Figure 1

Biodegradation-inspired construction of the biosynthetic pathways.

Methylacetoin biodegradation is presented with a dashed line and the constructed biosynthetic pathways are presented using a solid line. The enzymes (gene names in parentheses) for each numbered step are as follows: (1) glycolysis; (2,3) acetolactate synthase and acetolactate decarboxylase (alsS and alsD); (4) acetaldehyde dehydrogenase (acoD); (5) acetoin:2,6-dichlorophenolindophenol oxidoreductase (acoAB); (6) dihydrolipoamide acetyltransferase (acoC); (7) dihydrolipoamide dehydrogenase (acoL); (8) acetoin/methylacetoin reductase (bdhA). Enzymes (5), (6) and (7) form the degradation complex. (6) and (7) need to be deleted to block biodegradation during the biosynthesis. The presence of (4) enhanced the biosynthesis of methylacetoin from acetoin and acetone by improving the reaction thermodynamics.