Various microbes through fermentation, help us in making various food items such as curd, bread, idli, dosa, dhokla and drinks. The baker’s yeast or Saccharomyces cerevisiae is used as a fermenting agent in making bread, idlis and dosas. Yeast also helps in wine and beer preparation by fermenting the sugars present in fruit juices or barley to produce alcohol and carbon dioxide. The same principle is used in the production of toddy, made by fermenting the sap of the palm tree. Similarly, aerobic bacteria called Acetobacter converts ethyl alcohol to produce acetic acid or vinegar.
Lactobacillus, also known as lactic acid bacteria or LAB, when added as an inoculum to milk, multiplies in millions in the milk and converts milk sugar lactose into lactic acid. The lactic acid in turn makes the milk thicker and partly digests the milk proteins, resulting in the formation of curd. LAB even increases the quantities of Vitamin B12 in curd.
LAB in human stomach kills the harmful bacteria that enter along with food. Some bacteria are used in preservation and flavouring tea, cheese and tobacco, a process called curing. Different varieties of cheese are distinguished by their characteristic texture, flavour and taste, all of which depend on the choice of the microbe used. Bacteria such as Propionibacterium shermanii produce large holes in Swiss cheese and fungi such as Penicillium roqueforti gives the characteristic flavour in Roquefort cheese.