Construction of a Efficient Xylose Metabolic Pathway in Saccharomyces Cerevisiae for Ethanol Production

Yun-Jie Li, Tian-Wei Tan*

Beijing Key Lab of Bioprocess, College of Life Science and Technology, Beijing University of Chemical Technology, Beijing 100029, People’s Republic of China

E-mail: liyunjie2012@gmail.com or twtan@mail.buct.edu.cn

Abstract

Nowadays the low ethanol yield and productivity of xylose from plant biomass by saccharomyces cerevisiae is a big problem, so that it seriously hinders the development of industrial cellulose bioethanol. To overcome this bottleneck, we introduced two key genes of Calvin-Cycle to improve the non-oxidative phase of the pentose phosphate pathways(PPP), which is the necessary steps of xylose metabolism. In the engineered S.cerevisiae, we expressed codon-optimized phosphoribulokinase (PRK) , and ribulose-1,5-biphosphate carboxylase/oxygenase (Rubisco) from Ralstonia eutropha H16, and codon-optimized GroEL/GroES from Escherichia coli, coupled with the overexpression of mutant XYL1(R276H) and XYL2 from Scheffersomyces stipitis and XKS from S.cerevisiae. We observed improved ethanol yield (0.45 g/g) and productivity (0.79 g/L/h) from cofermentation experiments performed with glucose (80g/L )and xylose (50g/L), suggesting this is a promising glucose and xylose metabolic strategy for cellulose biofuel production. The successful integration shortened PPP in S.cerevisiae is a critical step towards enabling economic biofuel production.