Engineering Microbial Consortia for High-Performance Cellulosic Hydrolyzates-Fed Microbial Fuel Cells

Feng Li; Xingjuan An; Deguang Wu; Jing Xu; Yuanyuan Chen; Wenchao Li; Yingxiu Cao; Xuewu Guo; Xue Lin; Congfa Li; Sixin Liu; Hao Song

doi:10.3389/fmicb.2019.00409

Engineering Microbial Consortia for High-Performance Cellulosic Hydrolyzates-Fed Microbial Fuel Cells

Front Microbiol. 2019 Mar 18:10:409. doi: 10.3389/fmicb.2019.00409. eCollection 2019.

Authors

Feng Li¹, Xingjuan An¹, Deguang Wu^{2

3}, Jing Xu¹, Yuanyuan Chen¹, Wenchao Li¹, Yingxiu Cao¹, Xuewu Guo³, Xue Lin⁴, Congfa Li⁴, Sixin Liu⁴, Hao Song¹

Affiliations

¹ Key Laboratory of Systems Bioengineering (MOE), Frontier Science Center for Synthetic Biology, School of Chemical Engineering and Technology, Tianjin University, Tianjin, China.
² Department of Brewing Engineering, Moutai Institute, Renhuai, China.
³ Tianjin Engineering Research Center of Microbial Metabolism and Fermentation Process Control, Tianjin University of Science and Technology, Tianjin, China.
⁴ College of Food Science and Technology, Hainan University, Haikou, China.

Abstract

Microbial fuel cells (MFCs) are eco-friendly bio-electrochemical reactors that use exoelectrogens as biocatalyst for electricity harvest from organic biomass, which could also be used as biosensors for long-term environmental monitoring. Glucose and xylose, as the primary ingredients from cellulose hydrolyzates, is an appealing substrate for MFC. Nevertheless, neither xylose nor glucose can be utilized as carbon source by well-studied exoelectrogens such as Shewanella oneidensis. In this study, to harvest the electricity by rapidly harnessing xylose and glucose from corn stalk hydrolysate, we herein firstly designed glucose and xylose co-fed engineered Klebsiella pneumoniae-S. oneidensis microbial consortium, in which K. pneumoniae as the fermenter converted glucose and xylose into lactate to feed the exoelectrogens (S. oneidensis). To produce more lactate in K. pneumoniae, we eliminated the ethanol and acetate pathway via deleting pta (phosphotransacetylase gene) and adhE (alcohol dehydrogenase gene) and further constructed a synthesis and delivery system through expressing ldhD (lactate dehydrogenase gene) and lldP (lactate transporter gene). To facilitate extracellular electron transfer (EET) of S. oneidensis, a biosynthetic flavins pathway from Bacillus subtilis was expressed in a highly hydrophobic S. oneidensis CP-S1, which not only improved direct-contacted EET via enhancing S. oneidensis adhesion to the carbon electrode but also accelerated the flavins-mediated EET via increasing flavins synthesis. Furthermore, we optimized the ratio of glucose and xylose concentration to provide a stable carbon source supply in MFCs for higher power density. The glucose and xylose co-fed MFC inoculated with the recombinant consortium generated a maximum power density of 104.7 ± 10.0 mW/m², which was 7.2-folds higher than that of the wild-type consortium (12.7 ± 8.0 mW/m²). Lastly, we used this synthetic microbial consortium in the corn straw hydrolyzates-fed MFC, obtaining a power density 23.5 ± 6.0 mW/m².

Keywords: Shewanella oneidensis; cellulosic hydrolyzates; microbial consortia; microbial fuel cell; synthetic biology.