Functional myo-Inositol Catabolic Genes of Bacillus subtilis Natto Are Involved in Depletion of Pinitol in Natto (Fermented Soybean)
Soybeans are rich in pinitol (PI; 3-<I>O</I>-methyl-<small>D</small>-<I>chiro</I>-inositol), which improves health by treating conditions associated with insulin resistance, such as diabetes mellitus and obesity. Natto is a food made from soybeans fermented by strains of <I>Bacillus subtilis</I> natto. In the chromosome of natto strain OK2, there is a putative promoter region almost identical to the <I>iol</I> promoter for <I>myo</I>-inositol (MI) catabolic genes of <I>B. subtilis</I> 168. In the presence of MI, the putative <I>iol</I> promoter functioned to induce inositol dehydrogenase, the enzyme for the first-step reaction in the MI catabolic pathway. PI also induced inositol dehydrogenase and the promoter was indispensable for the utilization of PI as well as MI, suggesting that PI might be an alternative carbon source metabolized in a way involving the MI catabolic genes. Natto fermentation studies have revealed that the parental natto strain consumed PI while a mutant defective in the <I>iol</I> promoter did not do so at all. These results suggest that inactivating the MI catabolic genes might prevent PI consumption, retaining it in natto for enrichment of possible health-promoting properties.
- Bioscience, biotechnology, and biochemistry
Bioscience, biotechnology, and biochemistry 70(8), 1913-1920, 2006-08-23
Japan Society for Bioscience, Biotechnology, and Agrochemistry