Studies On The Screening And Fermenting Characteristics Of Yeast Fermenting Xylose For Production Alcohol

Xylose is the main component of the fiber material,the amount of which is only less than that of glucose. CelluLose is the most abundant and cheap renewable resources on the earth, and it can be used to produce ethanol, which can not only reduce the cost, ease the food crisis, but also have important significance to improve the environment. Nowdays the topical research is celluLose converting into ethanol by microorganism, the crucial of which is the effective utilization of xylose. Using celluLosic as the raw material, the key of hydrolyzing and converting xylose to produce ethanol is the selection of effective strains.In this paper, we studied the isolation、identification and fermentation characteristics of D-Xylose-Fermenting yeasts. The reseach mainly has three aspects:(1) Isolating yeast strains from special environment. Yeast strains, which ferment xylose to produce ethanol, mianly live the abundence of xylose environment. Hence, the yeast strains mianly are isolated from insect feces, the insect eating or living woodiness. This experiment from May to September in 2014 successively in different parts of the Nanyang mountain collected 207 samples, from which separated and purified the 388 yeast strains by the dilution plate method. By Duchenne tube fermentation experiments, only 47 strains of the 388 yeast strains can ferminant xylose and produce ethanol.(2) Identification the yeast strains by molecuLar biology and morphophysiology. The process includes extracting DNA from the yeast strains, amplifing different sequences of the yeast strains(26s rDNA D1/D2、ITS、XYL1 sequences) by PCR method, and sequencing the PCR produces. Then, Comparisons with sequences from the international GenBank database were done using BLASTN search. After constructing phylogenetic tree, we identify the yeast strains by phylogenetic analyses and morphophysiology. Eventually, the 5 new strains were identified: Scheffersomyces sp. NYNU 14712T、Candida sp. NYNU 1488T、Spathaspora sp. NYNU 1495T、Candida sp. NYNU 14914T、Candida sp. NYNU 14959 T.(3) Research of ethanol fermentation characteristics using xylose. The 5 new strains had been studied glucose、xylose、and the mixture fermentation performance. Under the same fermentation condition, the 2 strians, Candida sp. NYNU 14914T、Candida sp. NYNU 14959 T, have good fermentation performance.The research provieds gene resources for improvig strains, which ferment xylose, by genetic engineering, and supply strain resources for cu Ltivating the fine yeast by directional breeding technology, further offer certain work foundation for improving strains, and provide some experimental basis to make full use of celluLosic materials to produce ethanol so as to realize industrialized production.