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United States Department of Agriculture

Agricultural Research Service

Research Project: GENOMICS AND ENGINEERING OF STRESS TOLERANT MICROBES FOR LOWER COST PRODUCTION OF ETHANOL FROM LIGNOCELLULOSE

Location: Bioenergy Research Unit

Title: Heat Shock Protein Genes and Newly Integrated Glucose Metabolic Pathways Promote Ethanol Tolerance of Saccharomyces cerevisiae

Authors
item Ma, Menggen -
item Liu, Zonglin

Submitted to: American Society for Microbiology Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: May 27, 2010
Publication Date: N/A

Technical Abstract: Lignocellulose-to-ethanol conversion provides a promising alternative means for production of sustainable and cleaner transportation fuels. Development of stress tolerant ethanologenic Saccharomyces cerevisiae is important for low-cost biobased economy. Tolerance to high levels of ethanol has been considered as one of the most desirable characteristics of ethanologenic yeast for yield improvement and cost reduction. Building upon our inhibitor-tolerant yeast, we generated ethanol-tolerant strain NRRL Y-50316 that is able to establish a culture on YM medium containing 8% ethanol and to complete fermentation reaching a higher concentration of ethanol at 96 g/L when provided with glucose at 100 g/L. Using a newly developed robust standard and master equation for unification of gene expression data analysis, we investigated transcriptional dynamics corresponding to metabolic profiling under the ethanol challenge for more than 170 genes based on previous microarray studies. In addition to those previously observed, we report new findings on expression of genes induced by the ethanol challenge, including HSP31, HSP32, HSP150, GSY2, ETR1, GCY1, IRC15, GND2, NQM1, SOL4, GRE2, TPO1, DDI1, PDR15, and YDR248C. Heat shock protein genes appeared to play a key role conferring the ethanol tolerance in yeast. Our results suggested that enriched transcription abundance and continued enhanced expression of these genes along with relevant genes of PDR family, glycolysis and pentose phosphate pathway, and trehalose metabolisms were critical for the ethanol-tolerant mutant to function against the ethanol stress. Consequently, reprogrammed glucose metabolic pathways in response to the ethanol challenge allowed a successful ethanol conversion by yeast. Yeast cell’s failure in pathway adaptation and expression of these genes under the stress were unable to establish a viable culture and complete ethanol fermentation. Our findings will guide metabolic engineering efforts for more tolerant strain development.

Last Modified: 10/24/2014