Genetics and metabolic engineering of yeast strains for efficient ethanol production

Bioethanol production from monomeric sugar is performed by several yeasts. But there are several limitations associated with yeast strains such as their low tolerance to ethanol, toxic inhibitors, and high sugar concentration. Genetic and metabolic engineering of potential yeast strains can overcome the above limitations. The present article summarized current genetic and metabolic engineering approaches for the development of yeast strain for efficient ethanol production. The review systematically examined bioethanol generations based on substrate utilization, criteria for strain selections, strategies for strain improvements including randomized mutagenesis, genetic engineering, metabolic engineering, genome editing, whole genome (re)sequencing, promoter engineering, quantitative trait locus analysis, protein engineering, and evolutionary engineering. Different fermentation technologies employed in hydrolysate fermentation including low gravity (LG), high gravity (HG), and very high gravity (VHG) as well as challenges of yeast strains development and its future prospect have been critically evaluated in this article. Significant engineering efforts are imminent for yeast-based second-generation biofuel to leave a demonstration phase through strain improvement and become economically competitive with fossil fuel. Practical Applications This is a comprehensive review of yeast strain development for bioethanol production. The readers should be able to acquire some basic knowledge on: The accompanied substrates for bioethanol generations as well as the technologies and challenges behind them. The criteria to consider in selecting yeast strain for bioengineering development. Different strategies and their reported applications employed in yeast strain development including randomized mutagenesis, genetic engineering, metabolic engineering, genome editing, whole genome (re)sequencing, promoter engineering, quantitative trait locus (QTL) analysis, protein engineering, and evolutionary engineering. Challenges and merits of different fermentation technologies employed in hydrolysate fermentation including LG, HG, and VHG. Possible challenges to encounter in developing yeast strain for bioethanol production. Desirable traits to consider in the selection and development of yeast strains for bioethanol production.