Engineering Escherichia coli for succinate production from hemicellulose via consolidated bioprocessing

Microbial Cell Factories

Research

Zongbao Zheng¹  Zhiwen Wang¹  Meina Zhao¹  Tao Chen¹  Xueming Zhao¹ 

[1] Key Laboratory of Systems Bioengineering, Ministry of Education, Tianjin University, 300072, Tianjin, People's Republic of China;Department of Biochemical Engineering, School of Chemical Engineering and Technology, Tianjin University, 300072, Tianjin, People's Republic of China;

关键词: Consolidated bioprocessing;    Escherichia coli;    Hemicellulose;    Succinate;    Xylan;   

DOI  :  10.1186/1475-2859-11-37

 received in 2012-02-07, accepted in 2012-03-29,  发布年份 2012

来源: Springer

【 摘 要 】

BackgroundThe recalcitrant nature of hemicellulosic materials and the high cost in depolymerization are the primary obstacles preventing the use of xylan as feedstock for fuel and chemical production. Consolidated bioprocessing, incorporating enzyme-generating, biomass-degrading and bioproduct-producing capabilities into a single microorganism, could potentially avoid the cost of the dedicated enzyme generation in the process of xylan utilization. In this study, we engineered Escherichia coli strains capable of exporting three hemicellulases to the broth for the succinate production directly from beechwood xylan.ResultsXylanases were extracellular environment-directed by fusing with OsmY. Subsequently, twelve variant OsmY fused endoxylanase-xylosidase combinations were characterized and tested. The combination of XynC-A from Fibrobacter succinogenes S85 and XyloA from Fusarium graminearum which appeared to have optimal enzymatic properties was identified as the best choice for xylan hydrolysis (0.18 ± 0.01 g/l protein in the broth with endoxylanase activity of 12.14 ± 0.34 U/mg protein and xylosidase activity of 92 ± 3 mU/mg protein at 8 h after induction). Further improvements of hemicellulases secretion were investigated by lpp deletion, dsbA overexpression and expression level optimization. With co-expression of α-arabinofuranosidase, the engineered E. coli could hydrolyze beechwood xylan to pentose monosaccharides. The hemicellulolytic capacity was further integrated with a succinate-producing strain to demonstrate the production of succinate directly from xylan without externally supplied hydrolases and any other organic nutrient. The resulting E. coli Z6373 was able to produce 0.37 g/g succinate from xylan anaerobically equivalent to 76% of that from xylan acid hydrolysates.ConclusionsThis report represents a promising step towards the goal of hemicellulosic chemical production. This engineered E. coli expressing and secreting three hemicellulases demonstrated a considerable succinate production on the released monosaccharides from xylan. The ability to use lower-cost crude feedstock will make biological succinate production more economically attractive.

【 授权许可】

Unknown   
© Zheng et al; licensee BioMed Central Ltd. 2012. This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.