Class 12 Biology

Microbes in Human Welfare

Microbes in Households Products

Lactic Acid Bacteria

Lactobacillus and many other bacteria cause conversion of milk into curd. These bacteria are commonly called Lactic Acid Bacteria or LAB. These bacteria produce acids that coagulate and partially digest milk proteins during curdling of milk. Curd helps in increasing vitamin B12 in our stomach. LAB plays important role in checking disease causing microbes in our stomach.

Baker’s Yest

Saccharomyces cerevisiae is commonly known as Baker’s yeast. It is used for carrying out fermentation in dough for making bread. Microbes are also used for fermentation in batter for dosa, fermentation of fish, soyabean, bamboo shoot, cheese, etc. The large holes in ‘Swiss cheese’ are due to production of a large amount of CO2 by a bacterium called Propionibacterium sharmani. The ‘Roquefort cheese’ is ripened by a specific fungi.

Microbes in Industrial Products

Fermented Beverages

Beverages; like wine, beer, whisky, brandy, rum, etc. are made because of fermentation of fruit juice by microbes. Sachharomyces cerevisiae is used for fermenting malted cereals and fruit juices to produce ethanol; in this case.


A substance which acts against bacteria is called antibiotic. An antibiotic is a chemical substance that can kill or retard the growth of bacteria. Penicillin was the first antibiotic to be discovered. It was discovered by Alexander Fleming. Its full potential as an effective antibiotic was established much later by Ernest Chain and Howard Florey. Fleming, Chain and Florey were conferred with the Nobel Prize in 1945 for this breakthrough. Penicillin is made from a fungus called Penicillium notatum. Many other antibiotics are made from microorganisms.

Chemicals, Enzymes and other Bioactive Molecules: Certain chemicals; like organic acids, alcohols and enzymes are commercially made with help from microbes. Some examples are given in this table.

MicrobeChemical Produced
Aspergillus niger (fungus)Citric acid
Acetobater aceti (bacterium)Acetic acid
Clostridium butylicum (bacterium)Butyric acid
Lactobacillus (bacterium)Lactic acid
Saccharomyces cerevisiae (fungus)Ethanol
Streptococcus (bacterium)Streptokinase (used as clot buster for removing clots from myocardial infarction patient)
Trichoderma polysporum (fungus)Cyclosporine (immunosuppressive agent used in organ transplant patients)
Monascus purpurues (fungus)Statins (cholesterol lowering agents)