Improvement Of A High Tolerance And High Ethanol Yield Of Saccharomyces Cerevisiae And Application In Industrial Hydrolysate

Fossil fuels depletion around the world and growing environmental concerns has led to the search for an alternative source of fuel.Bio-ethanol,which is environmentally friendly,is now highly sought for and recognized as one of the most promising renewable clean energy.Second-generation bio-ethanol using lignocelluloses as renewable biomass resources,but inhibitors produced during lignocelluloses hydrolyzing inhibit yeast growth and bio-ethanol production seriously hinder the bio-ethanol industrial development.Therefore,this article is based on a series of strain improvement methods,including UV irradiation,chemical mutagenesis,genome shuffling and evolutionary engineering,to improve strain STXQ's tolerance to biomass derived inhibitors and fermentation performance of industrial hydrolysate,finally obtain a strain which can utilize industrial hydrolysate to produce bio-ethanol.Initial strain STXQ displays superior fermentation performance which can simultaneously co-ferment 162g/L glucose and 95g/L xylose and generated 120.6g/L ethanol in 23h.However,it was not able to ferment industrial biomass hydrolysate due to inhibitions.Strain STXQ was mutated by UV irradiation and chemical mutagenesis,after screened we obtained a mutant 7#which can produce 8.91g/L ethanol,3.36 times of STXQ's production,in a medium with inhibitors?8g/L acetic acid and 1g/L furfural?;and co-ferment glucose and xylose to gain 45.38g/L ethanol,4.05 times of that of STXQ.Two rounds of adaptation in stringent nutrient limitation medium and industrial hydrolysate were conducted to the mutant 7#,followed by a series of screening to gain two potential strains ASTXQ and A₂STXQ,and texted industrial hydrolysate???fermentation performance.Strain ASTXQ was able to ferment 2-fold of industrial hydrolysate containing 80g/L glucose and 35.2g/L xylose and produced 48g/L ethanol with a yield of0.417 g gbiomass^-1 in 48h.Strain A₂STXQ could use up total sugars in a more toxic industrial hydrolysate????containing 27.6g/L glucose and 15.7g/L xylose?to generate13.8g/L ethanol within 48h.These results suggest that strains ASTXQ and A₂STXQ have great potential in industrial biomass hydrolysate fermentation and cellulosic ethanol production.