Introduction to Microbiology Class 10 Science Notes Maharashtra State Board
Applied Microbiology
The branch of biology in which the study of the enzymes related to some prokaryotes and eukaryotic microbes, proteins, applied genetics, molecular biology, etc. is performed is called applied microbiology. This study is used for society and various products like food and medicines are produced on a large scale with the help of microorganisms.
Industrial Microbiology
This science is related to the commercial use of microbes in which various economic, social, and environment-related processes and products are included. Various microbial processes useful for this purpose are carried out.
Industrial Microbiology: Main Features
- Various productions with the help of the fermentation process. Ex. Bread, cheese, wine, raw material for chemicals, enzymes, nutrients, medicines, etc.
- Use of microbes for garbage management and pollution control.
Products
1. Dairy Products
Since ancient days, milk has been converted into various products for preservation purposes. Ex. Cheese, butter, cream, kefir, yogurt, etc. Water content and acidity of the milk change during the formation of these products and texture, taste, and flavor are improved. These processes are performed on a large scale with more skill. For the production of most milk products, bacteria in the milk itself are used; only cheese is produced with the help of fungi. The basic process for the production of yogurt, cheese, and cream is the same. Milk is pasteurized at the beginning to destroy unwanted microbes. It is then fermented with the help of lactobacilli. In this process, the lactose sugar of the milk is converted into lactic acid, and milk proteins are coagulated with the help of lactic acid. Besides, compounds with taste and flavor are also formed. Ex. Diacetyl has the flavor of butter.
2. Yoghurt Products
Yogurt is a milk product produced with the help of lactobacilli (inoculant). To maintain the protein content, condensed milk powder is mixed with milk to be fermented for the industrial production of yogurt. Milk is boiled and once it cools to a warm temperature, bacterial strains of Streptococcus thermophilus and Lactobacillus delbrueckii are added to it in 1 : 1 proportion. Lactic acid is formed due to Streptococcus which makes the proteins gel out giving a dense consistency to the yoghurt. Acetaldehyde-like compounds are formed due to lactobacilli that give a characteristic taste to the yogurt. Nowadays, various fruit juices are mixed with yogurt to impart different flavors. Ex. Strawberry yogurt, banana yogurt, etc. The shelf life of yogurt and its probiotic properties can be improved by pasteurization.
3. Butter
Two types of butter sweet cream and cultured are produced on a large scale. Microbes are used for the production of cultured variety.
4. Cheese Production
Cheese is produced on a large scale from the abundantly available cow milk all over the world. First, chemical and microbiological tests of milk are performed. Some colors and microbes like Lactobacillus lactis, Lactobacillus cremoris, and Streptococcus thermophilus are mixed with milk. It imparts sourness to the milk. After this, to impart the dense texture, whey (water in yogurt) needs to be removed. An enzyme, rennet obtained from the alimentary canal of cattle was traditionally used earlier. However, an enzyme protease obtained from fungi is used at present to produce vegetarian cheese. The whey is separated from yogurt (which has some other uses). Then, the process of production of cheese is started through steps like cutting the solid yogurt into pieces, washing, rubbing, salting, and mixing essential microbes, pigments, and flavors. Then, the cheese is pressed cut into pieces, and stored for ripening.
During the industrial production of milk products, strict cleanliness and sterilization are essential as bacteria can be attacked by viruses. Hence, virus-resistant varieties of bacteria are developed. Recently, the use of mutant varieties of bacteria has been increased. Artificially, some strains are developed that will help to avoid unnecessary steps/materials. Freshly prepared cheese is always soft e.g. cottage cheese, cream cheese, mozzarella cheese. On storing for 3 to 12 months, semi-hard cheddar cheese is formed whereas after ripening for 12 – 18 months, very hard cheese called parmesan cheese is formed.
Probiotics
These are also milk products but contain active bacteria e.g. Lactobacillus, Acidophilus, Lactobacillus casei, Bifidobacterium bifidum, etc. These microbes maintain the balance of intestinal microorganisms i.e. increase the population of microbes helping the digestion and decrease the population of harmful microbes (ex. Clostridium). Probiotic products are available in various forms like yogurt, kefir, sauerkraut (pickle of cabbage), dark chocolate, miso soup, pickles, oils, corn syrup, artificial sweeteners, microalgae (Seafood like Spirulina, Chlorella, Blue-green algae, etc.).
Why the probiotics have developed much importance in recent days? These products form the colonies of useful microbes in the alimentary canal and control other microbes and their metabolic activities, improve resistance, and lower the ill effects of harmful substances formed during metabolic activities. Useful microbes become inactive due to antibiotics; probiotics make them active again. Nowadays, probiotics are used for the treatment of diarrhea and treatment of poultry.
Bread
Different types of breads are produced from flour or cereals. The dough is formed by mixing baker’s yeast – Saccharomyces cerevisiae, water, salt, and other necessary materials with flour. Due to the fermentation of carbohydrates by yeast, sugar is converted into dioxide (CO2) and ethanol. The dough rises due to CO2 and the bread becomes spongy. Compressed yeast is used in the commercial bakery industry. It is available in dry, granular form for domestic use. The yeast produced for commercial use contains various useful contents like carbohydrates, fats, proteins, various vitamins, and minerals. Due to this, bread and other products produced with the help of yeast become nutritive. Ingredients like vinegar, soya sauce, and monosodium glutamate (ajinomoto) that are used in presently popular Chinese food are produced by microbial fermentation.
Vinegar Production
Vinegar is used in each country of the world to impart a sour taste to food materials and for the preservation of pickles, sauce, ketchup, chutneys, etc. Chemically, vinegar is 4% acetic acid (CH3COOH). Ethanol, an alcohol is obtained by fermentation of carbon compounds like fruit juices, maple syrup, sugar molasses, and starch of the roots; with the help of yeast Saccharomyces cerevisiae.
A mixture of bacterial strains like Acetobacter and Glucanobacter is mixed with ethanol for microbial degradation. Acetic acid and other by-products are obtained through it. Acetic acid is separated from the mixture by rarefaction. Acetic acid is bleached with the help of potassium ferrocyanide. Then, it is pasteurized. Finally, a very small quantity of SO2 gas is mixed to produce vinegar. Soya sauce is produced by fermentation of the mixture of flour of wheat or rice and soybean with the help of the fungus Aspergillus oryzae.
Production of Beverages
| Fruit | Microbe Used | Role of Microbe | Name of Beverage |
| 1. Caffea arabica | Lactobacillus brevis | Separating seeds from fruit | Coffee |
| 2. Theobroma cacao | Candida, Hansenula, Pichia, Saccharomyces. | Separating seeds from fruit | Cocoa |
| 3. Grapes | Saccharomyces cerevisiae | Fermentation of juice | Wine |
| 4. Apple | Saccharomyces cerevisiae | Fermentation of juice | Cider |
Microbial Enzymes
Nowadays, instead of chemical catalysts, microbial enzymes are used in the chemical industry. These enzymes are active at low temperatures, pH, and pressure; due to which energy is saved, and erosion-proof instruments are also not necessary. Enzymes carry out specific processes; hence unnecessary byproducts are not formed due to which expenses on purification are minimized. In the case of microbial enzymatic reactions, elimination and decomposition of waste material is avoided and enzymes can be reused. Hence, such enzymes are eco-friendly. Some examples of microbial enzymes are oxidoreductases, transferases, hydrolases, lyases, isomerases, ligases, etc. The process of dirt/muck removal occurs at low temperatures too due to the mixing of enzymes with detergents. Glucose and fructose syrup can be obtained from corn flour by the action of enzymes obtained from bacilli and streptomyces. Microbial enzymes are used in various industries like cheese, plant extracts, textiles, leather, paper, etc.
Organic acids used in various commercial products and microbes useful for the same
| Source | Microbe | Amino Acid | Use |
| Sugar and beet molasses, ammonia salt | Brevibacterium, Corynebacterium | L-glutamic acid | Production of monosodium glutamate (Ajinomoto) |
| Sugar molasses, salt | Aspergillus niger | Citric acid | Drinks, toffees, chocolate production |
| Glucose, corn steep liquor | Aspergillus niger | Gluconic acid | Production of minerals used as supplements for calcium and iron |
| Molasses, corn steep liquor | Lactobacillus delbrueckii | Lactic acid | Source of nitrogen, production of vitamins |
| Molasses, corn steep liquor | Aspergillus itaconius | Itaconic acid | Paper, textile, plastic industry, gum production |
What is the xanthan gum that imparts thickness to your favorite ice creams, puddings, chocolates, milkshakes, chocolate drinks, instant soups, etc.? This gum is obtained by fermentation of starch and molasses with the help of Xanthomonas species. It is variously useful due to properties like solubility in hot and cold water, high density, etc. It is used for the production of pigments, fertilizers, weedicides, textile pigments, toothpaste, high-quality paper, etc.
Substances obtained by microbial processing and their roles
| Substances Obtained by Microbial Processing | Roles |
| Citirc, Malic and Lactic acid | To impart acidity |
| Glutamic acid, Lysine, Tryptophan | Protein binding |
| Nycin and natamycin | Microbial restrictor |
| Ascorbic acid (Vit. C), B12, B2 | Antioxidants, vitamins. |
| Beta carotene, lycopene, xanthenes, lutein | Edible colours |
| Polysaccharides, glycolipids | Emulsifiers |
| Vanillin, Ethyl butyrate (fruit flavor), peppermint flavor, the essence of various fruits and flowers | Essence |
| Xylitol, aspartame | Artificial sweetener (low calorie) |
Antibiotics
Many diseases of humans and other animals have been controlled due to antibiotics obtained from different types of bacteria and fungi. Antibiotics like penicillin, cephalosporins, monobactam, bacitracin, erythromycin, gentamycin, neomycin, streptomycin, tetracycline, vancomycin, etc. are used against various strains of gram-positive and gram-negative bacteria. Rifamycin is effective against tuberculosis.
Microbes and Fuels
- Gaseous fuel – methane can be obtained by microbial anaerobic decomposition of urban agricultural and industrial waste.
- Ethanol, an alcohol is a clean (smokeless) fuel obtained during fermentation of molasses by the yeastSaccharomyces.
- Hydrogen gas is considered to be the fuel of the future. Hydrogen gas is released during bio-photolysis of water in which bacteria perform the photoreduction.
Similar to fuels, various industrial chemicals are also produced through microbial processes. Ex. various alcohols, acetone, organic acids, fatty acids, and polysaccharides, that are useful as raw materials in the chemical industry. Some of these are useful as raw materials for plastic and food products.
Bio-fuel:
Biofuel is an important renewable source of good energy. These fuels are available in solid (coal, dung, crop residue), liquid (vegetable oils, alcohol), and gaseous (gobar gas, coal gas) forms. These fuels are easily available and in plenty of quantity. These are reliable fuels of the future.
Microbial Pollution Control
Solid wastes, sewage, and various pollutants are ever-increasing with the increase in pollution. Along with it, ever-increasing diseases and the degradation of the environment are worldwide problems. Especially, cities in densely populated countries like India are affected by these problems. Life of future generations will be difficult if these problems are not solved at the right time and to the right extent. Let us see the role of microbes in the environment. You already know that microbes are used for the disposal of solid waste through biogas plants and compost production. How urban waste that is accumulated in terms of tonnes, be disposed of?
Land-filling Sites
Degradable waste being accumulated in urban areas is used for this purpose. Large pits are dug in open spaces far away from the residential area and those pits are lined with plastic sheets as a precaution against pollution of soil due to leaching of toxic and harmful materials.
Compressed waste is dumped in the pit. It is covered with layers of soil, sawdust, leafy waste, and specific biochemicals. Bioreactors are mixed in some places. Microbes present in soil and other top layers decompose the waste. The filled pit is sealed with soil slurry. Best-quality compost is formed after a few days. Such landfilling sites can be reused after the removal of compost.
Sewage Management
In villages, domestic sewage is disposed of either in nearby soil or in biogas plants. However, in cities, sewage needs to be carried to a processing unit and acted upon by microbial processes. Microbes which can decompose any compound as well as destroy the pathogens of cholera, typhoid, etc. are mixed with sewage. They release methane and CO2 by decomposition of the carbon compounds present in sewage. Phenol-oxidizing bacteria decompose the xenobiotic chemicals present in sewage. The sludge that settles down in this process can again be used as fertilizer. Water released after microbial treatment is environmentally safe. Microbes are used for bioremediation of the environment polluted due to sewage.
Clean Technology
Human beings have made very fast progress in technology. However, environmental pollution is also increasing at the same speed. Let us see the ways to control air, soil, and water pollution with the help of microbes. Microbes have a natural ability to decompose manmade chemicals. Hydrocarbons and other chemicals are transformed with the help of these abilities.
- Some microbes remove the sulfur from fuels.
- Metals like copper, iron, uranium, zinc, etc. leach into the environment from low-quality metalloids. These are converted into compounds before leaching, with the help of thiobacilli and sulphobacilli.
The spilling of petroleum oil occurs in the ocean due to various reasons. This oil may prove fatal and toxic to aquatic organisms. It is not easy to remove the oil layer from the surface of water by mechanical method. However, bacteria like Pseudomonas spp. and Alcanovorax borkumensis can destroy the pyridines and other chemicals.
Hence, these bacteria are used to clear the oil spills. These are called hydrocarbonoclastic bacteria (HCB). HCB decomposes the hydrocarbons and brings about the reaction of carbon with oxygen. CO2 and water are formed in this process.
Plastic bottles are formed from the chemical substance PET (Polyethylene Terephthalate Polyester). Nowadays, most of the urban garbage consists of plastic. It has been observed that species like Vibrio, and Ideonella sakaiensis can decompose the PET. Similarly, species of fungi like Actinomycetes, Streptomyces, Nocardia, and Actinoplanes can decompose rubber from garbage.
Sulphuric acid is present in the acid rain and materials coming out of mines. You know that erosion of metals present in statues, bridges, and buildings occurs due to it. Sulphuric acid is the source of energy for some species of bacteria like Acidophillium spp. and Acidobacillus ferroxidens. Hence, these bacteria can control the soil pollution occurring due to acid rain.
Water-soluble salts of uranium are present in the wastes produced during electroplating and in effluent released in the environment from the atomic energy plant. Geobacter converts these salts of uranium into insoluble salts and thereby prevents those salts from mixing with groundwater sources.
Microbial Inoculants
Some microbes-containing inoculants are produced by the process of fermentation. These inoculants are sprayed on seeds before sowing and some of the inoculants are released into plants. Microbes in the inoculants help in plant growth by supplying nutrients. They improve the quality of vegetarian food. A solution containing Azotobacter and artificial nitrogenase is used in organic farming. Soil pollution occurring due to chemical fertilizers is prevented due to the use of these solutions. Fluoroacetamide-like chemicals are mixed with soil due to the use of chemical pesticides in agriculture. These prove to be harmful to other plants and animals as well as cause skin diseases in humans. These pesticides in the soil can be destroyed with the help of microbes.
Bioinsecticides
Bacterial and fungal toxins that can destroy pests and pathogens can be directly integrated into plants with the help of biotechnology. Being toxic to insects, they do not consume the plants. Similar to bacteria, some species of fungi and viruses are useful as pesticides. Spinosad, a byproduct of fermentation is a biopesticide
Plastic being used for storing the garbage is biodegradable polylactic acid. Such material should be used as per need only and the environment should be saved.
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