Development Of Recombinant Industrial Strains Of Saccharomyces Cerevisiae With High Activity Of Decreasing Viscosity In Ethanol Production From Lignocellulosic Biomass

Cellulose,one of the most attractive alternatives to fossil fuels,can be degraded into fermentation reducing sugars which can be subsequently used for the production of biofuels and other useful chemicals.In the present context,profitable,abundant and renewable non-food lignocelluloses,such as corncob and bagasse,have been studied and used for industry.Saccharomyces cerevisiae,especialy industrial yeast,which is specialized for the utilization of its monosaccharide and disaccharide sucrose,can be cellulolytic by expressing a heterologous cellulase system.In order to be price-competitive,the productions of cellulosic ethanol still need technological improvements.In this study two endoglucanase(EG)genes were respectively integrated into delta regions of a derivative of the Angel Yeast strain.The recombinant strains,A129,T1,T2,T3 and T4 could hydrolysis carboxymethyl cellulose rapidly.The recombinant S.cerevisiae strains expressed better fermentation performance than their parent strains.When ethanol fermentation was performed with pretreated corncob,the recombinant industrial S.cerevisiae strain A129 produced 3.60% ethanol at 144 hour corresponding to the yield 85.7% with two commercial cellulases,IJT cellulase(10 FPU/g biomass)and NS 50010(5 U/g biomas),while the ethanol yield of its parent strain was 81.7%.When using pretreated sugarcane bagasse 77.1% ethanol yield was obtained by the recombinant A129 with double dosages of commercial cellulases,comparing to the ethanol yield of its parent strain was 71.7%.Therefore,the industrial S.cerevisiae strains integrated and expressing endoglucanase can be used as a cellulolytic platform for developing an economical advanced biofuel process.The recombinant industrial Saccharomyces cerevisiae integrated with endoglucanase and ?-glucosidase genes were engineered.Four positive clones,Angle BE1,Angle BE2,Angle BE3 and Angle BE4 were selected and their endoglucanase activities all reached 24 U/ml,and their ?-glucosidase activities were 0.46 U/ml,0.33 U/ml,0.66 U/ml and 0.64 U/ml at 48 h,respectively.When ethanol fermentation of Angle BE3 was performed with pretreated sugarcane bagasse using 20FPU/g biomass of IJT cellulose and 10 FPU/g biomass of IJT cellulose,3.52% and 3.42% ethanol were obtained,respectively.When ethanol fermentation of Angle BE3 was performed with pretreated corncob using 10 FPU/g biomass of IJT cellulose and 5 FPU/g biomass of IJT cellulose,3.57% and 2.86% ethanol were obtained,respectively.Thus,The industrial S.cerevisiae strains integrated and expressing endoglucanase and ?-glucosidase can be used for developing an economical advanced biofuel process to decrease the cost of the cellulose in the industrial production of cellulosic ethanol.