Research
Improved xylose and arabinose utilization by an industrial recombinant Saccharomyces cerevisiae strain using evolutionary engineering
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* Corresponding author: Marie F Gorwa-Grauslund Marie-Francoise.Gorwa@tmb.lth.se
1 Department of Applied Microbiology, Lund University, PO Box 124, SE-22100 Lund, Sweden
2 Center for Microbial Biotechnology, Department of Systems Biology, Technical University of Denmark, Soltofts plads, 2800 Kgs Lyngby, Denmark
3 Centro de Recursos Microbiológicos (CREM), Departamento de Ciências da Vida, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516 Caparica, Portugal
4 Laboratório Nacional de Energia e Geologia, I.P., Unidade de Bioenergia, Estrada do Paço do Lumiar 22, 1649-038, Lisboa, Portugal
5 Carlsberg Research Center, Gamle Carlsberg vej 10, DK-2500 Valby, Denmark
6 Department of Chemistry, Biotechnology and Food Science Norwegian University of Life Sciences, PO Box 5003, N-1432 Ås, Norway
Biotechnology for Biofuels 2010, 3:13 doi:10.1186/1754-6834-3-13
Published: 15 June 2010Abstract
Background
Cost-effective fermentation of lignocellulosic hydrolysate to ethanol by Saccharomyces cerevisiae requires efficient mixed sugar utilization. Notably, the rate and yield of xylose and arabinose co-fermentation to ethanol must be enhanced.
Results
Evolutionary engineering was used to improve the simultaneous conversion of xylose and arabinose to ethanol in a recombinant industrial Saccharomyces cerevisiae strain carrying the heterologous genes for xylose and arabinose utilization pathways integrated in the genome. The evolved strain TMB3130 displayed an increased consumption rate of xylose and arabinose under aerobic and anaerobic conditions. Improved anaerobic ethanol production was achieved at the expense of xylitol and glycerol but arabinose was almost stoichiometrically converted to arabitol. Further characterization of the strain indicated that the selection pressure during prolonged continuous culture in xylose and arabinose medium resulted in the improved transport of xylose and arabinose as well as increased levels of the enzymes from the introduced fungal xylose pathway. No mutation was found in any of the genes from the pentose converting pathways.
Conclusion
To the best of our knowledge, this is the first report that characterizes the molecular mechanisms for improved mixed-pentose utilization obtained by evolutionary engineering of a recombinant S. cerevisiae strain. Increased transport of pentoses and increased activities of xylose converting enzymes contributed to the improved phenotype.