纤维质酒精发酵的菌种选育及发酵条件的研究

【作者】 任立伟；

【导师】 陈光；

【作者基本信息】 吉林农业大学 ， 生物物理学， 2003， 硕士

【摘要】 本文研究了酿酒酵母(Saccharomyces cercvisiaeYT318)发酵纤维素物质(以玉米秸秆为原料)转化为燃料酒精的工艺过程，通过紫外线诱变法选育高产菌株YT318。YT318菌株与出发菌株YT18相比，产酒精能力提高了15％，发酵周期缩短了12小时。利用蒸汽爆破法对纤维质原料预处理其优化条件为：压力为1.2MPa，持压时间5min，总转化率为67.72％。从而建立了一种预处理原料对后期发酵作用效应的快速分析方法。 本文还对后期酒精发酵过程及营养因子进行了系统研究发现YT318对木糖、葡萄糖有较强的酒精发酵力。过高的糖浓度，有毒的物质，温度，酸度等都能够成为抑制发酵的因素。这些因素有些是在发酵前期起作用，如底物抑制作用和过高的酸度，有些则在发酵后期影响发酵的进行，如酒精和二氧化碳，及有机酸的抑制作用。值得注意的是本文讨论的各个因素的协同作用对发酵的抑制作用更强。 在发酵初期高于10％的总糖会产生抑制作用。因此发酵醪中低水平的底物浓度有利于酒精产量提高。采用分批补料的供糖方式的发酵可将原料利用率从82.62％提高到88.51％。因此在发酵初期底物抑制作用比发酵后期酒精的毒性作用要大。氮源的添加有利于酒精的生产。同样发酵条件下，添加氮源可以将发酵时间大幅度缩短。尿素是最佳的无机氮源，由于酵母细胞对氮源吸收利用特点，在发酵初期氮源需要保持较高水平。氧气有利于细胞生长和存活因子的生产，因此在发酵过程中保持一定量的分子氧对发酵有促进作用。 YT318菌株作为最佳工艺发酵菌对经预处理的玉米秸杆，最适发酵工艺条件：温度35℃，最佳摇床转速，100r/min，最适pH为5.5，经过60小时发酵，酒精浓度可达5.5V/V，残总糖在0.7％以下。表明该菌种对于实现纤维质原料酒精发酵是可行的。更多还原

【Abstract】 This paper studied the technological process of fermenting cellulose to fuel ethanol by saccharomyces cercvisiae YT318 which was obtained through UV mutation. Comparing to original Saccharotnycete YT18, YT318 increased in ethanol production capacity by 15% and decreased in fermentation with 12h. The optimized conditions of preparing cellulose with vapour-exploding was: pressure at 1.2 Mpa, time 5 min, productivity 67.72%.Systematic research on later part of alcohol fermentation and nutrient factors was conducted. It found that YT318 had great capability of alcohol-production on glucose and xylose. Excessive glucose density, toxious material, temperature, acid and so on could inhibit fermentation. Some factors took effect in earlier part of fermentation, while others in latter part. But the synergetic effects of these factors inhibited fermentation even more.Earlier part of fermentation were inhibited at 10% total sugar concentration. Low substrate density was beneficial to improvement of ethanol output. Utilization ratio on raw material could increase from 82.62% to 88.51% in fed-batch fermentation. So it showed substrate inhibition in earlier part of fermentation took more effect that alcohol toxicity in latter part of fermentation.Adding of nitrogen source helped produce alcohol and would shorten fermentation period. Area was the best inorganic nitrogen source which should maintain at high concentration at earlier part of fermentation because of saccharomycete’s feature.Oxygen was beneficial to cell growth and living factors production. It would enhance the fermentation if fixed amount of oxygen was maintained.As the best saccharomycete to prepared corn stalk, YT318 had a suitable cultureconditions: temperature 35℃, flaker speed l00r/min, pH 5.5. Ethanol concentration reached 5.5 V/V after 60 h’s fermentation and residual sugar was under 0.7%. This demonstrated that it was feasible to produce alcohol in fermentation on cellulose with YT318.更多还原