Engineering Saccharomyces Cerevisiae for Enhanced Ethanol Production via Overexpression of Alcohol Dehydrogenase Genes

• Zahraa Falah Azeez

  Collage of Biotechnology, University of Al-Qadisiyah, Iraq.

  Author

Saccharomyces cerevisiae is one of the most effective microorganisms in the fermentation process of producing bioethanol anaerobically. To come up with sustainable biofuel technology, it is important to improve its ethanol production. Our objective was to enhance the production of ethanol by overexpression of three important alcohol dehydrogenase genes (ADH1, ADH2, and ADH3) that code enzymes that catalyze the last stage in the synthesis of ethanol. Individual and clustered overexpressed ADH genes of S. cerevisiae were expressed as engineered strains of S. cerevisiae using the pRS426 plasmid system and grew under controlled fermentation. Gas chromatography (GC) and spectrophotometric analysis were used to measure the production of ethanol, the uptake of glucose and kinetics of growth. Findings indicated that the production of ethanol was highly increased in all the engineered strains as compared to the control group (BY4741). The strain that had high ethanol concentration (64.0 g/L) was obtained when it expresses the genes of ADH1, ADH2, and ADH3 concurrently, which is 42% more than the control strain (45.0 g/L). There was also an acceleration in glucose consumption, which was fully utilized within 60 hours and it means that there was better metabolic efficiency. A significant difference was found in the level of production of ethanol in the engineered strains as statistically determined (ANOVA, p < 0.001). Conclusion, ADH gene overexpression redirects the metabolic pathway in the production of ethanol with minimal byproducts. These findings demonstrate the possibility of focused metabolic engineering in the optimization of large scale cost-effective production of bioethanol by microbial systems.

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