title: Modulation of the Acetone/Butanol Ratio during Fermentation of Corn Stover-Derived Hydrolysate by Clostridium beijerinckii Strain NCIMB 8052.
abstract: Producing biobutanol from lignocellulosic biomass has shown promise to ultimately reduce greenhouse gases and alleviate the global energy crisis. However, because of the recalcitrance of a lignocellulosic biomass, a pretreatment of the substrate is needed which in many cases releases soluble lignin compounds (SLCs), which inhibit growth of butanol-producing clostridia. In this study, we found that SLCs changed the acetone/butanol ratio (A/B ratio) during butanol fermentation. The typical A/B molar ratio duringClostridium beijerinckiiNCIMB 8052 batch fermentation with glucose as the carbon source is about 0.5. In the present study, the A/B molar ratio during batch fermentation with a lignocellulosic hydrolysate as the carbon source was 0.95 at the end of fermentation. Structural and redox potential changes of the SLCs were characterized before and after fermentation by using gas chromatography/mass spectrometry and electrochemical analyses, which indicated that some exogenous SLCs were involved in distributing electron flow toC. beijerinckii, leading to modulation of the redox balance. This was further demonstrated by the NADH/NAD+ratio andtrxBgene expression profile assays at the onset of solventogenic growth. As a result, the A/B ratio of end products changed significantly duringC. beijerinckiifermentation using corn stover-derived hydrolysate as the carbon source compared to glucose as the carbon source. These results revealed that SLCs not only inhibited cell growth but also modulated the A/B ratio duringC. beijerinckiibutanol fermentation.IMPORTANCEBioconversion of lignocellulosic feedstocks to butanol involves pretreatment, during which hundreds of soluble lignin compounds (SLCs) form. Most of these SLCs inhibit growth of solvent-producing clostridia. However, the mechanism by which these compounds modulate electron flow in clostridia remains elusive. In this study, the results revealed that SLCs changed redox balance by producing oxidative stress and modulating electron flow as electron donors. Production of H2and acetone was stimulated, while butanol production remained unchanged, which led to a high A/B ratio duringC. beijerinckiifermentation using corn stover-derived hydrolysate as the carbon source. These observations provide insight into utilizingC. beijerinckiito produce butanol from a lignocellulosic biomass.
authors.affiliation: Key Laboratory of Biofuel, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, Qingdao, China.
authors.forename: Zi-Yong
authors.initials: ZY
authors.lastname: Liu
authors.affiliation: School of Resources and Civil Engineering, Northeastern University, Shenyang, China.|College of Chemistry, Chemical Engineering and Environmental Engineering, Liaoning University of Petroleum and Chemical Technology, Fushun, China.
authors.forename: Xiu-Qing
authors.initials: XQ
authors.lastname: Yao
authors.affiliation: Sinopec Fushun Research Institute of Petroleum and Petrochemicals, Fushun, China.
authors.forename: Quan
authors.initials: Q
authors.lastname: Zhang
authors.affiliation: Key Laboratory of Biofuel, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, Qingdao, China.
authors.forename: Zhen
authors.initials: Z
authors.lastname: Liu
authors.affiliation: Key Laboratory of Biofuel, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, Qingdao, China.
authors.forename: Ze-Jie
authors.initials: ZJ
authors.lastname: Wang
authors.affiliation: Key Laboratory of Biofuel, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, Qingdao, China.
authors.forename: Yong-Yu
authors.initials: YY
authors.lastname: Zhang
authors.affiliation: Key Laboratory of Biofuel, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, Qingdao, China lifl@qibebt.ac.cn.
authors.forename: Fu-Li
authors.initials: FL
authors.lastname: Li
mesh_terms: D000096:Acetone / Q000378:metabolism*; D018533:Biomass; D000440:Butanols / Q000378:metabolism*; D046970:Clostridium beijerinckii / Q000378:metabolism*; D005285:Fermentation; D008031:Lignin / Q000378:metabolism; D009243:NAD; D012997:Solvents / Q000378:metabolism; D003313:Zea mays / Q000378:metabolism*
chemical_list: D000440:Butanols; D012997:Solvents; D009243:NAD; C036909:lignocellulose; D000096:Acetone; D008031:Lignin
keywords: A/B ratio; Clostridium; NADH/NAD+ ratio; corn stover; soluble lignin compounds