Bacteria used in fermented food.

The bacteria used in fermented food mainly include Acetobacter, non-pathogenic Corynebacterium and lactic acid bacteria.

Acetobacter is common in rotten fruits, vegetables, sour juice, vinegar and drinks. It belongs to Gram-negative bacilli, facultative aerobic, but easy to denature. Degraded bacteria are dendritic and filamentous. Gram staining of strains in old cultures often changes. Acetobacter can oxidize ethanol into acetic acid, so it is the main strain to make vinegar.

Non-pathogenic Corynebacterium is usually isolated from soil, water, air and contaminated bacterial Petri dishes or blood plates. Nonpathogenic Corynebacterium such as Corynebacterium glutamicum, Corynebacterium lux and Corynebacterium hydrocarbon decomposition are often used to produce monosodium glutamate (L- glutamate). They can decompose sugar into organic acids, nitrogen-containing substances into ammonium ions, and then further synthesize glutamic acid, which is accumulated in the fermentation broth.

Lactic acid bacteria can produce lactic acid and play a major role in the production of fermented dairy products. According to the characteristics of sugar fermentation, it can be divided into isozyme and heterozyme.

In the fermentation process, isoenzyme can convert 80 ~ 90% lactose in the fermentation broth into lactic acid, with only a small amount of other by-products. Commonly used strains are: Lactobacillus casei, Lactobacillus bulgaricus, Lactobacillus acidophilus, Lactococcus lactis, Streptococcus thermophilus and Lactococcus lactis subspecies succinate.

In the fermentation process, heterotypic fermentation bacteria can convert 50% lactose into lactic acid, and the other 50% sugar into other organic acids, alcohols, carbon dioxide, hydrogen and so on. The strains used in food are Leuconostoc glucan and Leuconostoc creamer.