Final answer:
Lactic acid is the fermentation product that is useful in the manufacture of cheese, and it is produced through homolactic fermentation by lactic acid bacteria such as Lactobacillus.
Step-by-step explanation:
The fermentation product useful in the manufacture of cheese is lactic acid. During the cheese production process, bacteria such as Lactobacillus, Leuconostoc, and Streptococcus undergo lactic acid fermentation, which plays a crucial role. These bacteria, known collectively as lactic acid bacteria (LAB), transform sugars into lactic acid. The high acidity from lactic acid fermentation denatures the milk proteins, causing the milk to solidify and form cheese. This process is specifically known as homolactic fermentation when lactic acid is the sole product. Different strains of these bacteria are used for various types of cheese, contributing to their distinctive flavors and textures.