Lactobacillus

Lactobacillus is a helpful bacterium that converts milk into curd by changing milk sugar into an acid.

• It uses the sugar present in milk, called lactose, as its food.
• As it grows and multiplies, it produces lactic acid. This acid makes the milk proteins clump together, turning liquid milk into thicker curd.
• Lactic acid also gives curd its sour taste and helps stop many harmful microbes from growing, so curd stays good for longer than milk.
• Warmth matters: Lactobacillus works faster in warm conditions, which is why curd sets well in summer or when kept in a warm place.
• The same kind of fermentation by Lactobacillus (often along with other bacteria) helps make foods like idli/dosa batter rise and develop a pleasant taste and smell.

So, Lactobacillus is an example of a microorganism that is not only harmless but useful in making and preserving food.