What are the uses of microorganisms?
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Household Products
1. Dairy Products:
Lactic acid bacteria (LAB) like lactobacillus are added to milk. It converts lactose sugar of milk into lactic acid. Lactic acid causes coagulation and partial digestion of milk protein casein. Milk is changed into curd, yoghurt and cheese. The starter or inoculum used in preparation of milk products actually contains millions of LAB.
(i) Curd:
Indian curd is prepared by inoculating skimmed and cream milk with Lactobacillus acidophilus at a temperature of about 40°C or less. Curd is more nutritious than milk as it contains a number of organic acids and vitamins including B12. LAB present in curd also checks growth of disease causing microbes in stomach and other parts of digestive tract. Curd is eaten as such, salted or sweetened. Curd is churned to prepare lassi. It is also used to obtain butter and butter milk.
(ii) Yoghurt (= yogurt):
It is produced by curdling milk with the help of Streptococcus thermophiles and Lactobacillus bulgaricus. The temperature is maintained at about 45°C (40°^6°C) for four hours. It has a flavour of lactic acid and acetaldehyde. Yoghurt is often sweetened and mixed with fruit.
(iii) Butter Milk:
It is acidulated product which is formed by inoculating skimmed milk with starter culture of Streptococcus cremoris, S. lactis, Lactobacillus acidophilus, Leuconostoc species at 22°C for 18 hours. Acidulated liquid left after churning of butter from curd is also called butter milk.
(iv) Sour Cream:
Cream obtained by churning of milk is inoculated with Sterptococcus lactis for producing lactic acid and Leuconostoc cremoris for imparting the characteristic flavour.
(v) Cheese:
It is one of the oldest milk products prepared with the help of microbes. The curd is separated from liquid part or whey to form cheese. Depending upon water content, cheese is of three types -soft (50-80% water), semihard (about 45% water) and hard (less than 40% water).
The method of preparing cheese with the help of microbes was known in Asia and Europe long before Christ. There are several varieties of cheese with different texture, flavour and taste. Curdling is done with the help of lactic acid bacteria and enzyme rennin (= Casein coagulase, chymosin), rennet (from Calf’s stomach) or fruit extract of Withania coagulans. In preparation of raw cheese milk is curdled with the help of lactic acid bacteria. The curd is heated gently to separate cheese from whey.
Any liquid left in cheese is allowed to drain by hanging it in cloth. Unripened or Cottage cheese is prepared by single step fermentation which involves inoculation of skimmed milk with cheese culture (e.g., Lac tobacillus, Acetobacter, Saccharomyces, Rhizopus, Amylomyces) and addition of rennin or rennet after 1-2 hours. Curd is placed in cloth lined porous containers for draining out whey.
Ripened cheese is prepared from unripened cheese by first dipping in brine, wiping and then maturation with different strain of bacteria and fungi. It takes 1-16 months for ripening. Large holed swiss cheese is ripened with the help of CO2 producing (causing holes) bacterium called Propionibacterium sharmanii. Roquefort cheese uses Penicillium roqueforti while Camembert cheese employs Penicillium camemberti for ripening.
2. Bread:
Selected strains of Baker’s Yeast, Saccharomyces cerevisiae, are grown on molasses. When sufficient growth has occurred, Baker’s Yeast is harvested and converted into either powder or cakes. A small quantity of Baker’s Yeast is added to wheat flour. The same is needed. The kneaded flour is kept at a warm temperature for a few hours. It swells up. The phenomenon is called leavening. Leavening is caused by secretion of three types of enzymes by yeast.
They are amylase, maltase and zymase. Amylase causes breakdown of a small quantity of starch into maltose sugar. Maltase converts maltose into glucose. Glucose is acted upon by zymase. Zymase is a complex of several enzymes of anaerobic respiration which brings about fermentation. Fermentation of glucose mainly forms ethyl alcohol and carbon dioxide. The two cause swelling or leavening of the dough. The leavened dough is baked. Both carbon dioxide and ethyl alcohol evaporate making the bread porous and soft.
3. Dosa, Uppma and Idli:
They are fermented preparation of rice and Black Gram (vem. Urad). The two are allowed to ferment for 3-12 hours with air borne Leuconostoc and Streptococcus species of bacteria. CO2 produced during fermentation causes puffing up of the dough.
4. Jalebi:
The semi-liquid dough of fine flour of Wheat is fermented with yeast, fried in the form of coils and dipped in sugar syrup to obtain Jalebi. Imriti is similarly prepared from Black Gram flour.
1. Dairy Products:
Lactic acid bacteria (LAB) like lactobacillus are added to milk. It converts lactose sugar of milk into lactic acid. Lactic acid causes coagulation and partial digestion of milk protein casein. Milk is changed into curd, yoghurt and cheese. The starter or inoculum used in preparation of milk products actually contains millions of LAB.
(i) Curd:
Indian curd is prepared by inoculating skimmed and cream milk with Lactobacillus acidophilus at a temperature of about 40°C or less. Curd is more nutritious than milk as it contains a number of organic acids and vitamins including B12. LAB present in curd also checks growth of disease causing microbes in stomach and other parts of digestive tract. Curd is eaten as such, salted or sweetened. Curd is churned to prepare lassi. It is also used to obtain butter and butter milk.
(ii) Yoghurt (= yogurt):
It is produced by curdling milk with the help of Streptococcus thermophiles and Lactobacillus bulgaricus. The temperature is maintained at about 45°C (40°^6°C) for four hours. It has a flavour of lactic acid and acetaldehyde. Yoghurt is often sweetened and mixed with fruit.
(iii) Butter Milk:
It is acidulated product which is formed by inoculating skimmed milk with starter culture of Streptococcus cremoris, S. lactis, Lactobacillus acidophilus, Leuconostoc species at 22°C for 18 hours. Acidulated liquid left after churning of butter from curd is also called butter milk.
(iv) Sour Cream:
Cream obtained by churning of milk is inoculated with Sterptococcus lactis for producing lactic acid and Leuconostoc cremoris for imparting the characteristic flavour.
(v) Cheese:
It is one of the oldest milk products prepared with the help of microbes. The curd is separated from liquid part or whey to form cheese. Depending upon water content, cheese is of three types -soft (50-80% water), semihard (about 45% water) and hard (less than 40% water).
The method of preparing cheese with the help of microbes was known in Asia and Europe long before Christ. There are several varieties of cheese with different texture, flavour and taste. Curdling is done with the help of lactic acid bacteria and enzyme rennin (= Casein coagulase, chymosin), rennet (from Calf’s stomach) or fruit extract of Withania coagulans. In preparation of raw cheese milk is curdled with the help of lactic acid bacteria. The curd is heated gently to separate cheese from whey.
Any liquid left in cheese is allowed to drain by hanging it in cloth. Unripened or Cottage cheese is prepared by single step fermentation which involves inoculation of skimmed milk with cheese culture (e.g., Lac tobacillus, Acetobacter, Saccharomyces, Rhizopus, Amylomyces) and addition of rennin or rennet after 1-2 hours. Curd is placed in cloth lined porous containers for draining out whey.
Ripened cheese is prepared from unripened cheese by first dipping in brine, wiping and then maturation with different strain of bacteria and fungi. It takes 1-16 months for ripening. Large holed swiss cheese is ripened with the help of CO2 producing (causing holes) bacterium called Propionibacterium sharmanii. Roquefort cheese uses Penicillium roqueforti while Camembert cheese employs Penicillium camemberti for ripening.
2. Bread:
Selected strains of Baker’s Yeast, Saccharomyces cerevisiae, are grown on molasses. When sufficient growth has occurred, Baker’s Yeast is harvested and converted into either powder or cakes. A small quantity of Baker’s Yeast is added to wheat flour. The same is needed. The kneaded flour is kept at a warm temperature for a few hours. It swells up. The phenomenon is called leavening. Leavening is caused by secretion of three types of enzymes by yeast.
They are amylase, maltase and zymase. Amylase causes breakdown of a small quantity of starch into maltose sugar. Maltase converts maltose into glucose. Glucose is acted upon by zymase. Zymase is a complex of several enzymes of anaerobic respiration which brings about fermentation. Fermentation of glucose mainly forms ethyl alcohol and carbon dioxide. The two cause swelling or leavening of the dough. The leavened dough is baked. Both carbon dioxide and ethyl alcohol evaporate making the bread porous and soft.
3. Dosa, Uppma and Idli:
They are fermented preparation of rice and Black Gram (vem. Urad). The two are allowed to ferment for 3-12 hours with air borne Leuconostoc and Streptococcus species of bacteria. CO2 produced during fermentation causes puffing up of the dough.
4. Jalebi:
The semi-liquid dough of fine flour of Wheat is fermented with yeast, fried in the form of coils and dipped in sugar syrup to obtain Jalebi. Imriti is similarly prepared from Black Gram flour.
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Microorganisms are used in the preparation of curd , bread and cake .
They are also used in cleaning up of the environment .
In agriculture they are used to increase soil fertility by fixing nitrogen.
Microorganisms have been used for production of alcohol since ages .
They are also used in preparation of medicines .
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