A bacterium capable of poly(${gamma}$-glutamic acid) production was isolated from nonpasteurized soy sauce. It was judged to be a variety of Bacillus subtilis and designated as B. subtilis C1. B. subtilis C1 produced ${gamma}$-PGA in the absence of exogenous glutamic acid; therefore, it is a de novo PGAproducing bacterium. The product produced by B. subtilis C1 was characterized by amino acid analysis to be composed of solely glutamic acid. However, the $H^1-NMR$ spectra showed chemical shifts of glycerol protons in addition to those of authentic ${gamma}$-PGA, indicating that the product is in fact a bioconjugate of ${gamma}$-PGA. The finding is unique, because the microbial production of ${gamma}$-PGA bioconjugate has never been reported before. The molecular mass of the product was over 10,000 kDa as determined by GPC, and $97\%$ of the product was D-glutamate, indicating that L-glutamate was converted to its D-form counterpart by B. subtilis C1.
