Metabolic and Process Engineering of <i>Clostridium beijerinckii</i> for Butyl Acetate Production in One Step

Abstract

<i>n</i>-Butyl acetate is an important food additive commonly produced <i>via</i> concentrated sulfuric acid catalysis or immobilized lipase catalysis of butanol and acetic acid. Compared with chemical methods, an enzymatic approach is more environmentally friendly; however, it incurs a higher cost due to lipase production. <i>In vivo</i> biosynthesis <i>via</i> metabolic engineering offers an alternative to produce <i>n</i>-butyl acetate. This alternative combines substrate production (butanol and acetyl-coenzyme A (acetyl-CoA)), alcohol acyltransferase expression, and esterification reaction in one reactor. The alcohol acyltransferase gene ATF1 from <i>Saccharomyces cerevisiae</i> was introduced into <i>Clostridium beijerinckii</i> NCIMB 8052, enabling it to directly produce <i>n</i>-butyl acetate from glucose without lipase addition. Extractants were compared and adapted to realize glucose fermentation with <i>in situ</i> <i>n</i>-butyl acetate extraction. Finally, 5.57 g/L of butyl acetate was produced from 38.2 g/L of glucose within 48 h, which is 665-fold higher than that reported previously. This demonstrated the potential of such a metabolic approach to produce <i>n</i>-butyl acetate from biomass.