Introduction to Microbiology Science Notes
Important Points :
→ Many microbes are useful to us, such as bacteria which are used for making curds from milk, yeast used to ferment the batter of bread, bacteria used for making other milk products, bacteria and fungi used for making antibiotics. The bacteria are even used for pollution control.
→ Milk products, cheese, cocoa, pickles made from vegetables, wine and other beverages, bread, probiotic substances and cattle feed are produced with the help of microbes.
Applied Microbiology :
→ Study of the enzymes related to some prokaryotes and eukaryotic microbes, proteins, applied genetics, molecular biology, etc. comes under applied microbiology.
→ Applied microbiology is used for manufacturing various food products and medicines, using microorganisms on a large scale and hence it becomes useful for everybody.
Industrial Microbiology :
→ When microbiology is used for commercial, economic, social purpose and environment related processes, then it is called industrial microbiology. By sustained research on various microbes, various products are produced on large scale by the industrial microbiology.
The main features of industrial microbiology :
→ Using fermentation process, different products such as bread, cheese, wine and raw material for chemical reactions is produced.
→ Solid waste management and pollution control can be done with the help of microbes for garbage management and pollution control.
→ When the milk is converted into yoghurt, a small quantity of Lactobacilli culture is introduced into the warm milk. These bacteria bring about change in the constituents of the milk by fermentation and coagulation. This way yoghurt is produced.
- By preparing various milk products, one can preserve milk for a long time.
- Cheese, butter, cream, kefir, yoghurt, etc. are some important milk products.
- While making these products water content and acidity of the milk is changed. Due to this, texture, taste, aroma and flavour are improved.
- For milk products usually Lactobacilli bacteria are used. Sometimes bacteria in the milk are used for further processes.
- Cheese is produced by using fungi.
Basic process for production of milk products:
- Initial pasteurization of milk to eradicate other harmful bacteria.
- Later fermentation using Lactobacilli.
- Lactose sugar present in the milk Converted into Lactic acid.
- Lactic acid coagulates the milk proteins.
- Compounds with taste and flavour are formed, such as Diacetyl having buttery flavour.
Yoghurt production :
Method of industrial production of yoghurt :
→ Condensed milk powder mixed with milk for more proteins Milk is then boiled Cooled a little.
Streptococcus thermophilus and Lactobacillus delbrueckii bacterial strains added to it in 1 : 1 proportion.
Streptococcus Formation of lactic acid.
→ makes the proteins to gel out → Yoghurt becomes dense. Lactobacilli Formation of Acetaldehyde like compounds Give characteristic taste to yoghurt Yoghurt mixed with various fruit juices → Impart different flavours. E.g. Strawberry yoghurt, banana yoghurt Pasteurization Increases shelf life of yoghurt and its probiotic properties.
→ Butter is of two types : Sweet cream and cultured. For large scale production of cultured butter, microbes are used.
Cheese production :
Method for cheese production :
- Cheese is produced from cow milk in the entire world. Intially. chemical and microbiological tests of milk done.
- Lactobacillus lactis, Lactobacillus cremoris, and Streptococcus thermophilus + colours added to the milk.
- Milk turns sour → whey (water in yoghurt) is removed to make milk dense.
- Protease enzyme from fungi is used at present to produce vegetarian cheese.
- Previously, rennet enzyme, from alimentary canal of cattle was used.
- Whey is completely separated from yoghurt.
- To summarise, the steps of process of cheese formation: cutting the solid yoghurtinto pieces → washing → rubbing → salting → mixing of essential microbes + pigments + flavours → Cheese is pressed and cut into pieces → stored for ripening.
→ Mozzarella cheese is used for pizza. Cheddar and Swiss, Blue cheese etc. are used for burgers, Sandwich and other western foods use different types of cheese. E.g. Goat, Cheese, Camembert, Cotija, Chèvre, Feta, Emmental, Gouda, Taleggio, Parmigiano, Regginano, Manchego and Monterey, Parmesan are some of the cheese consumed world-wide especially in the Europe and America.
→ A type of cheese depends upon the milk from which it is produced. The acidity of that cheese, the colours and flavours added, the calcium content present in it are all such factors which decide the type of cheese. Some cheeses are very soft like cream cheese, while some are very hard e.g. Parmesan cheese. Thus, according to taste, flavour and the texture, the cheese become different.
→ In Probiotic food, Lactobacilli bacteria are added. This addition increases the nutritional value of the food. The harmful bacteria, Clostridium are destroyed due to probiotics. They also increase the intestinal flora of bacteria that synthesise the vitamins inside the human intestine. The disease resisting power is also increased due to probiotics.
→ Milk products containing active bacteria such as Lactobacillus acidophilus, Lactobacillus casel, Bifidobacterium bifidum, etc. form probiotics. All the above microbes help in maintaining the intestinal bacteria which help the digestion. They also decrease the harmful bacteria such as Clostridium.
→ Probiotic products : Various products are called probiotic, such as yoghurt, kefir, sauerkraut (pickle of cabbage) and other pickles, dark chocolate, miso soup, oils, corn syrup. artificial sweeteners, sea food microalgae e.g. Spirulina, ‘Chlorella, Blue green algae, etc.
Benefits of probiotics :
- The colonies of useful bacteria are formed in the alimentary canal.
- The harmful microbes can be controlled by reducing their metabolic activities.
- Probiotics improve resistance to fight against diseases.
- Some harmful substances are formed during metabolic activities. Their bad effects are lowered due to probiotics.
- Due to antibiotic treatment, useful bacteria become inactive. Probiotics revitalize them by making them active again.
- Probiotics are used for treatment of diarrhoea.
- In poultry treatment too, probiotics are used.
- Bread is made from flour obtained from cereals.
- The dough is made by mixing together, the baker’s yeast – Saccharomyces cerevisiae, water, salt and other necessary materials.
- The yeast helps in the fermentation and brings about the conversion of sugar into CO2 and ethanol.
- Due to released CO2 the bread becomes spongy.
- Yeast is of two types : Compressed yeast containing carbohydrates, fats, proteins, various vitamins, and minerals. This is used in commercial bakery industry.
- Dry, granular yeast used for domestic use.
- Products produced with yeast become nutritive.
- Vinegar, soya sauce and monosodium glutamate (Ajinomoto) are also produced by microbial fermentation.
- Vinegar Production : Vinegar is 4% acetic acid (CH3COOH).
Uses of vinegar :
- Impart sour taste to food materials.
- Preservation of pickles, sauce, ketchup. chutneys, etc.
- By fermentation of fruit juices, maple syrup. sugar molasses, starch of the roots, etc. with the help of
- yeast Saccharomyces cerevisiae ethanol is obtained.
Preparation of vinegar :
→ Ethanol + Acetobacter and Glucanobacter mixture → microbial degradation → Acetic acid and other by-products → rarefaction of mixture → Separation of Acetic acid → Acetic acid → bleached with potassium ferrocynide → Pasteurization → vey small quantity of SO2 gas is mixed →Vinegar is produced.
Soya sauce :
→ Fungus Aspergillus oryzae is used to ferment the mixture of flour of wheat or rice and soyabean to produce soya sauce. Production of beverages : Coffee, cocoa, wine and cider are the beverages that are produced from Calfea arabica, Theobroma cacao, grapes and apples respectively. For this production various microbes are used.
→ Different enzymes secreted by the glands associated with the digestive system, help in the digestion of the food. The complex food components are broken down to simple absorbable substances due to the enzymatic action.
→ The pepsin and renin secreted by the stomach; amylase, trypsin and lipase secreted by the pancreas and peptidases and other enzymes secreted by the intestinal glands in the small intestine are the enzymes which bring about catalytic activity and help in the digestion.
→ Microbial Enzymes :
- The enzymes obtained by the activity of microbes are used in the industrial processes.
- These microbial enzymes are better than the chemical.catalysts.
- Microbial enzymes work at the low temperature, pH and pressure.
- Energy is saved in the processes using – microbial enzymes.
- There is no need of erosion-proof instruments for the processes.
- Only specific processes are carried out by the enzymes.
- Unnecessary by-products are not formed during the reactions.
- Purification is not needed and hence expenses on purification are reduced.
- Elimination and decomposition of waste material is avoided.
- Enzymes can be reused.
- Microbial enzymes are thus eco-friendly.
→ Some examples of microbial enzymes are:
→ Industries that use microbial enzymes :
- Detergents: Used in cleaning process to remove dirt at low temperature.
- Obtaining glucose and fructose syrup from corn flour using enzymes of bacilli and Streptomyces.
- Industries for cheese manufacture, plant extracts, textile, leather, paper, etc.
→ Some microbes are used in the production of amino acids. These amino acids are used in making commercial products. L-glutamic acid, citric acid, gluconic acid, lactic acid and itaconic acid are such amino acids which are prepared by action of certain microbes on some plant sources.
→ Xanthan gum :
- Xanthomonas species is used to make Xanthan gum by fermentation of starch and molasses.
- It is useful due to properties like solubility in hot and cold water and its high density.
- It is used in the production of pigments, fertilizers, weedicides, textile pigments, tooth pastes, high quality paper, etc.
→ Substances obtained by microbial processing are as follows:
- Citric, Malic and Lactic acid
- Glutamic acid, Lysine, Tryptophan
- Nycin and natamycin
- Ascorbic acid (Vit. C), B12, B2
- Beta carotene, lycopenes, xanthenes, lutein
- Polysaccharides, glycolipids
- Vanillin, Ethyl butyrate (fruit flavour), · Peppermint flavour, essence of various fruits and flowers
→ Their functions are respectively as follows:
- To make the medium acidic
- For binding the proteins
- Microbial restrictor
- Antioxidants, vitamins.
- Edible colours
- Artificial sweetener (low calorie)
→ Carbon compounds obtained from some bacteria and fungi which are able to destroy or prevent the growth of harmful microorganisms are called ‘antibiotics’.
→ It is dangerous to take antibiotics at our own will. They should be taken only when a doctor prescribes to take those. One should not purchase any antibiotic from medical stores without a prescription from a docton One should not use antibiotics according to own will to treat common diseases like a throat infection, common cold or influenza.
→ The dosage of the antibiotics as told by doctor, should be completed, and should not be left half way even if one feels well. Even if we find antibiotic very effective, we should not suggest antibiotics to other people. Antibiotics whose expiry date is over, should never be used.
→ Antibiotics are medicines obtained from different types of bacteria and fungi by carrying out certain processes. Some human diseases and veterinary diseases have been controlled due to antibiotic treatment.
→ Antibiotics which are used against Gram positive and Gram negative bacteria:
- Vancomycin, etc.
- Rifamycin – against tuberculosis.
→ Bio-degradable substances such as animal and plant wastes, dung and urine of the animals, farm wastes, etc. are decomposed in the biogas plant.
→ The best quality manure and fuel is obtained from the biogas plant. The biogas contains methane, carbon dioxide and HS in small proportions.
→ The methanogenic bacteria present in the excreta of the animals bring about the decomposition of the waste matter.
Microbes and Fuels :
→ Methane is obtained from microbes present in the agricultural and industrial waste, by microbial anaerobic decomposition. This reduces the problem of solid waste management.
→ Fermentation of molasses by yeast, Saccharomyces produces ethanol which is a clean, smokeless fuel.
→ The fuel of future is hydrogen gas. It is released when bacteria perform bio-photolysis of water. Bacteria perform the process of photoreduction to release hydrogen.
→ Some industrial chemicals are produced through microbial process. e.g. Some raw materials that are needed for the industrial processes, such as various alcohols, acetone, organic acids, fatty acids, polysaccharides. For plastic and food products some of these materials are used.
→ Bio-fuel : Biofuel is a good and renewable type of energy. They are easily available and in abundance, hence they are called reliable fuels of the future. Biofuel is available in the following three forms :
- Solid : Coal, dung, crop residue
- Liquid : Vegetable oils, alcohol
- Gaseous : Gobar gas and coal gas.
→ Microbial Pollution Control: With the help of suitable microbes, the problem of environmental pollution is tackled. Biogas, plant, compost production, sewage treatment, etc. are the measures in which microbes are used.
→ Land-filling sites:
- The type of degradable waste which is created in the urban areas is dumped in the land fillimg sites which are ‘away from the residential areas.
- The large pits are dug and then lined with plastic sheets. Used for dumping compressed waste.
- It is covered with certain bioreactor substances and specific biochemicals.
- Microbes present therein decompose the biodegradable materials.
- The pit is sealed with soil slurry after it is full
- Compost is formed by decomposition after few days. This is removed and such land filling sites can be reused after removal of compost.
→ Sewage Management:
- In cities, the sewage is sent to processing plant and is treated with microbes.
- Microbes that carry out decomposition, are mixed with sewage. Such microbes are able to destroy pathogens as well as decompose any compounds.
- Upon decomposition of the carbon compounds present in sewage, microbes release methane and Co,
- The phenol oxidizing bacteria decompose Xenobiotic chemicals present in sewage.
- The sludge formed in this process, is used as fertilizer.
- Environmentally safe water is released after microbial treatment done for the sewage water
Some microbes bring about bioremediation of environment, that are used for treating sewage pollution.
→ Clean Technology :
→ Microbes are used to combat increasing soil, land ard water pollution. Pollutior. control can be done by using microbes that digest hydrocarbons.
→ Microbes used in clean technology :
|Microbes performing tasks of cleaning||Function|
|Some microbes||Remove the sulphur from fuels.|
|Thiobacilli and Sulphobacilli||Conversion of heavy metals into compounds before leaching|
|Hydrocarbonoclastic bacteria (HCB): Pseudomonas spp. and Alcanovorax borkumensis||To treat oil spills by destroying the pyridines and other chemicals. Conversion of hydrocarbons into CO2 and water.|
|Vibrio, Ideonella sakaiensis||Decomposition of PET (Polyethylene Terephthalate Polyester)|
|Actinomycetes, Streptomyces, Nocardia, Actinoplanes (all bacteria)||Decomposition of rubber from garbage.|
|Acidophillium spp. and Acidobacillus ferroxidens||Control of soil pollution caused by acid rain.|
|Geobacter||Conversion of salts of uranium into insoluble salts.|
→ There are various causes of oil spills occurring in the marine waters. For example, accidents of oil tankers that transport crude oil, spillage through offshore oil wells, pollutants released through effluents from shore, etc. The oil spills form an oil film on the surface of water. It causes depletion of oxygen in the water. It also contains hazardous hydrocarbons which results in the death of fish.
→ Microbes and Farming :
→ The leguminous plants have root nodules in which the bacteria, Rhizobium resides symbiotically with the plants such as peas, beans, soyabeans, etc. These bacteria supply nitrates and nitrites and amino acids to the plants. They have capacity to convert nitrogen in the soil and air to form such compounds. This is called bacterial nitrogen fixation.
→ In return the plants provide energy in the form of carbohydrates and the place to stay in the root nodules to the bacteria. Some more bacteria and blue green algae such as Anabaena, Nostoc and Azotobacter, are free living in the soil, they too perform similar function of nitrogen fixation Both types of bacteria make the soil fertile and reduce the demand of chemical fertilizers.
→ Microbial Inoculants :
- Microbes-containing inoculants are produced by process of fermentation.
- They are used for spraying on seeds before sowing. Some of them are released into plants.
→ Benefits of microbial inoculants :
- The nutrients are supplied through the microbial inoculants which help in growth of plants.
The nutritional quality of crops is increased.
- Soil pollution caused by chemical fertilizers is prevented by injecting solution containing Azotobacter and artificial nitrogenase. Such methods are adopted in organic farming.
- Chemicals like fluoroacetamide are mixed with soil as chemical pesticides in agriculture. Such harmful substances can be eradicated by using microbes.
→ Bioinsecticides :
- Through biotechnology, bacterial and fungal toxins are directly integrated into plants to protect them from fungal and pest attacks.
- Insects avoid such plants as they are secondarily toxic.
- Some species of fungi and viruses are also used as pesticides. Spinosad, produced through fermentation is used as a blopesticide.
- Biodegradable plastic, polylactic acid is used for garbage bags. This material is eco-friendly.