Volatile Sulfur-Containing Compounds from Methionine Metabolism in Genetically Modified Lactobacillus helveticus CNRZ32 Strains

摘要

Cystathionine-β-lyase (CBL) catalyzes the conversion of methionine to methanethiol, dimethyl disulfide and dimethyl trisulfide. These three compounds are collectively referred to as volatile sulfur compounds (VSC). Two strains of Lactobadllus helveticus CNRZ32 were evaluated for VSC production; wild-type and a genetically modified variant that produced elevated levels CBL. Whole cell suspensions and cell free extracts were incubated in buffer (pH 6.0) with methionine substrate; furfuryl alcohol was added as an internal standard. Results demonstrated that the modified strain produced ～2-fold higher levels of VSC, primarily dimethyl disulfide. In parallel, NMR was used to substantiate a lyase-mediated pathway by tracking metabolites of uniformly labeled ~(13)C methionine (17.5mM).