Metabolic reconstruction of Clostridium acetobutylicum for enhanced production of butyric acid

Junho Bang1, Yu-Sin Jang1, and Sang Yup Lee1,2*

Metabolic and Biomolecular Engineering National Research Laboratory, Department of Chemical and Biomolecular Engineering (BK21 Program), BioProcess Engineering Research Center, Center for Systems and Synthetic Biotechnology, Institute for the BioCentury,1

Department of Bio and Brain Engineering and Bioinformatics Research Center, KAIST, 335

Gwahangno, Yuseong-gu Daejeon 305-701, Republic of Korea2

Butyric acid production by fermentation of renewable resources has been receiving much attention as an alternative to petroleum-derived butyric acid because of the consumersâ?? preference towards natural ingredients for food, pharmaceutical, animal feed supplement, and perfume. Clostridium acetobutylicum has been considered an attractive platform-host for biorefinery due to its metabolic diversity. Considering its capability to overproduce butanol through butyrate, it was thought that butyric acid can also be efficiently produced by this bacterium through metabolic engineering. The pta-ctfB-deficient C. acetobutylicum CEKW, in which genes encoding phosphotransacetylase and CoA-transferase were knocked-out, was assessed for its potential as a butyric acid-producer in fermentations with four controlled pH- values at 5.0, 5.5, 6.0, and 6.4. Furthermore, the CEKW strain was further engineered by knocking-out the adhE1 encoding aldehyde/alcohol dehydrogenase to prevent solvent-production. The simultaneous deletion of the pta-ctfB-adhE1 in C. acetobutylicum resulted in metabolic switch from biphasic to acidogenic fermentation, which enhanced butyric acid-production. [This work was supported by the Technology Development Program to Solve Climate Changes on Systems Metabolic Engineering for Biorefineries from the Ministry of Science, ICT and Future Planning (MSIP) through the National Research Foundation (NRF) of Korea (NRF-2012- C1AAA001-2012M1A2A2026556).]