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Metab Eng. 2015 Mar;28:169-179. doi: 10.1016/j.ymben.2015.01.006. Epub 2015 Jan 28.

Molecular modulation of pleiotropic regulator CcpA for glucose and xylose coutilization by solvent-producing Clostridium acetobutylicum.

Author information

1
Key Laboratory of Synthetic Biology, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China; University of Chinese Academy of Sciences, Beijing 100049, China.
2
Key Laboratory of Synthetic Biology, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China; Shanghai Collaborative Innovation Center for Biomanufacturing Technology, 130 Meilong Road, Shanghai 200237, China.
3
Key Laboratory of Synthetic Biology, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China; State Key Laboratory of Motor Vehicle Biofuel Technology, Nanyang 473000, China. Electronic address: ygu02@sibs.ac.cn.
4
Key Laboratory of Synthetic Biology, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China; Shanghai Collaborative Innovation Center for Biomanufacturing Technology, 130 Meilong Road, Shanghai 200237, China. Electronic address: whjiang@sibs.ac.cn.

Abstract

Efficient cofermentation of hexose and pentose sugars is essential for ABE (Acetone, Butanol and Ethanol) solvents production from lignocellulosic hydrolysates by Clostridium acetobutylicum, an important industrial microorganism. However, utilization of xylose, the predominant pentose present in lignocellulosic feedstocks, by this anaerobe is limited by CCR (Carbon Catabolite Repression) that is mediated by the catabolite control protein A (CcpA). Here, we reported a novel engineering strategy based on CcpA molecular modulation to overcome the defect. Through CcpA mutagenesis and screening, an amino acid residue, valine 302, was shown to be essential for CcpA-dependent CCR in C. acetobutylicum. When this residue was replaced by asparagine (V302N mutation), CCR could be alleviated and a greatly improved xylose utilization was realized. Transcriptional and DNA binding analysis was then used to elucidate the underlying molecular mechanism. Furthermore, the sol genes (ctfA, ctfB and adhE1) were overexpressed, upon the V302N mutation, to accelerate sugar consumption and solvents formation. The resulting strain (824ccpA-V302N-sol) was capable of using over 90% of the total xylose within 72 h when fermenting a mixture of glucose and xylose (30 g/L glucose and 15 g/L xylose), which was much higher than that (30%) of the control strain 824ccpA-ccpA(C). This is the first report that offered an optimized C. acetobutylicum CcpA with alleviated repression on xylose metabolism, yielding a valuable platform host toward ABE solvents production from lignocellulosic biomass.

KEYWORDS:

C. acetobutylicum; CcpA mutagenesis; Sol overexpression; Xylose and glucose cofermentation

PMID:
25637046
DOI:
10.1016/j.ymben.2015.01.006
[Indexed for MEDLINE]

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