title: Flocculating Zymomonas mobilis is a promising host to be engineered for fuel ethanol production from lignocellulosic biomass.
abstract: Whereas Saccharomyces cerevisiae uses the Embden-Meyerhof-Parnas pathway to metabolize glucose, Zymomonas mobilis uses the Entner-Doudoroff (ED) pathway. Employing the ED pathway, 50% less ATP is produced, which could lead to less biomass being accumulated during fermentation and an improved yield of ethanol. Moreover, Z. mobilis cells, which have a high specific surface area, consume glucose faster than S. cerevisiae, which could improve ethanol productivity. We performed ethanol fermentations using these two species under comparable conditions to validate these speculations. Increases of 3.5 and 3.3% in ethanol yield, and 58.1 and 77.8% in ethanol productivity, were observed in ethanol fermentations using Z. mobilis ZM4 in media containing ∼100 and 200 g/L glucose, respectively. Furthermore, ethanol fermentation bythe flocculating Z. mobilis ZM401 was explored. Although no significant difference was observed in ethanol yield and productivity, the flocculation of the bacterial species enabled biomass recovery by cost-effective sedimentation, instead of centrifugation with intensive capital investment and energy consumption. In addition, tolerance to inhibitory byproducts released during biomass pretreatment, particularly acetic acid and vanillin, was improved. These experimental results indicate that Z. mobilis, particularly its flocculating strain, is superior to S. cerevisiae as a host to be engineered for fuel ethanol production from lignocellulosic biomass.
authors.affiliation: School of Life Sciences and Biotechnology, Dalian University of Technology, Dalian, China.
authors.forename: Ning
authors.initials: N
authors.lastname: Zhao
authors.forename: Yun
authors.initials: Y
authors.lastname: Bai
authors.forename: Chen-Guang
authors.initials: CG
authors.lastname: Liu
authors.forename: Xin-Qing
authors.initials: XQ
authors.lastname: Zhao
authors.forename: Jian-Feng
authors.initials: JF
authors.lastname: Xu
authors.forename: Feng-Wu
authors.initials: FW
authors.lastname: Bai
mesh_terms: D000085:Acetates / Q000737:chemistry / Q000378:metabolism; D018533:Biomass; D000431:Ethanol / Q000138:chemical synthesis* / Q000378:metabolism; D005285:Fermentation; D005947:Glucose / Q000378:metabolism*; D006019:Glycolysis; D008031:Lignin / Q000737:chemistry / Q000378:metabolism; D017355:Zymomonas / Q000235:genetics* / Q000378:metabolism
chemical_list: D000085:Acetates; C036909:lignocellulose; D000431:Ethanol; D008031:Lignin; D005947:Glucose
keywords: Biofuels; Ethanol fermentation; White/industrial biotechnology; Yield; Zymomonas mobilis