Question

Write a full description of the importance and different types of fermentation carried out by bacteria.

Answer 1

The process of conversion of sugar or starch into alcohal or an acid under the influence of bacteria or yeast (microorganism).

Examples are :

1. Yoghurt : it is fermented milk. The solid content of milk is raised to 11 - 15 %. Milk is heated to 80°c for half an hour. It is cooled to 40°c and mixed with inoculum containing streptococcus thermophilus and lactobacillus bulgaricus.

2 . Kefir : it is fermented milk where a mixture of lactic acid bacteria ( lactobacillus kefir ) and yeast are used as kefir grain. Kefir contains small amount of ethanol, CO2 , acetaldehyde and diacetyl.

3. Cheese : It is pressed and flavoured milk curd which became component of human diet. Cottage milk cheese is unripened soft cheese prepared by inoculating skimmed milk first with cheese culture ( streptococcus lactis, S. Cremoris, Leuconostoc citrovorum ) and then rennin or chymosin.

Roquefort cheese employs penicillium roquefortii for ripennig .

Swiss cheese has large hole produced by carbon dioxide given out by bacterium propionibacterium sharmanii.

4. Sausages : They are fermented meats which posses particular flavors and tastes. The most common employed microbe is lactic acid bacteria pediococcus cerevisiae.

5. Fermented vegetables : cabbage , carrot , cucumber , leafy vegetables are also fermented with different bacteria which increases texture, flavours , and tastes.

6 : Single cell proteins : it is protein rich microbial biomass which can be used as food and feed.e.g ; Methylophilus methylotrophus. SCP has all the essential amino acids.

7.Toddy : Coconut water is fermented to produce refreshing drink called toddy.