Zymomonas mobilis: a novel platform for future biorefineries

Abstract

Biosynthesis of liquid fuels and biomass-based building block chemicals from microorganisms have been regarded as a competitive alternative route to traditional. Zymomonas mobilis possesses a number of desirable characteristics for its special Entner-Doudoroff pathway, which makes it an ideal platform for both metabolic engineering and commercial-scale production of desirable bio-products as the same as Escherichia coli and Saccharomyces cerevisiae based on consideration of future biomass biorefinery. Z. mobilis has been studied extensively on both fundamental and applied level, which will provide a basis for industrial biotechnology in the future. Furthermore, metabolic engineering of Z. mobilis for enhancing bio-ethanol production from biomass resources has been significantly promoted by different methods (i.e. mutagenesis, adaptive laboratory evolution, specific gene knock-out, and metabolic engineering). In addition, the feasibility of representative metabolites, i.e. sorbitol, bionic acid, levan, succinic acid, isobutanol, and isobutanol produced by Z. mobilis and the strategies for strain improvements are also discussed or highlighted in this paper. Moreover, this review will present some guidelines for future developments in the bio-based chemical production using Z. mobilis as a novel industrial platform for future biofineries.

Keywords: Zymomonas mobilis; biofuel; biorefinery; building block chemical; platform.

Figure 1

Selected milestones in Z. mobilis research.

Figure 2

Research history of recombinant Z. mobilis for ethanol production.

Figure 3

Reaction scheme for the production of bionic acid and sorbitol via glucose-fructose oxidoreductase (GFOR) and glucono-σ-lactonase(GL) of Z. mobilis.

Figure 4

Metabolic pathways for the production of the high-value products by using Z. mobilis as platform. The solid lines indicate Z. mobilis native pathways and the dotted lines refer to the recombinant pathway obtained by metabolic engineering strategies. gfor, glucose-fructose oxidoreductase; ldhA, lactate dehydrogenase; pdc, pyruvate decarboxylase; gnl, glucono-σ-gluconase; adc, acetoacetate dehydrogenase; adh, secondary alcohol dehydrogenase; adhB, alcohol dehydrogenase; adhE, acetaldehyde/alcohol dehydrogenase; adhE2, secondary alcohol dehydrogenase; atoAD, acetyl-CoA:acetoacetyl-CoA transferase; atoB, acetyl-CoA acyltransferase; bcd, butyryl-CoA dehydrogenase; crt, crotonase; ctfAB, acetoacetyl-CoA transferase; etfBA, electrotransfer flavor protein; hbd, β-hydroxy butyryl-CoA dehydrogenase; thl, acetyl-CoA acyltransferase; kivd, ketoisovalerate decarboxylase.

Figure 5

General process of fuel or chemical production by Z. mobilis .