초록
<P><B>Background</B></P><P>In the industry, the conventional two-step fermentation method was used to produce 2-keto-<SMALL>L</SMALL>-gulonic acid (2-KGA), the precursor of vitamin C, by three strains, namely, <I>Gluconobacter oxydans</I>, <I>Bacillus</I> spp. and <I>Ketogulonicigenium vulgare</I>. Despite its high production efficiency, the long incubation period and an additional second sterilization process inhibit the further development. Therefore, we aimed to reorganize a synthetic consortium of <I>G. oxydans</I> and <I>K. vulgare</I> for one-step fermentation of 2-KGA and enhance the symbiotic interaction between microorganisms to perform better.</P><P><B>Results</B></P><P>During the fermentation, competition for sorbose of <I>G. oxydans</I> arose when co-cultured with <I>K. vulgare</I>. In this study, the competition between the two microbes was alleviated and their mutualism was enhanced by deleting genes involved in sorbose metabolism of <I>G. oxydans</I>. In the engineered synthetic consortium (H<SUB>6</SUB> + Kv), the yield of 2-KGA (mol/mol) against <SMALL>D</SMALL>-sorbitol reached 89.7 % within 36 h, increased by 29.6 %. Furthermore, metabolomic analysis was used to verify the enhancement of the symbiotic relationship and to provide us potential strategies for improving the synthetic consortium. Additionally, a significant redistribution of metabolism occurred by co-culturing the <I>K. vulgare</I> with the engineered <I>G. oxydans</I>, mainly reflected in the increased TCA cycle, purine, and fatty acid metabolism.</P><P><B>Conclusions</B></P><P>We reorganized and optimized a synthetic consortium of <I>G. oxydans</I> and <I>K. vulgare</I> to produce 2-KGA directly from <SMALL>D</SMALL>-sorbitol. The yield of 2-KGA was comparable to that of the conventional two-step fermentation. The metabolic interaction between the strains was further investigated by metabolomics, which verified the enhancement of the mutualism between the microbes and gave us a better understanding of the synthetic consortium.</P><P><B>Electronic supplementary material</B></P><P>The online version of this article (doi:10.1186/s12934-016-0418-6) contains supplementary material, which is available to authorized users.</P>