- Lactic acid bacteria
Lactic acid bacteria are Gram-positive cocci and bacilli which ferment glucose, giving lactic acid as more than fifty percent of the end product. Those with bacterial mobility are extremely rare. Those that only produce lactic acid from saccharides are called homofermentative; those that also produce alcohol, acetic acid, carbon dioxide and hydrogen are called heterofermentative.
In kimoto-school shubo, the coccus Leuconostoc mesenteroides grows at almost the same time as the nitrate reducing bacteria. It produces lactic acid and lowers the pH. Then the bacillus Lactobacillus sake begins to grow as the nutrients produced in a slightly acidic environment accumulate, and it begins vigorous acid production. This has the effect of weeding out contaminants.
Apart from lactic acid bacteria which are beneficial to sake brewing, there are malignant lactic acid bacteria which are one stated cause of excessive acidity. These hi-ochi-kin are the cause of so-called hi-ochi infection.