Characterization of acetic acid bacteria in traditional acetic acid fermentation of rice vinegar (komesu) and unpolished rice vinegar (kurosu) produced in Japan

Bacterial strains were isolated from samples of Japanese rice vinegar (kome su) and unpolished rice vinegar (kurosu) fermented by the traditional stati c method. Fermentations have never been inoculated with a pure culture sinc e they were started in 1907. A total of 178 isolates were divided into grou ps A and B on the basis of enterobacterial repetitive intergenic consensus- PCR and random amplified polymorphic DNA fingerprinting analyses. The 16S r ibosomal DNA sequences of strains belonging to each group showed similariti es of more than 99% with Acetobacter pasteurianus. Group A strains overwhel mingly dominated all stages of fermentation of both types of vinegar. Our r esults indicate that appropriate strains of acetic acid bacteria have spont aneously established almost pure cultures during nearly a century of komesu and kurosu fermentation.