No abstract

No abstract

No abstract

Methionol is a sulfur-containing aroma compound that contributes to the flavors of fermented foods. In this work, a novel method for methionol production was established using 3-methylthiopropionaldehyde (MMP) and alcohol dehydrogenase (ADH). First, 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 overexpressed in Saccharomyces cerevisiae S288c and Escherichia coli BL21. The recombinant yeast strain S4 produced more methionol than control strain in MMP fermentation. Furthermore, 0.55 g/L 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 remained 80− 95%, and a final yield of 0.2 g/L methionol was achieved. This work proposed a novel method for methionol production by enzymatic catalysis with a potential application prospect in industry.

The aminotransferase ARO8 was proved to play an efficient role in conversion of l-methionine into methionol via the Ehrlich pathway in Saccharomyces cerevisiae in our previous work. In this work, the reversible transamination activity of ARO8 for conversion of α-keto-γ-(methylthio) butyric acid (KMBA) into l-methionine was confirmed in vitro. ARO8 was cloned from S. cerevisiae S288c and overexpressed in Escherichia coli BL21. A 2-fold higher aminotransferase activity was detected in the recombinant strain ARO8-BL21, and ARO8 was detected in the supernatant of ARO8-BL21 lysate with IPTG induction by SDS-PAGE analysis. The recombinant ARO8 was then purified and used for transforming KMBA into l-methionine. An approximately 100% conversion rate of KMBA into l-methionine was achieved by optimized enzymatic reaction catalyzed by ARO8. This work fulfilled l-methionine biosynthesis catalyzed by the aminotransferase ARO8 using glutamate and KMBA, which provided a novel method for l-methionine production by enzymatic catalysis with the potential application prospect in industry.