title: Identification and inactivation of pleiotropic regulator CcpA to eliminate glucose repression of xylose utilization in Clostridium acetobutylicum.
abstract: D-xylose utilization is a key issue for lignocellulosic biomass fermentation, and a major problem in this process is carbon catabolite repression (CCR). In this investigation, solvent-producing bacterium Clostridium acetobutylicum ATCC 824 was metabolically engineered to eliminate D-glucose repression of d-xylose utilization. The ccpA gene, encoding the pleiotropic regulator CcpA, was experimentally characterized and then disrupted. Under pH-controlled conditions, the ccpA-disrupted mutant (824ccpA) can use a mixture of D-xylose and D-glucose simultaneously without CCR. Moreover, this engineered strain produced acetone, butanol and ethanol (ABE) at a maximal titer of 4.94, 12.05 and 1.04 g/L, respectively, which was close to the solvent level of maize- or molasses-based fermentation by wild type C. acetobutylicum. Molar balance analysis for improved process of mixed sugars utilization also revealed less acid accumulation and more butanol yield by the engineered strain as compared to the wild type. This study offers a genetic modification strategy for improving simultaneous utilization of mixed sugars by Clostridium, which is essential for commercial exploitation of lignocellulose for the production of solvents and biofuels.
authors.affiliation: Key Laboratory of Synthetic Biology, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China.
authors.forename: Cong
authors.initials: C
authors.lastname: Ren
authors.forename: Yang
authors.initials: Y
authors.lastname: Gu
authors.forename: Shiyuan
authors.initials: S
authors.lastname: Hu
authors.forename: Yan
authors.initials: Y
authors.lastname: Wu
authors.forename: Pan
authors.initials: P
authors.lastname: Wang
authors.forename: Yunliu
authors.initials: Y
authors.lastname: Yang
authors.forename: Chen
authors.initials: C
authors.lastname: Yang
authors.forename: Sheng
authors.initials: S
authors.lastname: Yang
authors.forename: Weihong
authors.initials: W
authors.lastname: Jiang
mesh_terms: D001426:Bacterial Proteins / Q000502:physiology*; D046969:Clostridium acetobutylicum / Q000502:physiology*; D024861:Genetic Enhancement / Q000379:methods*; D058685:Genetic Pleiotropy / Q000235:genetics*; D005947:Glucose / Q000378:metabolism*; D012097:Repressor Proteins / Q000235:genetics*; D014994:Xylose / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D012097:Repressor Proteins; D014994:Xylose; D005947:Glucose