· Lactobacillus or Lactic acid bacteria (LAB):
- It converts milk to curd by producing acids that coagulate and partially digest the milk proteins.
- Fresh milk can be converted to curd by adding some curd containing LAB. It also increases vitamin B12 in curd.
- In stomach, LAB helps to check pathogens.
· Bacterial fermentation (anaerobic respiration) in dough is used to make foods such as dosa, idli etc. The puffed-up appearance of dough is due to the production of CO2.
· Baker’s Yeast (Saccharomyces cerevisiae): It is used to make bread by fermenting dough.
· Toddy is made by fermenting sap from palms.
· Microbes are used to ferment fish, soya bean & bamboo-shoots and to produce cheeses.
· Swiss cheese has large holes due to production of CO2 by Propionibacterium sharmanii (a bacterium).
Roquefort cheese is ripened by growing a fungus (Penicillium roqueforti) on them.
Production of beverages, antibiotics etc. on an industrial scale, requires growing microbes in very large vessels (fermentors).
- Saccharomyces cerevisiae (Brewer’s yeast) is used in the production of beverages by fermenting malted cereals and fruit juices to produce ethanol.
- Wine & Beer are produced without distillation.
- Whisky, Brandy, Rum, Gin, Arrack etc. are produced by distillation of fermented broth.
- Chemical substances produced by some microbes and can kill or retard the growth of pathogens.
- They are used to treat plague, whooping cough, diphtheria, leprosy etc.
- Penicillin: First antibiotic discovered by Alexander Fleming. He observed that Staphylococci could not grow around a mould (Penicillium notatum) growing in unwashed culture plates. He extracted penicillin from it.
- Earnest Chain and Howard Florey established its full potential as an effective antibiotic.
- Fleming, Chain & Florey were awarded Nobel Prize (1945).
Chemicals, enzymes & other bioactive molecules
1. Organic acids: Acid producer microbes include
Aspergillus niger (a fungus) : Citric acid
Acetobacter aceti (a bacterium) : Acetic acid
Clostridium butylicum (a bacterium) : Butyric acid
Lactobacillus (a bacterium) : Lactic acid
2. Alcohol: Yeast (S. cerevisiae) is used to produce ethanol.
· Lipases: Used in detergent formulations. Help to remove oily stains from the laundry.
· Pectinases & Proteases: To clarify bottled juices.
· Streptokinase: Produced by Streptococcus. Used as a ‘clot buster’ to remove clots from the blood vessels of patients who have myocardial infarction.
4. Cyclosporine A: Produced by Trichoderma polysporum (fungus). Used as an immunosuppressive agent in organ transplant patients.
5. Statins: Produced by Monascus purpureus (a yeast). Used as blood-cholesterol lowering agents. It inhibits the enzymes responsible for synthesis of cholesterol.