Curd production from milk utilizes lactose fermentation into lactic acid by specific bacteria. Commonly employed bacteria include *Lactobacillus acidophilus*, *Lactobacillus delbrueckii* subsp. *bulgaricus*, and *Streptococcus thermophilus*. These microorganisms transform lactose into lactic acid, which reduces pH, leading to the coagulation of milk proteins (casein) and curd formation.
Other microorganisms have distinct functions:
- *Saccharomyces cerevisiae*: Yeast for baking and alcohol fermentation.
- *Aspergillus niger*: Fungus for citric acid and enzyme production.
- *Penicillium notatum*: Fungus for penicillin production.
Therefore, *Lactobacillus acidophilus* is the microorganism responsible for curd production from milk.