초록
<P><B>Abstract</B></P> <P>Microbial processes can produce a wide range of compounds; however, producing complex and long chain hydrocarbons remains a challenge. Aldol condensation offers a direct route to synthesize these challenging chemistries and can be catalyzed by microbes using aldolases. Deoxyribose-5-phosphate aldolase (DERA) condenses aldehydes and/or ketones to β -hydroxyaldehydes, which can be further converted to value-added chemicals such as a precursor to cholesterol-lowering drugs. Here, we implement a short, aldolase-based pathway in <I>Escherichia coli</I> to produce (<I>R</I>)-1,3-BDO from glucose, an essential component of pharmaceutical products and cosmetics. First, we expressed a three step heterologous pathway from pyruvate to produce 0.3 g/L of (<I>R</I>)-1,3-BDO with a yield of 11.2 mg/g of glucose in wild-type <I>E. coli</I> K12 MG1655. We used a systems metabolic engineering approach to improve (<I>R</I>)-1,3-BDO titer and yield by: 1) identifying and reducing major by-products: ethanol, acetoin, and 2,3-butanediol; 2) increasing pathway flux through DERA to reduce accumulation of toxic acetaldehyde. We then implemented a two-stage fermentation process to improve (<I>R</I>)-1,3-BDO titer by 8-fold to 2.4 g/L and yield by 5-fold to 56 mg/g of glucose ( 11 % of maximum theoretical yield) in strain BD24, by controlling pH to 7 and higher dissolved oxygen level. Furthermore, this study highlights the potential of the aldolase chemistry to synthesize diverse products directly from renewable resources in microbes.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Platform for non-natural chemicals developed using aldol condensation. </LI> <LI> Modular pathway design demonstrated in E. coli for (R)-1,3-BDO production. </LI> <LI> Carbon flux optimized by blocking pyruvate and acetaldehyde-consuming pathways. </LI> <LI> Final (R)-1,3-BDO production: 2.4 g/L and 11% of maximum theoretical yield. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>