Theory:

Not all microorganisms are harmful. Some are useful in day to day life. For example in the preparation of bread, curd, and cakes. Microorganisms are really useful in many industries such as the food industry, agriculture, food preservation, and pharmaceutical industry. It is also helpful in cleaning the environment.
  • Food industry
  • Agriculture
  • Pharmaceutical industry
  • Food industry
While preparing curd, you could have witnessed your mother putting one spoon of curd in milk, which will turn the milk to curd. Doing so, there will be the formation of Lactobacillus which will turn milk into curd. Yeast is another bacteria that is used to add softness and fluffiness to bakery items such as cake and pastries and bread. Yeast is used for fermentation.
Fermentation
Yeast performs fermentation to obtain energy by converting sugar into alcohol. With yeast, large scale production of alcohol is done commercially.
 
Even while making batter for idlis, parottas, bacteria play a key role in adding softness and taste to food.
Have you ever made note of batter which is prepared the previous day which will be only half of the vessel, will be full in the morning. How did that happen? Because of the leavening action of the lactic acid bacterium, L. mesenteroides.
 
Yeast is used in the process of converting maida batter (used for parottas) into the more soft and fluffy batter with improved quantity.
 
Microorganisms can live anywhere starting from plants, animals, inside a cell and everywhere. We are surrounded by microorganisms.