Production of methionol from 3-methylthiopropionaldehyde by catalysis of the yeast alcohol dehydrogenase Adh4p.

Methionol is a sulphur-containing aroma compound that contributes to flavors of fermented foods. In this work, a novel method for methionol production was established using 3-methylthiopropionaldehyde (MMP) and alcohol dehydrogenase (ADH). Firstly, expression of seven ADH genes was analyzed in yeast fermentation added with MMP. Only ADH4 displayed an evident increased expression in response to MMP. ADH4 was then over-expressed in Saccharomyces cerevisiae S288c and Escherichia coli BL21, respectively. The recombinant yeast strain S4 produced more methionol than control strain in MMP fermentation. Furthermore, 0.55 g/L of the 42 kDa Adh4p was prepared from E. coli by induced expression and purification. A fed-batch catalysis system was finally established to produce methionol from MMP by Adh4p. In 10 h of continuous catalysis, the conversion rate of MMP maintained 80%~95% and a final yield of 0.2 g/L of methionol was achieved. This work proposed a novel method for methionol production by enzymatic catalysis with a potential application prospect in industry.