Breeding Of Yeast High Producing Ethanol And Fermentation Condition With Dynamics

As increasingly exhausting of petroleum energy, Scientists in many countries begin to study to produce bioethanol from biomass. In this aspect, our country reseaches is mainly focus on producing.bioethanol with corn. However, it may results in potential crisis on food provision that using lots of corn to produce.bioethanol, as corn is the main food crop in our country. It is becoming an important and urgent task for our country to make use of nonfood biomass for ethanol production. Producing bioethanol from sugar cane can fetch up the shortage of food as stuff and the successful experience of Brazil'cane bioethanol has proved that sugar cane is perfect material for ethanol production In this paper,There are five findings were ascribed as follows: the identification of 18rRNA of the yeast stain YS₅, the breeding of high-ethanol-yield yeast, the study of physiology and biochemistry on the mutant YS_5-1, the optimization of fermentation condition and the research of ethahol fermentation dynamics.First, the 18rRNA sequence of the yeast strain YS₅ was cloned and identified, and then system evolution tree was constructed. Then yeast YS₅ as original strain was lysated by snail enzyme to prepare protoplast and was mutated by UV-irradiation. A high-ethanol-yield mutant YS_5-1 was obtained with regenerated by two cycles of screening. Its ethanol yield could reach 10.4% (v/v) , 8.6% higher than that of the original strain while the rate of sugar transformation reach 94.5%. After 5 generations of continual cultivation, the ethanol yield kept stable. In further Studying of YS_5-1 physiology and biochemistry, we found that its the most suitable growth temperature was 30℃,while the most suitable pH was 5.0. In the aspect of tolerance ,it seems more tolerant than yeast YS₅ in high ethanol degree, salt concentrate and glucose concentrate. Third, we optimized the fermentation technics with uniformity desire soft and determined the best optimizational conditions in producing bioethanol with cane liquor as follows: fermentation medium: sugar degree 17BX, yeast extract 1.1%, NH₄SO₄ 0.9%, KH₄PO₄ 0.4%, MgSO₄ 0.37; fermentation condition: pH4.4, inocuLation 6%, temperature 30℃,168h, the alconol yield was 11.3%(v/v).Finally, we adoped the intermittent ethanol fermentation with 7L fermentator and detected the growth of cell, consumption of sugar and the content of ethanol from the zymotic fluid in different time. Based on the logistic equation and Luedeking-Piret equation, different ethahol fermentation dynamics model on growth of cell,consumption of sugar and the content of ethanol was founded. The model could well reflect the changing pattern in growth of cell, residue sugar, and ethanol yield, which has guiding meaning for the actuaL ethanol production.