Microbes such as. Lactobacillus and others commonly called lactic acid bacteria (LAB) grow in milk and convert it into curd. During growth, such bacteria produce adds (mainly lactic add) that coagulate and partially digest the milk proteins. A small amount of curd, known as starter, is added to the milk and kept at a suitable temperature, where lactic acid bacteria multiply in millions and converts milk into curd that also improves its nutritional quality by increasing vitamin BI2. It also checks the growth of disease-causing microbes in the stomach.

Cheese is one of the oldest milk products prepared with the help of microbes.The curd is separated from liquid part or whey to form cheese. Dosa, Upma are fermented preparation of rice and black gram. The two are allowed to ferment for 3-12 hours with air borne Leuconostoc and Streptococcus species of bacteria. Toddy is a traditional drink of some parts of South India which is made by fermentation of sap of palms.

Lactobacillus belongs to the group of bacteria which perform fermentation and convert the sugars into lactic acid in the absence of oxygen. This bacterium is present in the raw milk. This bacterium can also be added to the milk in the form of already synthesized curd. Lactose is the disaccharide sugar present in the milk gets converted to lactic acid. The lactic acid which is produced gives a sour taste and the milk is converted to curd. 

This is one of the examples of physical methods to cause food preservation and is called pasteurization.

Saccharomyces cerevisiae is the fungus which is commonly known as baker's yeast. The yeast cells are added to the batter of idli and dosa. The fungus performs anaerobic fermentation. The fungus utilizes the fermentable sugars and convert them to ethanol and carbon dioxide. The carbon dioxide gas causes the dough to rise and become soft and fluffy. The carbon dioxide bubbles gets trapped in the dough and when baking is done, this bubbles break and forms pores. 

We use microbes or products derived from them everyday. There are various microbes that help us produces so many dairy products. For eg. Yoghurt is produced  commercially with the help of  Lactobacillus bulgaricus and  Streptococcus thermophilus

Lactobacillus helps in curd formation by coagulating and partially digesting the milk proteins.

Lactobacillus acts on the lactose of the milk and converts it into lactic acid. The increased acidity causes the milk proteins (casein) to coagulate and form the curd. So, the correct answer is option B.

• Curdling of milk produces curd which occurs due to the presence of Lactobacillus bacteria which convert milk sugar to lactic acid at high temperatures.
• Curd is rich in minerals like calcium, phasphorus potassium and zinc.
• They are also rich in protein.
  
• They are a good source of vitamins like riboflavin, Vitamin B6, Vitamin B12, pantothenic acid, and Vitamin A. 
• So, the correct answer is 'Calcium'.

Milk is converted into curd by the action of Lacto bacillus. It multiplies and promotes the formation of curd in milk.

Louis Pasteur proposed the germ theory of disease. This theory explains that the disease is caused by the microorganisms which cannot be seen by naked eyes. These are small and microscopic organisms. These organisms are dependent on the host for activities like growth. He demonstrated that fermentation is the result of the action of microorganism on sugar. 

The most common bacteria responsible for fermentation of dairy milk are Lactobacillus species. Bacteria like Lactococcus and Leuconostoc are also used in production of fermented milk products. Lactobacillus produce lactic acid from lactose by the process of glucose fermentation. This also increases acidity and sours and thickens the milk.

Yoghurt are produced from cultures of Lactobacillus and Streptococcus.Acetobacter aceti has no role in production of yoghurt.

Lactobacillus and Streptococcus that are capable of lactic acid fermentation are used in the flavouring of yogurt.

 Smack is one of the street names of heroin which is chemically diacetylmorphine. It is generally produced by the acetylation of crude morphine and is a narcotic analgesic that is used in the treatment of severe pain. Illicit heroin may be smoked or solubilised with a weak acid and then injected.

Propionibacterium Sharmani or P.Sharmani is the bacterium used for the production of a large amount of CO2 for making large holes in cheese.