Screening Of Yeast Species For High Alcohol Yield And Their Phylogenetic Analysis Of RDNA ITS Sequence

The yeasts, which spread extremely widely around the surface of the earth, is one part of fungus with high economic value. The overwhelming of them are saprophytes. They play an important role in the bioindustry. People are greatly interested in yeasts for its strong power of fermentation. They can turn carbohydrate into ethanol and CO₂ through the process of biotransformation. Therefore, they are applied widely in the fermentative industy, particularly the species Saccharomyces cerevisiae. However, the strains from different origins have many differences in the some aspects including heat resistant, ethanol tolerance, the fermentative ability to produce ethanol by producing different medium and so on. Presently, with the fossil resources reducing day by day, it is becoming more important to deeply exploit yeasts'productive potential in the biotransformation ethanol industry. Yeasts' preponderant productive ability could not be separated from the status of phylogenetic development and the shape evolution in the fungus Kingdom. The shape of yeast is simple, and its shape data used in classification is inadequate. In fact, the classification of species mainly depend on physiology biochemistry characteristic. With the development of molecular biology, this technology is applied broadly in the fungus system analysis. The rDNA ITS evolve most quickely so that it may reflect the changes in the real mold mushroom spawn or in the group. This paper is to make studies on yeasts with different physiological characteristics from different origins through the analysis of rDNA ITS sequence in phylogenetics. Moreover, the yeast strains which were separated in the fermentation were screened at different levels on the ability of producing ethanol. The research is divided into two parts as following:1. The screening of high productive yeast strain to produce ethanolThis part is for the purpose of screening the separated yeast strains at different levels on the ability of ethanol production so that it can provide the basic research background for its patato-based industrialized production.2. Phylogenetic analysis of yeastThis part is to analyze yeasts'phylogenesis. During this experiment, the rDNA ITS of 21 isolate strains with differenct physiological characteristics from different origins and 4 type strains, has been amplified and sequenced through the nucleic acid sequence analysis method. The results from the systems analysis indicate that 9 isolate strains are identified on species level, 9 on genera level, and the left 3 strains are hard identified on genera level. Meanwhile, the relationship among the tested strains and their phylogeny are analyzed by phylogenesis tree.