Researchers are motivated into the development of alternative renewable energy sources, bioethanol being the most promising one, due to increasing demand of energy and limited supply of fossil fuel. Saccharomyces cerevisiae is frequently used for fermenting grains and carbohydrate rich substrates, referred as the carbohydrate based ethanol production with carbon neutral approach. The second generation biofuel production has also mitigated the use of feedstock as substrate for ethanol production. High amount of pentose sugars present in lignocellulosic hydrolysates and the unavailability of efficient organism to convert pentoses to ethanol has led the recombinant DNA technology to come into action for production of biofuel. Wild strains of S. cerevisiae ferments bio – available sugars such as glucose to produce ethanol, however, the production is limited by the organisms’ ability to transport and metabolize other sugar substrates such as xylose. GXS1 and GXF1 are the glucose/xylose symporter and glucose/xylose facilitator genes from Candida intermedia. Thus, S. cerevisiae is genetically engineered with these genes of interest to induce higher efficiency in terms of ethanol production. Previous studies with individual transformation of S. cerevisiae with GXS1 and GXF1 showed significant uptake of xylose from the medium with only slight increase in ethanol production, which could be attributed to the inability of the yeast to metabolize xylose. For this purpose, a synthetic gene, Xylose isomerase has been purchased and being currently cloned into yeast integrative plasmid. Further work in the pipeline would be to generate recombinant yeast with GXS1/GXF1 genes along with the Xylose isomerase gene. These genes transformed into S. cereviseae in combination, could lead to increase in efficiency of ethanol production along with xylose uptake.
