Bacterial community characterization and dynamics of indigo fermentation

Indigo fermentation has been traditionally performed for dyeing textiles in Japan. Limited information is available on the microbiota involved and the succession of the bacterial community structure during indigo reduction. We investigated the bacterial community structure associated with indigo fermentation using denaturing gradient gel electrophoresis and clone library analyses of a PCR-amplified 16S rRNA gene in the early phase of fermentation carried out in our laboratory. A marked substitution of Halomonas spp. by Amphibacillus spp. was observed corresponding to the marked change in the state of indigo reduction. Although the reported indigo-reducing bacteria, Alkalibacterium spp., were not predominant in the early phase of fermentation, they were predominant in fermentation liquor aged for 10 months obtained from Date City, Japan, as determined by culture-dependent and culture-independent analyses. Novel indigo-reducing strains, Amphibacillus spp. strain C40 and Oceanobacillus spp. strain A21, were isolated from fermentation liquor aged for 10 months and from liquor aged for 4 days, respectively. It is considered that, in addition to the strains belonging to the genus Alkalibacterium, strains belonging to genera Amphibacillus and Oceanobacillus play important roles in sustaining the reduced state of indigo during fermentation.