초록
<P>The aim of this study was to develop a bioprocess capable of producing caproic acid using a binary fermentation system consisting of <I>Clostridium kluyveri</I> H068 and <I>Methanogen</I> 166 which could then be applied to the brewing of Chinese strong flavor liquor. We initially explored the mechanism by which the <I>Methanogen</I> 166 strain facilitates caproic acid accumulation, revealing its ability to convert accumulated H<SUB>2</SUB> that is produced by <I>C. kluyveri</I> H068 into methane, thereby eliminating the hydrogen-mediated feedback inhibition that normally constrains <I>C. kluyveri</I> H068 and thus enhancing caproic acid production. In addition, laboratory experiments were conducted to optimize this binary fermentation system, allowing us to determine that the optimum conditions for caproic acid production are a mixed inoculum size of 10% with a <I>C. kluyveri</I> H588/Methanogen 166 inoculation ratio of 2:1 (v/v), a sodium acetate concentration of 20 g/L, a 4% ethanol content (v/v), and a yeast extract concentration of 10 g/L. We further scaled this optimized condition up to use in a 1000 L fermenter and the obtained caproic acid broth was subjected to pit-entry fermentation. Our results demonstrated that this pit-entry fermentation approach was an efficient means of improving the quality of Chinese strong flavor liquor.</P><P><B>Electronic supplementary material</B></P><P>The online version of this article (10.1186/s13568-018-0705-1) contains supplementary material, which is available to authorized users.</P>