Researchers, Mekonnen M Demeke and group, at the Laboratory of Molecular Cell Biology, Leuven-Heverlee, and the Department of Molecular Microbiology, VIB in Belgium modified the genetic makeup of yeast strains through yeast mating. They developed not one but three strains of super-yeast that had both D-xylose conversion ability and high tolerance to inhibitors. The main strain, Ethanol Red, already has successful industrial application and the fact that these three super-strains are derived from it goes on to show that there will be no limitations to their industrial applications for synthesis of biofuel.
After screening 580 Saccharomyces cerevisiae (yeast) strains, researchers identified a strain with the highest tolerance to inhibitors. It was mated with an industrial yeast strain GS1.11-26 (having the genetic background of Ethanol Red) that could ferment D-xylose. From the resultant hybrids, two strains (GSF335 and GSF767) were selected that had had high inhibitor tolerance as well as D-xylose conversion ability. Separately, a third super-strain was produced through meiotic recombination. The result – three super strains exhibiting “significantly improved tolerance to inhibitors in spruce hydrolysate, higher glucose consumption rates, higher aerobic growth rates and higher maximal ethanol accumulation capacity in very-high gravity fermentation, compared to GS1.11-26”. Simply put, these strains had better D-xylose conversion capacity and inhibitor tolerance compared to the primary strain.
Engineering of traits for D-xylose conversion has been a very challenging proposition in industrial biotechnological research. Until now, methods such as evolutionary engineering and mutagenesis were attempted. However, researchers had little control over these processes. The development of yeast superstrain is thus a major breakthrough in this field. Further research on other such traits for the