Abstract
In the manufacturing process of fermented foods, such as bean paste, soy sauce, pickles, and alcohol, lactic acid bacteria produce lactic acid and play an important role in suppressing the growth of other microorganisms by lowering pH. Vinegar is one of the fermented foods and is well known for the high antimicrobial activity. The antimicrobial activity of acetic acid is partly due to lowering pH in environment as well as that of lactic acid. Since acetic acid is a hydrophobic small molecule which passes easily through the phospholipid bilayer of the bacterial membrane, it shows the higher antimicrobial activity compared with lactic acid.Although acetic acid produced by acetic acid bacteria becomes stress for even the acetic acid bacteria themselves, they can be grown under highly concentrated acetic acid conditions. Several molecularmachineries being responsible for acetic acid tolerance in acetic acid bacteria have been reported, including i) prevention of acetic acid influx into cell, ii) acetic acid assimilation, iii) acetic acid efflux by transporter or pump, and iv) protection of cytoplasmic proteins against denature by general stress proteins.Since the acetic acid tolerance in acetic acid bacteria is conferred by several mechanisms, the mechanisms are introduced in this review.
