part of harvested culture may be recycled, to continuously inoculate the sterile feed medium entering the fermentation. Sometimes the concentration of biomass become low, and the medium concentration is high, this is because we are continuously removing the biomass from the fermenter. To solve this problem we use the membrane that separates the biomass from the liquid portion, & the biomass can then be reused. Advantages: 1. Suitable for primary growth, or related metabolites. 2. Reduces downstream processing time. 48
Disadvantages; 1. System is highly expensive. 2. There is a high risk of contamination during long fermentation 8.4. List of Industrial Microorganisms: There are thirteen different categories in w!hich micro organisms are used; 1. Traditional products. 2. Agricultural products. 3. Aminoacids. 4. Enzymes. 5. Fuel & chemical feed stocks. 6. Nucleotisdes. 7. Organic acid. 8. Pharceuticals. 9. Hormones 10. Immunosupperants. 11. Vitamins. 12. Ploymers. 13. Single cell proteins. Conclusions: Industrial fermentations may be carried out either batch-wise, as fed batch operations, or as continuous cultures. 49
9. Industrial products 9.1. Fuels and industrial chemicals Within the next 50–100 years some fossil fuel supplies, particularly oil, are likely to become depleted. Consequently, there is an urgent need to develop alternate energy sources. Most requirements will be met from geothermal, nuclear, solar, water and wind sources. However, biological fuel generation is likely to become increasingly important, especially as it can provide both liquid and gaseous fuels. Importantly, these fuels are produced from renewable resources, primarily plant biomass, in the form of cultivated energy crops, natural vegetation, and agricultural, domestic and industrial wastes. The two main microbial fuel products currently derived from these resources are methane and ethanol, but these are not the only fuels that can be formed. Other liquid and gaseous examples include hydrogen, propane, methanol and butanol; electricity can also be generated by microbiological systems. Numerous other important chemical compounds are now most economically produced by microbial fermentation and biotransformation processes. The majority are primary metabolites that include organic acids, amino acids, industrial solvents and a wide range of biopolymers. Many of these microbial products are used as chemical feed stocks and functional ingredients in a wide range of industrial and food products. Alkanes Methane production from organic materials involves three specific phases. First, a group of microorganisms hydrolyse organic polymers, including fats, proteins and polysaccharides, to their respective soluble monomers. These compounds are then metabolized to organic acids by anaerobic acidogenic organisms. In the final phase, the organic acids are converted to alkanes and carbon dioxide. Methanogenic bacteria produce methane from acetate, which is the major product. Butanol Acetone, butanol, butyric acid and isopropanol, along with other organic acids and alcohols, may be obtained by clostridial fermentation of a range of raw materials, including starch, molasses and hydrolysed cellulosic materials. The relative amount of each fermentation product is dependent upon the bacterial species and the specific 51
strain used, and the environmental conditions of the fermentation. There are three main fermentation types: 1 acetone–butanol (Clostridium acetobutylicum), additional products: butyric acid, acetic acid, acetoin, ethanol, CO2 and H2; 2 butanol–isopropanol (Clostridium butylicum), additional products: butyric acid, acetic acid, CO2 and H2; and 3 butyric acid–acetic acid (Clostridium butyricum),additional products: CO2 and H2. Industrial ethanol . The ethanol was produced by fermentation of sucrose, derived from sugar cane, using Saccharomyces cerevisiae. Brazil is now responsible for over 46% of annual world production. Apart from sucrose, other conventional fermentation substrates for ethanol fermentations include simple sugars derived from plants and dairy wastes. Hydrogen Hydrogen is a very attractive fuel because of its high energy content (118.7 kJ/g), which is about four-fold greater than ethanol and over two-fold higher than methane. The technology for its use has already been developed and the product of its combustion is water. A wide range of microorganisms produce hydrogen as a part of mechanisms for disposing of electrons that are generated during metabolic reactions 51
The generation of hydrogen using microorganisms, or cell-free systems based on microbial components, is still very much in its infancy. 9.2. Amino acids Several amino acids are produced in commercial quantities via direct fermentation processes using overproducing microbial strains, or by microbial biotransformation. They are mostly employed as food or animal feed supplements and flavour compounds. However, several amino acids also have uses in pharmaceuticals and cosmetics, and in the chemical industry for the manufacture of polymers. L- Glutamic acid Of all the amino acid production processes, that of L-glutamic acid is probably the most important in terms of quantity. Its main use is as the flavour enhancer, monosodium L- glutamate (MSG), which can heighten and intensify the flavour of foods without adding significant flavour of its own. MSG is naturally present in certain foods and was discovered to be the „active‟component of a traditional flavourenhancing seaweed stock used in Far Eastern foods. Glutamic acid-producing microorganisms include species of the closely related genera Arthrobacter, Brevibacterium, Corynebacterium, Microbacterium and Micrococcus. These are Gram-positive, biotinrequiring, non-motile bacteria that have intense glutamate dehydrogenase activity. 52
L-Glutamic acid biosynthesis in mutant strains. 9.3. Organic acids Organic acids are produced by through metabolisms of carbohydrates. They accumulate in the broth of the fermenter from where they are separated and purified. 1.Terminal end products ( lactic acid, (pyruvate, alcohol), Propionic acid 2. Incomplete oxidation of sugars (citric acid, Itaconic acid, Gluconic acid 3. Dehydrogenation of alcohol (acetic acid) Acetic acid fermentation The acetic acid fermentation is a highly aerobic process, essentially a biotransformation by acetic acid bacteria, involving incomplete oxidation of ethanol to acetic acid. Industrial acetic acid bacteria are members of the genera Acetobacter and Gluconobacter, mostly A. aceti, A. europaeus, A. hansenii, A. rancens, A. xylinum and G. oxydans. Citric acid 53
Citric acid is widely used in the food industry as an acidulant and flavouring agent in beverages, confectionery and other foods, and in leavening systems for baked goods. As a food constituent, its use is unrestricted because it has GRAS status. This organic acid also has many non-food applications. Strains that can tolerate high sugar and low pH with reduced synthesis of undesirable by products (oxalic acid, isocitric acid, gluconic acid) such as Aspergillus niger, clavatus Pencillium luteum. Citric acid biosynthesis CITRIC ACID: industrial uses 1. Flavoring agent in food and beverages, Jams, candies, deserts, frozen fruits, soft drinks, wine, antioxidants and preservative 2. Chemical industry:antifoam, treatment of textiles, metal industry, pure metals , citrate (chelating agent) 3. Agent for stabilization of Fats, oil or ascorbic acid Stabilizer for cheese preparation 4. Pharmaceutical industry, Trisodium citrate (blood preservative), Preservation of ointments and cosmetics, Source of iron 5. Detergent cleaning industry, Replace polyphosphates Gluconic acid Calcium gluconate and ferrous gluconate are widely used as therapeutic agents to treat patients with calcium and iron deficiency. The free acid is also used as a mild acidulant in the tanning industry. Over 50 000 tonnes of gluconic acid are produced each year using A. niger grown in submerged fermentations on glucose and corn steep liquor, under both phosphate and nitrogen limitation. These highly aerobic fermentations are performed at pH 6–7 and 30°C. They last for 20 h and achieve yields of over 90%. 54
Itaconic acid This dicarboxylic acid is used in the manufacture of adhesives, paper products and textiles. It is also incorporated into plastics as a copolymer with acrylic acid, methyl acrylate and styrene . Itaconic acid is produced commercially by submerged culture of Aspergillus terreus or A. itaconicus, often using molasses and corn steep liquor, with product yields of up to 65%. The 3-day fermentation must be highly aerated and operated at a relatively high temperature of 35–42°C. Itaconic acid is formed in a branch of the TCA cycle via decarboxylation of cis-aconitate (Fig. 10.12), which is normally followed by its oxidation to itatartaric acid. Onward metabolism of itaconic acid must be prevented in commercial fermentations, otherwise yield is reduced. This is achieved by formulating the medium with high levels of calcium ions, thereby inhibiting itaconic acid oxidase, which catalyses the oxidation of itaconic acid to itatartaric acid. Itaconic acid biosynthesis. Lactic acid LACTIC ACID: industrial uses 1.Technical grade 20-50%; Ester manufacture,Textile industry 2.Food grade >80%; Food additive (sour flour and dough) 3. Pharmaceutical grade >90%; Intestinal treatment; (metal ion lactates) - Lactic acid was the first microbial product of acids . The process carried out under anaerobic conditions. The fermentation carried out for about 3 days in presence of 55
CaCO3 which react with lactic acid to give difficulty soluble calcium lactate where the lactic acid is toxic for the bacteria used. When the fermentation is completed , the fermentation liquor is heated to dissolve the difficulty soluble calcium lactate , the heated broth is then filtered to remove the excess CaCO3 and the filtrate is left to cool where needle like crystals of calcium lactate are formed. The process of heating and re-crystallization is repeated several times. After that dil H2SO4 is added to the dissolved Ca-lactate while the solution is still hot, CaSO4 is precipitated and lactic acid remains in the supernatant . Kojic acid Kojic acid is produced by several species of fungi, especially Aspergillus oryzae, which has the Japanese common name koji. Kojic acid is a by-product in the fermentation process of malting rice, for use in the manufacturing of sake, the Japanese rice wine. It is a mild inhibitor of the formation of pigment in plant and animal tissues, and is used in food and cosmetics to preserve or change colors of substances. Kojic acid, is a white or cream-colored acicular crystal. It easily dissolves in water, and organic solvents. It a chelation agent for zinc, copper, nickel, cobalt, iron, manganese, Kojic acid Main use and application: 1. Daily chemicals material: Because of its slow and effective reversible competitive inhibition of human melanocyte tyrosinase, kojic acid prevents melanin formation. Kojic acid and it's derivatives are widely used in high-quality brightening cosmetic, bath cream, Kojic acid soap, tooth paste. 2. Medicine material: Kojic acid and it's derivatives are used as an important material in antibiotic - cethamycin, anodyne, and antiphlogistic production 3. Food additive: Kojic acid and it's derivatives work as antiseptic, antioxidant, preservative and color stabilizer in meat processing, also act as useful materials of food aromatize - maltol and ethyimaltol. 4. Preservative and color stablizer of cut-flower: Kojic acid and it's derivatives are added to cub-flower to keep the flower colorful and fresh. 5. Iron analysis reagent (It forms a bright red complex with ferric ions) 6. Non-toxic to person and livestock, pollution-free pesticide in insecticide production. Production of Kojic acid :56
13 C-Labeling studies have revealed at least two pathways to kojic acid. In the usual route, dehydratase enzymes convert glucose to kojic acid. Pentoses are also viable precursors in which case dihydroxyacetone is invoked as an intermediate. 9.4. Enzymes Commercial microbial enzymes are increasingly replacing conventional chemical catalysts in many industrial processes. Advantages of Enzymes over Chemical Catalysts: 1. The ability to function under relatively mild conditions of temperature, pH and pressure. 2. There is usually no requirement for expensive corrosion-resistant equipment. 3. Enzymes are specific, often stereo selective, catalysts, which do not produce unwanted byproducts. 4. There is less need for extensive refining and purification of the target product. 5. Compared with chemical processes, enzyme-based processes are „environmentally friendly‟ as enzymes are biodegradable and there are fewer associated waste disposal problems. 57
Enzymes can be used in two forms; Enzymes Only. Microbes/ Cell form. We can use any specific enzymes Suspended or immobilized microbial directly for the production of desired cells and spores product. may be employed as biocatalysts in some industrial particularly where bioconversions, coenzymes are necessary. Pure enzymes have following Have following limitations; advantages; Multi enzyme systems could provide The cells „waste‟ energy and resources more efficient substrate utilization. in growth and /or maintenance activities. Have higher yields and greater product Side reactions may lead to a reduction uniformity. in the potential yield of the target product. Several thousand tonnes of commercial Conditions for microbial growth, where enzymes are currently produced each required, year, which have a value in excess of may be different from those necessary US$1500 million. for optimum product formation. Most commercial enzymes are now Difficulties may be encountered in the obtained from microbial sources. Many isolation and purification of the product of these are extracellular enzymes, with from the cells or spent fermentation the majority being derived from various medium. species of Bacill 58
Percentage of Enzymes Usage in Industries: Enzymes Bulk Enzymes: Mostly used in crude preparations. Fine Enzymes: It is the highly pure form of enzymes. Mostly used in clinical, therapeutic and food products. Its Downstream processing cost is high. To reduce cost we fix those enzymes on solid surface, and immobilize them so we can re-use them. Some enzymes are stable in this form and no further purification is required. Recently the mostly used enzyme in Molecular biology is Thermus aquaticus (Taq DNA Polymerase), It can also be produced by Pyrococcus Furosus (Pfu DNA Polymerase). 59
Enzyme Production/Isolation Methods The structural complexity of enzymes makes their synthetic preparation a formidable task. They are natural products that are isolated/produced from three principle sources. Isolation from animal organs (hog insulin), Isolation from plant material (papain), Microorganism production. The structural complexity of enzymes makes their synthetic preparation a formidable task. Isolation and purification are complicated by the presence of similar proteins and the inherent sensitivity of enzymes to pH, temperature and degradation by other enzymes. 61
Detergent enzymes Unlike other detergent components, enzymes do not have a negative impact on sewage treatment processes. They are totally and rapidly biodegraded to leave no harmful residues. Consequently, they are environmentally safe and are no risk to aquatic life. The first commercial use of
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