Notes-Class 10-Science & Technology-2-Chapter-7-Introduction to Microbiology-Maharashtra Board

Yoghurt production :

Method of industrial production of yoghurt :

• Yoghurt is one of the milk product produced from milk with the help of lactobacilli (inoculant).
• In the industrial production of yoghurt, the milk is added with condensed milk powder. This increases the protein content of the milk. Then this milk is subjected to fermentation.
• Milk is boiled and then it is cooled till it becomes lukewarm.
• Then the bacterial strains of Streptococcus thermophilus and Lactobacillus delbrueckii are added to this lukewarm milk in 1:1 proportion.
• The Streptococcus bacteria convert the milk into solution containing lactic acid. This makes the proteins to gel out. It makes the yoghurt dense.
• The lactobacilli helps in the formation of acetaldehyde like compounds giving a characteristic taste to the yoghurt.
• For commercial reasons, various fruit juices can also be mixed with yoghurt to impart different flavours forming Strawberry yoghurt, banana yoghurt, etc.
• The pasteurization is carried out to Increase the shelf life of yoghurt and improve its probiotic properties.

Butter:

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 :

(1) Cheese is produced from cow milk in the entire world. Initially, chemical and microbiological tests of milk done.

(2) Lactobacillus lactis, Lactobacillus cremoris, and Streptococcus thermophilus colours added to the milk.

(3) Milk turns sour > whey (water in yoghurt) is removed to make milk dense.

(4) Protease enzyme from fungi is used at present to produce vegetarian cheese.

(5) Previously, rennet enzyme, from alimentary canal of cattle was used.

(6) Whey is completely separated from yoghurt.

(7) To summarise, the steps of process of cheese formation : cutting the solid yoghurt into pieces → washing → rubbing → salting → mixing of essential microbes + pigments + flavours → Cheese is pressed and cut into pieces → stored for ripening.

Different Types of cheese :

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 cheese 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.

• Mozzarella cheese is used for pizza.
• Cheddar and Swiss, Blue cheese these cheese are used for burgers.
• Sandwich and other western foods use different types of cheese. E.g. Goat Cheese, Camembert, Cotija, Chévre, Feta, Emmental, Gouda, Taleggio, Parmigiano, Regginano, Manchego and Monterey,
• Parmesan are some of the cheese consumed world-wide especially in the Europe and America.

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 diarrhea,
• In poultry treatment too, probiotics are used.

Bread :

• 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 conversation of sugar into carbon dioxide, and ethanol.
• Due to released CO₂ the bread becomes spongy.
• Yeast is of two types : (a) Compressed yeast containing carbohydrates, fats, proteins, various vitamins, and minerals. This is used in commercial bakery industry. (b) 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.

Yeast:

 Yeast is of two types : (a) Compressed yeast containing carbohydrates, fats, proteins, various vitamins, and minerals. This is used in commercial bakery industry. (b) 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 Caffea arabica, Theobroma cacao, grapes and apples respectively. For this production various microbes are used.

Some examples of microbial enzymes are :

1. oxidoreductases
2. transferases
3. hydrolases
4. lyases
5. lsomerases
6. ligases

Use of microbial enzymes in Industries:

1. Detergents : Used in cleaning process to remove dirt at low temperature.
2. Obtaining glucose and fructose syrup from corn flour using enzymes of bacilli and Streptomyces.
3. Industries for cheese manufacture, plant extracts, textile, leather, paper, etc.

Enzymes in human digestive system :

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 he pancreas
• Peptidases and other enzymes secreted by the intestinal glands in the small intestine.

These are the enzymes which bring about catalytic activity and help in the digestion.

Amino acids: 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.

Antibiotics : Carbon compounds obtained from some bacteria and fungi which are able to destroy or prevent the growth of harmful micro-organisms are called ‘antibiotics’.

In medical field 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 : (1)Penicillin, (2) Cephalosporins (3) Monobactam (4) Bacitracin (5) Erythromycin (6) Gentamycin (7) Neomycin (8) Streptomycin (9) Tetracyclines (10) Vancomycin, (11) Rifamycin - against tuberculosis.

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.

Biogas plant : 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 H₂S in small proportion.
• The methanogenic bacteria present in the excreta of the animals bring about the decomposition of the waste matter.

Land-filling sites :

• The type of degradable waste which is created in the urban areas is dumped in the land filling sites which are away from the residential areas.
• The large pits dug and then lined with plastic sheets are used for dumping compressed waste.
• It is covered with certain bioreactor substances and specific bio-chemicals.
• 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 CO₂. Xenobiotic chemicals are present in sewage. The phenol oxidizing bacteria decompose such chemicals.
• 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. They are used for treating sewage pollution.

Microbes & Functions in cleaning -

• 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 fungi) : Decomposition of rubber from garbage.
• Acidophillium spp. And Acidobacillus ferroxidens : Control of soil a pollution caused by acid rain.
• Geobacter : Conversion of salts of uranium into insoluble salts.

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 due to use of chemical pesticides in agriculture. Such harmful substances can be eradicated by using microbes.