초록
<P><B>ABSTRACT</B></P><P>Spo0A is a master regulator that governs the metabolic shift of solventogenic <I>Clostridium</I> species such as <I>Clostridium beijerinckii</I>. Its disruption can thus potentially cause a significant alteration of cellular physiology as well as metabolic patterns. To investigate the specific effect of <I>spo0A</I> disruption in <I>C. beijerinckii</I>, a <I>spo0A</I> mutant of <I>C. beijerinckii</I> was characterized in this study. In a batch fermentation with pH control at 6.5, the <I>spo0A</I> mutant accumulated butyrate and butanol up to 8.96 g/L and 3.32 g/L, respectively from 60 g/L glucose. Noticing the unique phenotype of the <I>spo0A</I> mutant accumulating both butyrate and butanol at significant concentrations, we decided to use the <I>spo0A</I> mutant for the production of butyl butyrate that can be formed by the condensation of butyrate and butanol during the ABE fermentation in the presence of the enzyme lipase. Butyl butyrate is a value‐added chemical that has numerous uses in the food and fragrance industry. Moreover, butyl butyrate as a biofuel is compatible with Jet A‐1 aviation kerosene and used for biodiesel enrichment. In an initial trial of small‐scale extractive batch fermentation using hexadecane as the extractant with supplementation of lipase CalB, the <I>spo0A</I> mutant was subjected to acid crash due to the butyrate accumulation, and thus produced only 98 mg/L butyl butyrate. To alleviate the butyrate toxicity, the biphasic medium was supplemented with 10 g/L CaCO<SUB>3</SUB> and 5 g/L butanol. The butyl butyrate production was then increased up to 2.73 g/L in the hexadecane layer. When continuous agitation was performed to enhance the esterification and extraction of butyl butyrate, 3.32 g/L butyl butyrate was obtained in the hexadecane layer. In this study, we successfully demonstrated the use of the <I>C. beijerinckii spo0A</I> mutant for the butyl butyrate production through the simultaneous ABE fermentation, condensation, and extraction. Biotechnol. Bioeng. 2017;114: 106–112. © 2016 Wiley Periodicals, Inc.</P>