A small amount of curd added to the fresh milk as inoculum or starter contain millions of LAB, which at suitable temperatures multiply, thus converting milk to curd. During growth, the LAB produces acids that coagulate and partially digest the milk proteins.
Advantages of Process: It increases nutritional value. It checks disease-causing microbes in our stomach. It increases Vitamin B12
The process of anaerobic respiration in which the complex molecules incompletely brakes into simple ones by the microbial action is called fermentation
Fermentation of dough is done for making dosa, idli. CO2 produced in the process gets trapped in gluten and makes idli puffy.
For making bread the microbe used is Baker‘s yeast (Saccharomyces cerevisiae).
Toddy is made from the sap of palm using process of fermentation.
The process is used in cheese making (eg.Swiss cheese by Propionibacterium sharmanii, Roquefort cheese by fungi.). Different varieties of cheese are known by their characteristic texture, flavour and taste, the specificity coming from the microbes used. The bacterium Propionibacterium sharmanii is used in ‘Swiss cheese’ to give it its characteristic holes by producing a large amount of carbon dioxide. ‘Roquefort cheese’ is ripened by growing certain fungi on them to give them their specific flavour.
Microbes as the Source of Food:
Some microbes or their fruiting bodies are directly used as a source of food. They are rich in protein.
Single cell protein (SCP) is the protein extracted, or the cells themselves, from cultivated microbial biomass. The microbes involved are bacteria, fungi and algae. SCP has high protein content. They can be grown on waste products such as whey, which makes it more of an economically- feasible protein source.
SCP can be obtained from bacteria (Bacillus subtilis), fungi (Candida and Saccharomyces cerevisiae), algae (Chlorella).
Fungus like Mushrooms and truffles (bacidomycetes) are directly used as food. They are sugar-free, fat-free. They have low-calorie value. They are rich in proteins, vitamins, minerals and amino acids.
Some common edible mushrooms are white button mushroom (Agaricus bisporus), Paddy straw mushroom (Volvariella Volvacea), Oyster mushroom (Pleurotus florida).
Toadstools are poisonous mushrooms.
Microbes in Industrial Production
Production of Alcoholic Beverages:
Beverages like wine, beer, whisky, Brandy, Rum are produced from malted cereals and fruit juices. Wine and beer produced without distillation. While whisky, brandy, rum produced after distillation.
Microbes used for making wine is Saccharomyces cerevisiaevar. ellipsodeus. ( brewer’s yeast) Different flavours can be obtained by using different flavours.
Beer is made from the fermentation of grains, particularly barley. Microbes used for making beer is Saccharomyces cerevisiae. Steps involved are malting, mashing and fermentation. The fermenting solution is allowed to stand for few days. Then it is clarified, carboxylated and bottled.
Whisky is obtained from fermenting mixed grains of corn, wheat, barley etc. The product of fermentation is distilled.
Production of Organic Acids:
The number of organic acids are obtained by fermentation using microbes.
Some organic acids (microbial source) are as follows. Citric acid (Aspergillus niger), Gluconic acid (Aspergillus niger), Fumaric acid (Rhizopus arrhizus), Acetic acd or vinegar (Acetobacter aceti), Butyric Acid (Clostridium butylicum), Lactic acid. (Lactobacillus).
Production of Vitamins:
Vitamins are complex organic compounds required in very small quantities for normal growth and development of a body.
There are two types of vitamins a) water-soluble (vitamins B and C) and b) fat-soluble (vitamins A, D, E and K).
All vitamins are not produced in the body, hence they are obtained through food and supplements, tablets.
Some important vitamins (microbial source) are as follows. Vitamin B2 (Neurospora gossypii and Eremothecium ashbyi), Vitamin B12 (Pseudomonas denitrificans) and vitamin C (Aspergillus niger).
Production of Antibiotics :
Some secondary metabolites, products of fermentation have therapeutic use.
Penicillin produced by Alexander Fleming from Penicillium notatum while working with Staphylococcus aureus.
Earnest Chain and Howard Plorey awarded Nobel Prize in 1945 for establishing Penicillin as an effective antibiotic.
Penicillin is used to treat diseases like plague, whooping cough, diphtheria, leprosy.
Some important antibiotics(microbial source) are as follows. Chloromycetin (Streptomyces venezuelae), Erythromycin (Streptomyces erythreus), Penicillin (Penicillium chrysogenum), Streptomycin (Streptomyces griseus).
Production of Chemicals :
Lipases used in detergents to remove oil strains from Laundry.
Pectinases and Proteases to clarify bottled juices.
Streptokinase (from Streptococcus) act as clot buster in the treatment of myocardial infraction (heart attack).
An immuno-suppressant Cyclosporin A (Trichoderma polysporum) is used in organ transplant patients.
Statins produced by yeast (Monascus purpureus) used as blood, cholesterol-lowering agent.
Production of Gibberellin:
Gibberellins are a group of growth hormones produced by higher plants and fungi to promote growth by stem elongation.
The first gibberellin was obtained by Japanese scientists Yabuta and Sumiki in 1938 from rice seedlings infected with the fungus Gibberella fujikuroi.
About 15 types of gibberellins are obtained from Gibberella fujikuroi.
Gibberellins are used to induce parthenocarpy in apple, pear etc.
They are also used for breaking dormancy and inducing flowering.
Production of Enzymes:
Enzymes are biocatalyst which are required for initiation or acceleration of biological process in a living organism. These enzymes convert complex substances like starch, proteins and fats into simple absorbable substances.
Now enzymes are produced to give desirable flavours to cheese and butter, sweetness to confectionaries, animal feed, soybean milk, etc.
Some important enzymes (microbial source) are as follows. Invertase (Saccharomyces cerevisiae), Pectinase (Scerotiana libertine), Lipase (Rhisopus spp), Cellulase (Trichoderma konigi).
Dairy Industry :
Products obtained in the dairy industry by microbe activities are cheese, yoghurt, buttermilk, paneer.
Microbes used are species of Streptomyces, Penicillium, Lactobacillus.