Methylthioacetaldehyde, a possible intermediate metabolite for the production of volatile sulphur compounds from L-methionine by Lactococcus lactis.

Volatile sulphur compounds (VSCs) production from L-methionine was studied in Lactococcus lactis. In vitro studies with radiolabelled L-methionine and resting cells of L. lactis revealed that L-methionine was initially converted to alpha-keto-gamma-methylthiobutyrate (KMBA) by a transamination reaction. A part of KMBA was subsequently chemically converted to methylthioacetaldehyde, methanethiol and dimethylsulphides. Chemical conversion of KMBA to methylthioacetaldehyde was dependent on pH, Mn(II) and oxygen. Since methanethiol and dimethylsulphide production was highly related to that of methylthioacetaldehyde, the latter compound was proposed as being an intermediate in VSCs production by L. lactis.