How do Streptococcus thermophilus and Lactobacillus bulgaricus precipitate the curd of swiss cheese?
lactic acid bacteria ferment the disaccharide lactose present in high amounts in milk to the three-carbon compound lactic acid, which acidifies the milk. this causes the proteins also present in milk to denaturate and coagulate, forming curdles. other causes/methods of curdling can be application of heat, salts or by adding the enzyme chymosin (rennin).