Enhancement of D-lactic acid production from a mixed glucose and xylose substrate by the Escherichia coli strain JH15 devoid of the glucose effect

BMC Biotechnology

Research Article

Ryan Manow¹  Erin Garza¹  Andrew Iverson²  Hongying Lu³  Yongze Wang³  Xiaoren Ding³  Xiao Zhao³  Jinhua Wang³  Shengde Zhou⁴ 

[1] Department of Biological Sciences, Northern Illinois University, 60115, DeKalb, IL, USA;Department of Biological Sciences, Northern Illinois University, 60115, DeKalb, IL, USA;William Rainey Harper College, 60142, Palatine, IL, USA;Hubei Provincial Cooperative Innovation Center of Industrial Fermentation, Key Laboratory of Fermentation Engineering (Ministry of Education), College of Bioengineering, Hubei University of Technology, 430068, Wuhan, P. R. China;Hubei Provincial Cooperative Innovation Center of Industrial Fermentation, Key Laboratory of Fermentation Engineering (Ministry of Education), College of Bioengineering, Hubei University of Technology, 430068, Wuhan, P. R. China;Department of Biological Sciences, Northern Illinois University, 60115, DeKalb, IL, USA;

关键词: Catabolite repression;    D-lactic acid;    E. coli;    Glucose effect;    ptsG;    PLA;    Xylose fermentation;   

DOI  :  10.1186/s12896-016-0248-y

 received in 2015-11-12, accepted in 2016-02-09,  发布年份 2016

来源: Springer

【 摘 要 】

BackgroundA thermal tolerant stereo-complex poly-lactic acid (SC-PLA) can be made by mixing Poly-D-lactic acid (PDLA) and poly-L-lactic acid (PLLA) at a defined ratio. This environmentally friendly biodegradable polymer could replace traditional recalcitrant petroleum-based plastics. To achieve this goal, however, it is imperative to produce optically pure lactic acid isomers using a cost-effective substrate such as cellulosic biomass. The roadblock of this process is that: 1) xylose derived from cellulosic biomass is un-fermentable by most lactic acid bacteria; 2) the glucose effect results in delayed and incomplete xylose fermentation. An alternative strain devoid of the glucose effect is needed to co-utilize both glucose and xylose for improved D-lactic acid production using a cellulosic biomass substrate.ResultsA previously engineered L-lactic acid Escherichia coli strain, WL204 (ΔfrdBC ΔldhA ΔackA ΔpflB ΔpdhR ::pflBp6-acEF-lpd ΔmgsA ΔadhE, ΔldhA::ldhL), was reengineered for production of D-lactic acid, by replacing the recombinant L-lactate dehydrogenase gene (ldhL) with a D-lactate dehydrogenase gene (ldhA). The glucose effect (catabolite repression) of the resulting strain, JH13, was eliminated by deletion of the ptsG gene which encodes for IIBCglc (a PTS enzyme for glucose transport). The derived strain, JH14, was metabolically evolved through serial transfers in screw-cap tubes containing glucose. The evolved strain, JH15, regained improved anaerobic cell growth using glucose. In fermentations using a mixture of glucose (50 g L−1) and xylose (50 g L−1), JH15 co-utilized both glucose and xylose, achieving an average sugar consumption rate of 1.04 g L−1h−1, a D-lactic acid titer of 83 g L−1, and a productivity of 0.86 g L−1 h−1. This result represents a 46 % improved sugar consumption rate, a 26 % increased D-lactic acid titer, and a 48 % enhanced productivity, compared to that achieved by JH13.ConclusionsThese results demonstrated that JH15 has the potential for fermentative production of D-lactic acid using cellulosic biomass derived substrates, which contain a mixture of C6 and C5 sugars.

【 授权许可】

CC BY   
© Lu et al. 2016