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| Construction of Saccharomyces cerevisiae Strains Improved Stress Tolerance and Ethanol Fermentation Performance through Metabolic Engineering and Genome Recombination |
| ZHANG Xiao-yang1, DU Feng-guang1, CHI Xiao-qin2, WANG Pin-mei2, ZHENG Dao-qiong2, WU Xue-chang2 |
1. State Key Laboratory of Motor Vehicle Biofuel Technolog, Tianguan Group Co., Ltd, Nanyang 473000, China;
2. Institute of Microbiology, College of Life Science, Zhejiang University, Hangzhou 310058, China |
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Abstract Some environmental stresses, i.e., high osmotic stress, fluctuating temperature and ethanol concentration, will greatly influence the viability and capability of the yeast S.cerevisiae strains during ethanol fermentation. In this study, we constructed a series of yeast strains with improved stress tolerances and ethanol fermentation performance through trehalose metabolism engineering combined with hybridization-based whole genome recombination. Firstly, two haploid strains , Z1 and Z2 isolated from the diploid strain Zd4, were engineered to enhance the intracellular trehalose by (1) overexpression of trehalose-6-phosphate synthase gene TPS1 (Z1ptps1 and Z2ptps1), (2) deletion of acidic trehalase gene ATH1 (Z1Δath1 and Z2Δath1), and (3) TPS1 overexpression combined with ATH1 deletion (Z1pTΔA and Z2pTΔA). We then obtained four recombination strains (Z12, Z12ptps1, Z12Δath1 and Z12 pTΔA) through the hybridization of Z1 and Z2, and their engineered strains. The results of high-gravity fermentation (270 g/L glucose) showed that TPS1 overexpression combined with ATH1 deletion had a distinct advantage in the improvement of stress tolerance over the single genetic manipulation. Compared to the original strain Zd4 and Z12, the strain Z12pTΔA(the hybrid of Z1pTΔA and Z2pTΔA) improved the fermentation rate by 11.4% and ethanol yield by 7.0%, while the strain Z12 without metabolic engineering only increased the main fermentation rate by 4.8% and ethanol yield by 2.8%. These improvements of fermentation performance consisted with their tolerances of the constructed strains under the conditions with osmotic pressure, high temperature and high concentration of ethanol. The combination of trehalose metabolic engineering and genome recombinant technology could effectively improve the stress tolerance and the ethanol fermentation performance of the industrial S.cerevisiae strains is demonstrated, and an innovative strategy for industrial yeast breeding is proposed.
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Received: 30 May 2011
Published: 25 July 2011
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