Metabolic engineering of Zymomonas mobilis for 2,3-butanediol production from lignocellulosic biomass sugars.
BACKGROUND
To develop pathways for advanced biofuel production, and to understand the impact of host metabolism and environmental conditions on heterologous pathway engineering for economic advanced biofuels production from biomass, we seek to redirect the carbon flow of the model ethanologen Zymomonas mobilis to produce desirable hydrocarbon intermediate 2,3-butanediol (2,3-BDO). 2,3-BDO is a bulk chemical building block, and can be upgraded in high yields to gasoline, diesel, and jet fuel.


RESULTS
2,3-BDO biosynthesis pathways from various bacterial species were examined, which include three genes encoding acetolactate synthase, acetolactate decarboxylase, and butanediol dehydrogenase. Bioinformatics analysis was carried out to pinpoint potential bottlenecks for high 2,3-BDO production. Different combinations of 2,3-BDO biosynthesis metabolic pathways using genes from different bacterial species have been constructed. Our results demonstrated that carbon flux can be deviated from ethanol production into 2,3-BDO biosynthesis, and all three heterologous genes are essential to efficiently redirect pyruvate from ethanol production for high 2,3-BDO production in Z. mobilis. The down-selection of best gene combinations up to now enabled Z. mobilis to reach the 2,3-BDO production of more than 10 g/L from glucose and xylose, as well as mixed C6/C5 sugar streams derived from the deacetylation and mechanical refining process.


CONCLUSIONS
This study confirms the value of integrating bioinformatics analysis and systems biology data during metabolic engineering endeavors, provides guidance for value-added chemical production in Z. mobilis, and reveals the interactions between host metabolism, oxygen levels, and a heterologous 2,3-BDO biosynthesis pathway. Taken together, this work provides guidance for future metabolic engineering efforts aimed at boosting 2,3-BDO titer anaerobically.
National Bioenergy Center, National Renewable Energy Laboratory, Golden, 80401 USA ; Hubei Collaborative Innovation Center for Green Transformation of Bio-resources, Hubei Key Laboratory of Industrial Biotechnology, College of Life Sciences, Hubei University, Wuhan, 430062 China.
Shihui
0000-0002-9394-9148
S
Yang
National Bioenergy Center, National Renewable Energy Laboratory, Golden, 80401 USA.
Ali
A
Mohagheghi
National Bioenergy Center, National Renewable Energy Laboratory, Golden, 80401 USA.
Mary Ann
MA
Franden
National Bioenergy Center, National Renewable Energy Laboratory, Golden, 80401 USA.
Yat-Chen
YC
Chou
National Bioenergy Center, National Renewable Energy Laboratory, Golden, 80401 USA.
Xiaowen
X
Chen
National Bioenergy Center, National Renewable Energy Laboratory, Golden, 80401 USA.
Nancy
N
Dowe
Biosciences Center, National Renewable Energy Laboratory, Golden, CO 80401 USA.
Michael E
ME
Himmel
National Bioenergy Center, National Renewable Energy Laboratory, Golden, 80401 USA.
Min
M
Zhang
2,3-Butanediol; Advanced biofuel; Fermentation; Metabolic engineering; Omics; Redox balance; Respiration chain; Zymomonas mobilis