Screening Of Strain Decomposing Inhibitors,Highly Producing Ethanol From The Lignocellulose Acid Hydrolysates And Its Fermentation Characters

Lignocellulosic biomass, a low-cost renewable resource including forestry waste, agricultural residues and municipal solid waste, can be potentially fermented into ethanol by microbial technology that would fulfill increasing demand in fuel. Lignocellulose-derived ethanol is an environmentally friendly liquid fuel, because exhausted carbon dioxide is taken up through growing biomass and therefore makes no net contribution to the atmosphere.The study of screening the high efficiency ethanol-production-yeast tolerating/decomposing inhibitors take very important role on acceleration the industrialization of bio-ethanol, including establishment of ethanol-production new genus characteristics in eukaryote groups.By the way of optimized screening, a highly decomposing inhibitors of yeast strains YZ1 and YZ2 from the sludge. To further differentiate YZ1 and YZ2,the genes of 26S rDNA D1/D2 were amplified in vitro and sequenced,Then a phylogenetic dendrogram was constructed by comparing these two sequences with others.YZ1 and YZ2 can successfully ferment dilute-acid hydrolysate in bath mode.We have discussed the factors that can affect the ethanol-producing ability of YZ1 and YZ2 for hydrolysates of dilute-acid lignocellulose in the batch mode without any detoxification. The factors: methods of dealling with dilute-acid hydrolysate, residues and precipitation in adjusting PH of dilute-acid hydrolysate, oxygen, furfural and other inhibitors. Ethanol concentration of 19.8 g/L and a yield of 0.40g/g were obtained with the bath fermentation of the hydrolysate by YZ2,the total sugar conversion efficiency were 80%.When furfural reach 3.3 g/L in Dilute-Acid Wood Hydrolysate, ethanol yield of YZ1 and YZ2 is 11.7 g/L, biomass can reach 5×10~7cell/ml.To study the fermentation condition of xylitol production by YZ1.An optimal fermentation method for shaken flask culture was achieved by altering culture conditions, such as the initial xylose concentration, aeration, nitrogen source and pH value. The optimal culture medium compositionwas as follows: initial xylose concentration 50 g/L, rotation speed 150 r/min, pH4.5.Under this condition,the highest xylitol yield was 0.61 g/g.