【作者】 王利民；

【导师】 庞宗文；

【作者基本信息】 广西大学 ， 发酵工程， 2007， 硕士

【摘要】 酒精是一种应用十分广泛、在国民经济中占有重要地位的工业产品。目前，发酵法生产酒精的菌种主要以酵母属的酿酒酵母菌为主，这些菌株基本不能利用木糖进行酒精发酵。本实验室从果园土壤筛选到一株能利用木糖进行酒精发酵的热带假丝酵母XY-3。本实验通过对XY-3生长和发酵性能的研究，并与酒精工业生产菌株4608进行比较发现：XY-3不仅生长快、耐高温（45℃）、耐酸（pH2.0）、耐糖（40％葡萄糖），而且能利用木糖进行酒精发酵，但其缺点是酒精的耐受能力差、发酵液酒精含量低、残糖量高。同时，我们也得到XY-3的最适生长条件：最适生长温度为35℃左右、最适生长pH值为7.0左右；最适发酵条件：最适发酵温度为32℃左右、最适发酵初始pH值为4.0左右，最适发酵时间为48h。本实验通过对热带假丝酵母XY-3进行紫外线诱变，选育得到5株耐酒精能力提高的菌株，其中UV-72比出发菌株XY-3提高了88.4％；经Co⁶⁰-γ射线诱变后，选育得到的10株耐酒精能力提高的菌株，其中Co-167比XY-3提高了1.7倍左右；经过6轮基因组改组，选育得到32株耐酒精能力提高的菌株，其中G-3-47比对照菌株Co-167提高了69.5％，G-4-15比对照菌株G-2-40耐酒精能力提高了32.8％。经多次传代培养后发现，只有G-4-15和G-5-46的稳定性较好，酒精耐受能力分别提高了78.4％和86.4％。因此，用基因组改组技术提高酵母的耐酒精性能是一种可行的方法。选育得到的菌株虽然对酒精的耐受性有了很大提高，但实验发现其酒精的产生能力并没有提高。具体原因还有待进一步研究。更多还原

【Abstract】 Alcohol is an important industrial product which is used widely and plays an important role in the whole economy. Presently, the strain of alcohol product by fermentation is mainly Saccharomyces cerevisiae of Saccharomycetace, and they can not make use of xylose to product alcohol basically.Our laboratory has screened a Candida tropicalis XY-3 which can make use of xylose to ferment alcohol. Through the studies of growth and fermenting performance to XY-3, and in contrast to 4608 which is dominant strain in alcohol industrial production fermentation,we find that XY-3 not only grow fast, tolerate to high temperature（45°C）, to strong acid（pH2. 0） and high sugar （40% glucose）, but also can make use of xylose to ferment alcohol. The deficiencies are lower alcoholic tolerance, lower alcoholicity and higher residual sugar. At the same time, we also get the optimal growth conditions: optimal growth temperature is about 35°C, optimal growth pH is about 7.0; optimal fermentation conditions: optimal fermentation temperature is about 32°C, optimal fermentation initial pH is about 4.0, optimal fermentation time is 48h.The experiment breeded 5 strains which had higher alcoholtolerance by UV mutation to Candida tropical is XY-3, in which thealcohol tolerance of UV-72 had improved by 88. 4% compared to initialstrain XY-3;through the mutation of Co⁶⁰-γ, we breeded 10 strainswhich had higher alcohol tolerance, in which the alcohol toleranceof Co-167 had improved about 1.7 times compared to XY-3; Throughgenome shuffling of six rounds, we breeded 32 strains which had higheralcohol tolerance, in which the alcohol tolerance of G-3-47 hadimproved by 69. 5% compared to contrasting strain Co-167, G—4-15 hadimproved by 32.8%. compared to contrasting strain G-2-40. By meansof multiple subculture, we only found that the stabilities of G-4-15and G-5-46 are much better, the alcohol tolerance improved by 78.4%and 86.4% respectively. Therefore, the improvement of alcoholtolerance of yeasts by Genome shuffling is feasible.The breeded strains have a good improvement to alcohol tolerance, but we find that the ability of alcohol production is not improved. The concrete reasons need to further studies on.更多还原