초록
<P><B>Background</B></P><P>2,3-Butanediol is an important bulk chemical with a wide range of applications. In bacteria, this metabolite is synthesised from pyruvate via a three-step pathway involving α-acetolactate synthase, α-acetolactate decarboxylase and 2,3-butanediol dehydrogenase. Thus far, the best producers of 2,3-butanediol are pathogenic strains, hence, the development of more suitable organisms for industrial scale fermentation is needed. Herein, 2,3-butanediol production was engineered in the Generally Regarded As Safe (GRAS) organism <I>Corynebacterium glutamicum</I>. A two-stage fermentation process was implemented: first, cells were grown aerobically on acetate; in the subsequent production stage cells were used to convert glucose into 2,3-butanediol under non-growing and oxygen-limiting conditions.</P><P><B>Results</B></P><P>A gene cluster, encoding the 2,3-butanediol biosynthetic pathway of <I>Lactococcus lactis</I>, was assembled and expressed in background strains, <I>C. glutamicum</I> Δ<I>ldhA</I>, <I>C. glutamicum</I> Δ<I>aceE</I>Δ<I>pqo</I>Δ<I>ldhA</I> and <I>C. glutamicum</I> Δ<I>aceE</I>Δ<I>pqo</I>Δ<I>ldhA</I>Δ<I>mdh</I>, tailored to minimize pyruvate-consuming reactions, i.e., to prevent carbon loss in lactic, acetic and succinic acids. Producer strains were characterized in terms of activity of the relevant enzymes in the 2,3-butanediol forming pathway, growth, and production of 2,3-butanediol under oxygen-limited conditions. Productivity was maximized by manipulating the aeration rate in the production phase. The final strain, <I>C. glutamicum</I> Δ<I>aceE</I>Δ<I>pqo</I>Δ<I>ldhA</I>Δ<I>mdh</I>(pEKEx2-<I>als,aldB,</I>P<SUB>tuf</SUB><I>butA</I>), under optimized conditions produced 2,3-butanediol with a 0.66 mol mol<SUP>−1</SUP> yield on glucose, an overall productivity of 0.2 g L<SUP>−1</SUP> h<SUP>−1</SUP> and a titer of 6.3 g L<SUP>−1</SUP>.</P><P><B>Conclusions</B></P><P>We have successfully developed <I>C. glutamicum</I> into an efficient cell factory for 2,3-butanediol production. The use of the engineered strains as a basis for production of acetoin, a widespread food flavour, is proposed.</P><P><B>Electronic supplementary material</B></P><P>The online version of this article (doi:10.1186/s12934-015-0362-x) contains supplementary material, which is available to authorized users.</P>