Establishment Of Evaluation System For Vitality Test Of Industrial Yeast Strains For Ethanol Fermentation And Its Application In High Vitality Culture

The quality of yeast is one of the most important factors in fermentation process for ethanol production. It is known that there are many factors, such as the different strains, inoculum sizes, and oxygen, temperature and pressure conditions, which have effects on yeast vitality. And it has been a focus research to establish an accurate and rapid evaluation system for vitality test of industrial yeast strains for ethanol fermentation in the world for years. Moreover, the cultivation of yeast directly affects on the fermentation course and fermentation intensity for ethanol production, especialy in the barren broth, followed by economic efficiency of ethanol plants being delined. Hence, it is meaningful to found and incubate the yeast with high activity accurately and timely in the alcohol production. The research methods and results are as follows:1. Three different methods were used to evaluate the vitality of beer yeast. It was found that these methods were not all adapt to evaluate the yeast strains'vitality for industrial ethanol production, and it could be concluded that different yeasts had different characteristics. Among these three methods, only the acidification power test could judging the yeast strains'vitality for industrial ethanol production exactly. Moreover, this method was conducted by routine experiment equipments and was simple operation and time-saving: Entire process was completed in 35 minutes, which could estimate the vitality of industrial yeast strains for ethanol fermentation in time.2. The optimum condition for the acidification power test was(w/w): mud yeast 10%, glucose 5%, 25°C. Under this condition , GIPE value was stable and significant.3. The coefficient of correlation between GIPE value and the yeast's ethanol production capacity was 0.8406, indicating that the acidification power and the yeast's ethanol production capacity had good correlativity. So the acidification power test could be used for evaluating yeast's fermentation ability.4. The results showed that when some ions such as Na+ (0.005 mol/L ), K+ (0.05 mol/L) , Mg2+ (0.002 mol/L) , Ca2+ (0.005 mol/L) was added to the medium, industry alcohol yeast vitality were 5.47, 10.17, 7.81 and 4.59 percent higher than incubated in the blank culture media without ions, respectively.5. Changes of parameters related to the physiological metabolism of the industrial yeast strains for ethanol fermentation showed that, the yeast vitality in the culture medium including four kinds commixture ions was maximal, 35.61 percent higher than incubated in the blank, and could maintain high vitality state for a long time,which indicated that these 4 kinds of ions in the yeast media having the role of intercoordination and mutual promotion .6. The optimum conditions for high vitality of the industrial yeast strains for ethanol fermentation were found by experiment, and the results were: saccharification period 40min, urea 0.25%(w/w), potassium ion 0.005 mol/L, calcium ion 0.002 mol/L. Under the optimum culture conditions, the starch utilization ratio has increased 2.73%. According to the results of alcohol fermentation test, fermentation ability of yeast not only related to the vitality of yeast but also the numbers of yeast. So, in order to improve the fermentation efficiency, the cultivation of yeast should be high vitality and high cell numbers.