EntranceBiotechnology objects. Industrial use of microorganisms Microorganisms are used in biotechnology because they
In the food industry, microorganisms are used to produce a number of products. Thus, alcoholic drinks - wine, beer, cognac, alcohol - and other products are produced using yeast. The baking industry uses yeast and bacteria, the dairy industry uses lactic acid bacteria, etc.
Among the variety of processes caused by microorganisms, one of the most important is fermentation.
Fermentation refers to the transformation of carbohydrates and some other organic compounds into new substances under the influence of enzymes produced by microorganisms. Known different kinds fermentation. They are usually named after the end products formed during the fermentation process, for example, alcohol, lactic acid, acetic acid, etc.
Many types of fermentation - alcoholic, lactic acid, acetone butyl, acetic acid, citric acid and others, caused by various microorganisms, are used in industry. For example, yeast is used in the production of ethyl alcohol, bread, beer, and wine; in the production of citric acid – molds; in the production of acetic and lactic acids, acetone - bacteria. The main goal of these industries is the transformation of the substrate (nutrient medium) under the action of microbial enzymes into the necessary products. In other industries, for example in the production of baker's yeast, the main task is to accumulate the maximum amount of cultivated yeast.
Main groups of microorganisms used in industries Food Industry, - bacteria, yeast and mold fungi.
Bacteria. They are used as activators of lactic acid, acetic, and acetone-butyl fermentation.
Cultural lactic acid bacteria are used in the production of lactic acid, in baking, and sometimes in alcohol production. They convert sugar into lactic acid according to the given equation 2CH 3 CHONCOOH.
Lactic acid bacteria are cylindrical or rod-shaped, as well as spherical, gram-positive, non-motile, non-spore-forming.
The optimal temperature for the growth of most lactic acid bacteria is 20...30 o C, like other non-spore bacteria, they die at 70...75 o C.
In the process of producing rye bread, true (homofermentative) and non-true (heterofermentative) lactic acid bacteria are involved. Heterofermentative lactic acid bacteria, along with lactic acid, produce other organic acids (mainly acetic acid), alcohol and carbon dioxide. True bacteria in rye dough are involved only in acid formation, while non-true bacteria, along with acid formation, have a significant effect on the loosening of the dough, being energetic gas formers. Lactic acid bacteria in rye dough also have a significant impact on the taste of bread, since it depends on the total amount of acids contained in the bread and on their ratio. In addition, lactic acid affects the formation process and structural and mechanical properties of rye bread.
In the alcohol industry, lactic acid fermentation can be used to acidify yeast wort. Wild lactic acid bacteria adversely affect the technological processes of fermentation production and deteriorate the quality of the finished product. Lactic acid, which is formed during lactic acid fermentation, stimulates the development of yeast and suppresses the vital activity of foreign microorganisms.
Butyric acid fermentation caused by butyric acid bacteria are used to produce butyric acid, the esters of which are used as aromatic substances, and these bacteria are dangerous for alcohol production, since butyric acid inhibits the development of yeast and inactivates a-amylase.
Butyric acid bacteria are strict anaerobes, having large spore-forming balls up to 10 microns in length. Along with butyric acid, they can form acetic, lactic, caproic, caprylic and other acids, as well as ethyl and butyl alcohols in smaller quantities. The optimal temperature for bacterial growth is 30...40 o C; at a pH below 4.9 they do not develop.
Special types of butyric acid bacteria include acetone-butyl bacteria, which convert starch and other carbohydrates into acetone, butyl and ethyl alcohols. These bacteria are used as fermentation agents in acetone-butyl production.
Acetic acid bacteria are gram-negative, rod-shaped, non-spore-bearing, strictly aerobic organisms that develop under the same conditions as yeast. They are used to produce vinegar (acetic acid solution), since they are capable of oxidizing ethyl alcohol into acetic acid according to the equation:
CH 3 CH 2 OH + O 2 = CH 3 COOH + H 2 O + 487 kJ
It should be noted that acetic acid fermentation is harmful for alcohol production, as it leads to a decrease in alcohol yield, and in brewing it worsens the quality of beer and causes its spoilage.
Putrefactive bacteria – cause the breakdown of proteins. Under aerobic conditions, complete mineralization of protein occurs down to carbon dioxide, ammonia, hydrogen sulfide, water and minerals. Putrefactive bacteria cause especially great harm to yeast, reducing their shelf life. Nitrites at a concentration of even 0.0005% inhibit the proliferation of yeast.
Yeast. They are widely used as fermentation agents in the production of alcohol and beer, in winemaking, in the production of bread kvass, and also in bakery for loosening dough.
For food production, yeasts are important - Saccharomyces, which form spores, and imperfect yeast - non-Saccharomycetes (yeast-like fungi), which do not form spores. The Saccharomyces family is divided into several genera. The most important of this family is the genus Saccharomyces (Saccharomycetes). The genus is divided into species, and the remaining individual varieties of the species, differing in some characteristics, are called races. Each industry uses specific yeast races. There are dusty and flocculated yeasts. In the former, throughout the entire period of life, the cells are isolated from each other, while in the latter, the cells stick together, forming flakes, and quickly settle.
Cultivated yeast belongs to the Saccharomyces family S. cerevisiae. The optimum temperature for yeast propagation is in the range of 25-30 o C, and the minimum temperature is about 2-3 o C. At 40 o C, growth stops, the yeast dies off, but the yeast tolerates low temperatures well, although its reproduction stops.
There are top-fermenting and bottom-fermenting yeasts. Within each of these groups there are several distinct races.
Top-fermenting yeast in the top-fermentation stage is released on the surface of the fermentation medium in the form of a rather thick layer of foam and remains in this state until the end of fermentation. In the meantime, they settle, but do not give a dense sediment. These yeasts are dusty yeasts and do not stick together, unlike bottom-fermenting flocculated yeasts, the shells of which are sticky, which leads to cell sticking and rapid sedimentation.
Of the cultivated yeasts, bottom-fermenting yeasts include most wine and beer yeasts, and top-fermenting yeasts include alcoholic, bakery and some races of brewer's yeasts. Initially, only top-fermenting yeasts were known, since the fermentation of various juices occurred at ordinary temperatures. Wanting to get drinks saturated with CO 2, people began to ferment at low temperatures. Under the influence of changed external conditions, bottom-fermenting yeast was developed, which is widely used in industry.
As noted earlier, in the process of alcoholic fermentation, two main products are formed from glucose - ethyl alcohol and carbon dioxide, as well as intermediate secondary products: glycerin, succinic, acetic, citric and pyruvic acids, acetaldehyde, 2,3-butylene glycol, acetoin, esters and so-called fusel oils (isoamyl, isotopropyl, butyl and other alcohols).
Fermentation of individual sugars occurs in a certain sequence, determined by the rate of their diffusion into the yeast cell. Glucose and fructose are the fastest fermented by yeast. However, sucrose, as such, disappears (inverts) in the medium at the beginning of fermentation under the action of the enzyme contained in the yeast cell wall - B-fructofuranosidase, with the formation of glucose and fructose, which are easily used by the cell. When there is almost no fructose and glucose left in the medium, the yeast consumes maltose.
Yeast has the ability to ferment very high concentrations of sugar - up to 60%. They also tolerate high concentrations of alcohol - up to 14-16 vol. %. The toxic effect of alcohol increases with increasing temperature.
In the presence of oxygen, alcoholic fermentation stops and the yeast receives energy through oxygen respiration:
C 6 H 12 O 6 + 6O 2 CO 2 + 6H 2O + 2824 kJ
Since this process is more energetically rich than the fermentation process (118 kJ), the yeast spends sugar much more economically. The cessation of fermentation under the influence of atmospheric oxygen is called Pasteur effect.
In alcohol production, the yeast species S. cerevisiae is used, which has the highest fermentation energy, produces maximum alcohol and ferments mono- and disaccharides, as well as some dextrins.
In baker's yeast, quickly multiplying races with good lifting power and storage stability are valued. Lifting force is determined both by the characteristics of the yeast races and by the method of production.
In brewing, bottom-fermenting yeast is used, adapted to relatively low temperatures. Brewer's yeast must be microbiologically pure, and also have the ability to form flocs, quickly settle to the bottom of the fermentation apparatus and produce a clear drink with a certain taste and aroma.
In winemaking, yeast is valued because it multiplies quickly, has the ability to suppress other types of yeast and microorganisms and give the wine an appropriate bouquet. Yeast used in winemaking belongs to the S/ vini species, vigorously fermenting glucose, fructose, sucrose and maltose. Most wine yeasts are low-fermenting yeasts. In winemaking, almost all production yeast cultures are isolated from young wines in various areas.
In the brewing industry, grassroots yeast of the S/ carlsbergensis species (mainly flocculent races) is used. The fermentation caused by them proceeds well at temperatures from 6 to 8 o C.
Yeasts of the non-saccharomycetes family are produced as valuable feed for farm animals.
In industries such as brewing and yeast production, yeast-like fungi are production pests.
Zygomycetes. Previously, zygomycetes were called molds. They are playing big role as enzyme producers. Fungi of the genus Aspergillus produce amylolytic, proteolytic, pectolytic and other enzymes, which are used in the alcohol industry instead of malt for the saccharification of starch, in the brewing industry when partially replacing malt with unmalted grain, etc.
In the production of citric acid, A. Niger is the causative agent of citric acid fermentation, converting sugar into citric acid.
However, in some cases, molds cause spoilage food products.
Microorganisms are widely used in the food industry, households, and the microbiological industry to produce amino acids, enzymes, organic acids, vitamins, etc. Classic microbiological production includes winemaking, brewing, making bread, lactic acid products and food vinegar. For example, winemaking, brewing and the production of yeast dough are impossible without the use of yeast, which is widespread in nature.
The history of industrial production of yeast began in Holland, where the first factory producing yeast was founded in 1870. The main type of product was compressed yeast with a moisture content of about 70%, which could be stored for only a few weeks. Long-term storage was impossible, since the pressed yeast cells remained alive and retained their activity, which led to their autolysis and death. One of the methods for industrially preserving yeast is drying. In dry yeast, at low humidity, the yeast cell is in an anabiotic state and can be preserved long time. The first dry yeast appeared in 1945. In 1972, the second generation of dry yeast, the so-called instant yeast, appeared. Since the mid-1990s, a third generation of dry yeast has emerged: baker's yeast Saccharomyces cerevisiae, which combine the benefits of instant yeast with a highly concentrated complex of specialized baking enzymes in one product. This yeast not only improves the quality of bread, but also actively resists the process of staling.
Baker's yeast Saccharomyces cerevisiae are also used in the production of ethyl alcohol.
Winemaking uses many different races of yeast to produce a unique brand of wine with unique qualities.
Lactic acid bacteria are involved in the preparation of foods such as sauerkraut, pickles, pickled olives and many other pickled foods.
Lactic acid bacteria convert sugar into lactic acid, which protects food products from putrefactive bacteria.
With the help of lactic acid bacteria, a wide range of lactic acid products, cottage cheese, and cheese are prepared.
However, many microorganisms play a negative role in human life, being pathogens of diseases in humans, animals and plants; they can cause food spoilage, destruction of various materials, etc.
To combat such microorganisms, antibiotics were discovered - penicillin, streptomycin, gramicidin, etc., which are metabolic products of fungi, bacteria and actinomycetes.
Microorganisms provide humans with the necessary enzymes. Thus, amylase is used in the food, textile, and paper industries. Protease causes the breakdown of proteins in various materials. In the East, protease from mushrooms was used several centuries ago to make soy sauce. Currently, it is used in the production of detergents. When canning fruit juices, an enzyme such as pectinase is used.
Microorganisms are used for cleaning Wastewater, processing waste from the food industry. During anaerobic decomposition organic matter waste produces biogas.
IN last years new productions have appeared. Carotenoids and steroids are obtained from mushrooms.
Bacteria synthesize many amino acids, nucleotides and other reagents for biochemical research.
Microbiology is a rapidly developing science, the achievements of which are largely related to the development of physics, chemistry, biochemistry, molecular biology, etc.
To successfully study microbiology, knowledge of the listed sciences is required.
This course focuses primarily on food microbiology. Many microorganisms live on the surface of the body, in the intestines of humans and animals, on plants, on food products and on all objects around us. Microorganisms consume a wide variety of foods and adapt extremely easily to changing living conditions: heat, cold, lack of moisture, etc. They multiply very quickly. Without knowledge of microbiology, it is impossible to competently and effectively manage biotechnological processes, maintain high quality food products at all stages of its production and prevent the consumption of products containing pathogens of foodborne illnesses and poisoning.
It should be especially emphasized that microbiological studies of food products, not only from the point of view technological features, but also, no less important, from the point of view of their sanitary and microbiological safety, they are the most complex object of sanitary microbiology. This is explained not only by the diversity and abundance of microflora in food products, but also by the use of microorganisms in the production of many of them.
In this regard, in microbiological analysis of food quality and safety, two groups of microorganisms should be distinguished:
– specific microflora;
– nonspecific microflora.
Specific– these are cultural races of microorganisms that are used to prepare a particular product and are an essential link in the technology of its production.
This microflora is used in the technology of producing wine, beer, bread, and all fermented milk products.
Nonspecific are microorganisms that enter food products from environment, polluting them. Among this group of microorganisms, saprophytic, pathogenic and opportunistic microorganisms are distinguished, as well as microorganisms that cause food spoilage.
The degree of contamination depends on many factors, which include the correct procurement of raw materials, their storage and processing, compliance with technological and sanitary regimes for the production of products, their storage and transportation.
Due to the wide variety of enzymes they synthesize, microorganisms can perform many chemical processes more efficiently and economically than if these processes were carried out chemical methods. The study of the biochemical activity of microorganisms made it possible to select conditions for their maximum activity as producers of various useful enzymes - pathogens of necessary chemical reactions and processes. Microorganisms are increasingly used in various branches of the chemical and food industries, agriculture, and medicine.
In our country, a new industry has been created and is successfully developing - microbiological, all production of which is based on the activity of microorganisms.
Microorganisms with the help of which food products are produced are called cultural. They are obtained from pure cultures that are isolated from individual cells. The latter are stored in museum collections and supplied to various industries.
As a result of chemical reactions carried out by cultural microorganisms, plant or animal raw materials are transformed into food products. Many vital food products are obtained with the help of microorganisms, and although their production has been familiar to man since ancient times, the role of microorganisms in it has been discovered relatively recently.
Bakery production.
Bread baking is based on the activity of yeast and lactic acid bacteria developing in the dough. The combined action of these microorganisms leads to the fermentation of flour sugars. Yeast causes alcoholic fermentation, and lactic acid bacteria cause lactic acid fermentation. The resulting lactic and other acids acidify the dough, maintaining an optimal pH level for yeast activity. Carbon dioxide loosens the dough and accelerates its ripening.
The use of cultural microorganisms in the form of pressed baker's yeast, dried or liquid starters improves the taste and aroma of bread.
Cheese production.
Cheese making is based on the activity of many types of microorganisms: lactic acid bacteria (thermophilic streptococcus), propionic acid bacteria, etc. Under the influence of lactic acid bacteria, lactic acid accumulates and milk is fermented; under the influence of other beneficial microorganisms, cheese ripens. Some molds are also involved in this process. Rennet and lactic acid bacteria produce deep breakdown of proteins, sugar and fat. Various bacteria cause the accumulation of volatile acids in sharp cheeses, giving them a specific aroma.
Production of fermented milk products.
Cottage cheese, sour cream, butter, acidophilus, yogurt are prepared using pure cultures using various starters. The milk is pre-pasteurized. Mesophilic lactic acid bacteria are used to produce cottage cheese and sour cream; fermented baked milk, Varenets and similar products - thermophilic streptococci and Bulgarian bacillus; acidophilus - acid-tolerant lactic acid bacteria; kefir - multicomponent starter cultures consisting of yeast, lactic acid and often acetic acid bacteria. To make cultured butter, a starter of lactic acid bacteria is introduced into pasteurized cream and kept until the required acidity.
Brewing, alcohol, distillery and wine production.
Wine, beer, kvass, vodka and other drinks are prepared using yeast, which causes alcoholic fermentation of sugar-containing liquids. As a result of fermentation of liquid (wort, mash, juice, etc.), alcohol, CO 2 and small amounts of by-products are formed. Lactic acid bacteria play a supporting role: they acidify the environment and facilitate the activity of yeast (for example, in the production of kvass). In the production of alcohol and beer, enzyme preparations of fungal and bacterial origin are also used to saccharify mashes.
Pickling and salting.
The essence of this method of preservation is to create conditions for the preferential development of some microorganisms - lactic acid bacteria - and suppress the development of others - putrefactive bacteria. Cabbage, cucumbers, tomatoes, apples, and watermelons are fermented. This method is also used when storing livestock feed for long-term storage - green mass from herbs, plant residues, etc. is fermented. This process is called feed ensiling.
Preparation of organic acids.
Acetic, lactic and citric acids are also produced with the help of microorganisms. Lactic acid is produced by fermentation from sugar-containing raw materials - molasses, starch, whey, etc.
Lactic acid bacteria are grown on media containing up to 15% sugar. The yield of lactic acid reaches 60-70% of the mass of sugar contained in the mash.
Industrial production Vinegar for food purposes is based on acetic acid fermentation. Acetic acid bacteria in special vats on beech shavings oxidize the incoming nutrient medium- acetic-alcohol solution - to acetic acid.
Citric acid was previously obtained from citrus fruits. Currently, it is also obtained by fermentation. The causative agent of fermentation is the fungus Aspergillus niger, the main raw material is black molasses. Fermentation occurs in a solution containing 15% sugar under aerobic conditions at a temperature of about 30 °C. Citric acid is used in the confectionery industry, production of soft drinks, syrups, cooking and medicine.
Of the more than 100 thousand known microorganisms, only a few hundred species are used in industry, since the industrial strain must meet a number of strict requirements:
1) grow on cheap substrates;
2) have a high growth rate or give a high yield of product in a short time;
3) exhibit synthetic activity towards the desired product; the formation of by-products should be low;
4) be stable in terms of productivity and the requirements of cultivation conditions;
5) be resistant to phage and other types of infections;
6) be harmless to people and the environment;
7) thermophilic, acidophilic (or alkophilic) strains are desirable, since it is easier to maintain sterility in production with them;
8) anaerobic strains are of interest, since aerobic strains create difficulties during cultivation - they require aeration;
9) the product generated must have economic value and be easily distinguished.
In practice, strains of four groups of microorganisms are used:
- yeast;
– filamentous fungi (molds);
– bacteria;
– ascomycetes.
The term "yeast" in the strict sense does not have a taxonomic meaning. These are unicellular eukaryotes belonging to three classes: Ascomycetes, Basidiomycetes, Deuteromycetes.
Ascomycetes include, first of all, Saccharomyces cerevisiae, certain strains of which are used in brewing, winemaking, and the production of bread and ethyl alcohol.
The ascomycetes Saccharomyces lipolytica degrade oil hydrocarbons and are used to obtain protein mass.
The deuteromycete Candida utilis is used as a source of protein and vitamins and is grown on non-food raw materials: sulfite liquors, wood hydrolysates and liquid hydrocarbons.
The deuteromycete Trichosporon cutaneum oxidizes many organic compounds, including toxic ones (for example, phenol), and is used in wastewater treatment.
Filamentous fungi use:
– in the production of organic acids: citric (Aspergillus niger), gluconic (Aspergillus niger), itaconic (Aspergillus terreus), furmaric (Rhizopus chrysogenum);
– in obtaining antibiotics (penicillin and cephalosporin);
– in the production of special types of cheeses: Camembert (Penicillium camamberti), Roquefort (Penicillium roqueforti);
– cause hydrolysis in solid media: in rice starch when producing sake, in soybeans when producing tempeh, miso.
Beneficial bacteria are classified as eubacteria.
Lactic acid bacteria of the genera Lactobacillus, Leuconostoc, and Lactococcus have been used industrially for a long time.
Acetic acid bacteria of the genera Acetobater and Gluconobacter convert ethanol into acetic acid.
Bacteria of the genus Bacillus are used to produce toxins harmful to insects, as well as for the synthesis of antibiotics and amino acids.
Bacteria of the genus Corynebacterium are used to produce amino acids.
Of the actinomycetes, the most representative are the genera Streptomyces and Micromonospora, used as producers of antibiotics. When growing on solid media, actinomycetes form thin mycelium with aerial hyphae, which differentiate into chains of conidiospores.
Currently, the following compounds are synthesized using microorganisms:
– alkaloids,
– amino acids,
– antibiotics,
– antimetabolites,
– antioxidants,
– proteins,
– vitamins,
– herbicides,
– enzyme inhibitors,
– insecticides,
– ionophores,
– coenzymes,
– lipids,
- nucleic acids,
– nucleotides and nucleosides,
– oxidizing agents,
– pigments,
– surfactants,
– polysaccharides,
– antihelminthic agents,
– antitumor agents,
– solvents,
– plant growth hormones,
– sugar,
– sterols and converted substances,
– iron transport factors,
– pharmacological substances,
– enzymes,
– emulsifiers.
2 PRODUCTION OF SINGLE CELL PROTEINS
ORGANISMS
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2.1 The feasibility of using microorganisms for
protein production
In accordance with nutritional standards, a person should receive from 60 to 120 g of complete protein with food every day.
To maintain the vital functions of the body, build cells and tissues, constant synthesis of various protein compounds is necessary. If plants and most microorganisms are able to synthesize all amino acids from carbon dioxide, water, ammonia and mineral salts, then humans and animals cannot synthesize some amino acids (valine, leucine, isoleucine, lysine, methionine, threonine, tryptophan and phenylalanine). These amino acids are called essential. They must come from food. Their deficiency causes severe human diseases and reduces the productivity of farm animals.
Currently, the global protein deficit is about 15 million tons. Microbiological synthesis is the most promising. If for cattle it takes 2 months to double the protein mass, for pigs - 1.5 months, for chickens - 1 month, then for bacteria and yeast - from 1 to 6 hours. World production of food protein products due to microbial synthesis is more than 15 thousand tons per year.
Let's consider an example: the doubling time of E. coli is 20 minutes, then after 20 minutes two daughter cells are formed from one cell, after 40 minutes - four “granddaughters”, after 60 minutes - eight “great-granddaughters”, after 80 minutes - 16 “great-great-granddaughters”. After 10 hours 40 minutes, over 6 billion bacteria will be formed from one bacterium, which corresponds to the population of the Earth, and after 44 hours, from one bacterium weighing 1 10 -12 g, biomass will be formed in the amount of 6 10 24 g, which corresponds to the mass of the Earth.
The use of various microorganisms as sources of protein and vitamins is due to the following factors:
A) the possibility of using various chemical compounds, including industrial wastes, for cultivating microorganisms;
B) relatively simple technology for the production of microorganisms, which can be carried out year-round; the possibility of its automation;
C) high content of protein (up to 60...70%) and vitamins, as well as carbohydrates, lipids in microbial preparations;
D) increased content of essential amino acids compared to plant proteins;
D) the possibility of directed genetic influence on chemical composition microorganisms in order to improve the protein and vitamin value of the product.
The industrial production of food products based on microorganisms requires thorough biomedical research. Such products must undergo comprehensive testing to identify carcinogenic, mutagenic, embryotropic effects on humans and animals. Toxicological studies, digestibility of microbial synthesis products are the main criteria for the feasibility of their production technology.
Yeast, bacteria, algae and filamentous fungi are used to produce proteins.
The advantage of yeast over other microorganisms is their manufacturability: resistance to infections, ease of separation from the environment due to the large size of the cells. They are able to accumulate up to 60% of protein, rich in lysine, threonine, valine and leucine (these amino acids are scarce in plant foods). Mass fraction nucleic acids up to 10%, which has a harmful effect on the body. As a result of their hydrolysis, many purine bases are formed, which are then converted into uric acid and its salts, which cause urolithiasis, osteochondrosis and other diseases. The optimal rate of adding yeast mass to the feed of farm animals is from 5 to 10% of dry matter. Yeast is used for food and feed purposes.
The advantages of bacteria are their high growth rate and the ability to synthesize up to 80% of protein. The resulting protein contains many deficient amino acids: methionine and cysteine. The disadvantages are the small size of the cells and their low concentration in the culture medium, which complicates the isolation process. Some bacterial lipids may contain toxins. Mass fraction of nucleic acids up to 16%. Used for feed purposes only.
The advantages of algae are the high content of protein with complete amino acid composition, which accumulates in an amount of 65%, easy isolation of algae from the culture medium, low content of nucleic acids - 4% (for comparison - in higher plants 1...2%). Algae are used for food and feed purposes.
Filamentous fungi are traditionally used as a food product in African countries, India, Indonesia, China, etc. They accumulate up to 50% protein, the amino acid composition of which is close to protein of animal origin, and are rich in B vitamins. The cell walls are thin and easily digested in the gastrointestinal tract. intestinal tract of animals. The mass fraction of nucleic acids is 2.5%.
Since 1985, microbial protein has been used in the food industry for the manufacture of various products and semi-finished products.
There are three main forms of microbial protein use considered in food production:
1) whole mass (without destruction of cell walls);
2) partially purified biomass (destruction of cell walls and removal of undesirable components is provided);
3) proteins isolated from biomass (isolates).
The WHO (World Health Organization) concluded that the protein of microorganisms can be used in food, but the permissible amount of nucleic acids introduced along with the protein into the diet of an adult should not exceed 2 g per day. The introduction of microbial protein does not cause negative consequences, but allergic reactions, gastric diseases, etc. occur.
In the previous sections you have already become acquainted with some techniques for working with microorganisms and had the opportunity to try these techniques out. As biotechnologists move from the laboratory to the industrial scale, they must solve a variety of problems across a variety of disciplines, including bioengineering, chemistry, and biology. When making decisions in the industrial production of bacteria, it is important to consider both economic, social and ethical aspects. In this section we will touch on some of the practical aspects of large-scale production, and in subsequent sections we will look at specific examples microbiological production and related problems.
Use of microorganisms in industrial production it is possible for the following reasons:
1) microorganisms have simple nutritional needs;
2) in fermenters (large vessels in which microorganisms grow), growth conditions can be very precisely controlled;
3) microorganisms have high growth rates;
4) reactions can be carried out at lower temperatures than in conventional chemical plants; Energy bills are reduced accordingly;
5) microorganisms provide higher product yield and higher specificity than conventional chemical production;
6) a wide range of chemical compounds can be used and produced;
7) it is possible to produce some complex chemical compounds, such as hormones and antibiotics, which are difficult to obtain by other methods, as well as specific isomers (such as L-amino acids);
8) the genetics of microorganisms is relatively simple, and methods for genetic manipulation of them are constantly evolving.
However, the need to use special methods, such like sterilization methods and complex separation methods may entail a significant increase in process technical requirements.
Screening
We know what for microorganisms characterized by a huge variety of chemical reactions that they can carry out and the products that they form. However, only a small part of their potential is used in industrial production. Commercial companies, especially drug manufacturers, are constantly searching for microorganisms that may be useful. In hopes of discovering new commercially important products or more effective ways To obtain available products, microorganisms are collected and cultivated from all over the world, from a wide variety of habitats. Very often this is purely empirical work in the sense that significant role In any discovery, chance plays a role. Testing microorganisms in this way is called screening. Good example is a continuous screening carried out to discover new antibiotics. The first antibiotic was discovered in 1928 by Alexander Fleming and named penicillin after the name of the fungus Replicum that produces it. Natural antibiotics are chemical substances, synthesized by microorganisms and killing other microorganisms or inhibiting their growth. Since 1928, more than 5,000 different antibiotics have been isolated from microorganisms, including a number of different penicillins that vary slightly in structure and activity. Most of the antibiotics discovered are unsuitable for medical purposes, mainly due to their high toxicity. However, members of the genus Streptomyces have proven to be an extremely rich source of various antibiotics, including streptomycin.
Antibiotics used to treat bacterial or fungal diseases in humans and domestic animals. Some of them also suppress the growth of cancerous tumors. Apparently, antibiotics are products of secondary metabolism. With systematic screening, there is always the hope of finding a new “wonder drug” or microorganism that produces a known antibiotic, but with improved properties.