Expression of a xylose-specific transporter improves ethanol production by metabolically engineered Zymomonas mobilis

• Published in: Applied microbiology and biotechnology Vol. 98; no. 15; pp. 6897 - 6905
• Main Authors: Dunn, Kori L, Rao, Christopher V
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer-Verlag 01.08.2014; Springer Berlin Heidelberg; Springer; Springer Nature B.V
• Subjects: Alcohol; Alcohol, Denatured; Biodiesel fuels; Bioenergy and Biofuels; Biofuels; Biological Transport; Biomedical and Life Sciences; Biotechnology; Carbon; E coli; Efficiency; Escherichia coli; Escherichia coli - genetics; Escherichia coli Proteins - genetics; Escherichia coli Proteins - metabolism; Ethanol; Ethanol - metabolism; ethanol production; Ethyl alcohol; Fermentation; Gene Expression; Genetic aspects; Genetic engineering; Glucose; Glucose - metabolism; Life Sciences; Metabolic Engineering; Metabolism; Microbial Genetics and Genomics; Microbiology; Physiological aspects; Plasmids; Production data; Production processes; Proteobacteria; Species Specificity; Studies; Sugar; Sugars; Symporters - genetics; Symporters - metabolism; Transport; Transporter; Uptakes; Xylose; Xylose - metabolism; Yeast; Zymomonas - genetics; Zymomonas - metabolism; Zymomonas mobilis; United States > US; Xylose; Ethanol; Fermentation; Sugar transport
• ISSN: 0175-7598; 1432-0614
• DOI: 10.1007/s00253-014-5812-6

Zymomonas mobilis is a promising organism for biofuel production as it can produce ethanol from glucose at high rates. However, Z. mobilis does not natively ferment C5 sugars such as xylose. While it has been engineered to do so, the engineered strains do not metabolize these sugars at high rates. Previous research has identified some of the bottlenecks associated with xylose metabolism in Z. mobilis. In this work, we investigated transport as a possible bottleneck. In particular, we hypothesized that the slow uptake of xylose through the promiscuous Glf transporter may limit the efficiency of xylose metabolism in Z. mobilis. To test this hypothesis, we expressed XylE, the low-affinity xylose transporter from Escherichia coli, in a xylose-utilizing strain of Z. mobilis. Our results show that the expression of this pentose-specific transporter improves the rate of xylose utilization in Z. mobilis; however, this enhancement is seen only at high xylose concentrations. In addition, we also found that overexpression of the promiscuous Z. mobilis transporter Glf yielded similar results, suggesting that the transport bottleneck is not due to the specificity, but rather the capacity for sugar uptake.