PDF《博士学位论文》

48 g/L 和61%. 实验表明, S. cerevisiae DQ1 能够在高温下发酵纤维素基质生产乙醇;

高温乙醇发酵的微生物要在 高温下有强的生长能力和耐受性,而且必须在真实纤维素基质和发酵条件下检验.本研 究的创新在于使用耐高温的酿酒酵母 S. cerevisiae DQ1,在高固含量下同步糖化与发酵 真实的纤维素基质原料生产乙醇. 第三部分报道了分离和鉴定嗜热乳酸菌以及乳酸菌应用于木质纤维素生产高浓度 乳酸.当高温发酵生物脱毒处理的玉米秸秆生产乙醇时,发现有乳酸大量积累.从含乳 华东理工大学博士学位论文 第II 页 酸的乙醇发酵液中分离到一株嗜热产乳酸菌,鉴定并命名为乳酸片球菌 Pediococcus acidilactici DQ2,分离的微生物能够在高温(48 ℃)下同步糖化与发酵生物脱毒的玉米 秸秆迅速生产乳酸,乳酸浓度和得率分别到

75 g/L 和63%.高温、厌氧发酵、低营养需 求,木制纤维素依赖的特点,使P. acidilactici DQ2 为同步糖化转化纤维素原料生产乳酸 提供了良好的机遇,这一研究的创新点为首次分离到能够产乳酸的嗜热菌 Pediococcus acidilactici DQ2 并在高温下成功实现同步糖化与发酵木质纤维素原料生产乳酸. 本论文分别使用酵母 S. cerevisiae DQ1 和P. acidilactici DQ2, 高固含量下对稀酸预 处理的玉米秸秆进行同步糖化与发酵,分别获得

48 g/L 乙醇和

75 g/L 乳酸,这一结果 为木质纤维素高温加工提供了重要的技术保障, 在纤维素高温发酵领域具有重要的应用 价值. 关键字:玉米秸秆;

纤维乙醇;

纤维乳酸;

高温同步糖化与发酵;

纤维素酶活分析 Fermentation of Lignocellulose at High Temperature for Ethanol and Lactate Production Abstract One of the major technical barriers in the simultaneous saccharification and fermentation (SSF) of lignocellulose is the mismatch of the optimal temperature between the fermenting microorganims and the cellulolytic enzymes. In the present tudy, a smiplied method of cellulase activity determination based HPLC assay was proposed. And, effects of different fermentation parameters on the SSF of the dilute acid pretreated corn stover using Saccharomyces cerevisiae DQ1 at high solids loadings at elevated temperatures were detailed carried out. Futhermore, a lignocellulose-dependent themophilic lactate producing strain Pediococcus acidilactici DQ2 was discovered and employed in the SSF of corn stover for lactate production. High titre ethanol and lactate were successfully achieved by the SSF of lignocellulose at high temperatures. At the part one of the research work, a simplied cellulase assay method was presented based on HPLC assay. The method was according to the good linear relationships between logarithms of filter paper units measured by DNS method and sum concentrations of glucose and cellobiose measured by HPLC. Furthermore, the ratio of glucose to cellobiose could be obtained to characterize a cellulase for the capacity of enzymatic hydrolysis of cellulose into monomeric sugars. The innovative point of the method was the application of the specifically analytical tool HPLC for measuring the sugar concentrations which could give a meaningful index Cthe ratio of glucose to cellobiose.The performance of commercial cellulases had significant difference when enzymatic hydrolysis of the corn stover. The ratio of glucose to 华东理工大学博士学位论文 第III 页cellobiose in the hydrolysate could be increased with supplementation of cellobiase to the cellulase. At the part two of the research work was on the SSF of corn stover for ethanol production at elevated temperatures. The corn stover before use was pretreated with a method of dilute acid pretreatment and then washed with water once to reduce the inhibitors. The SSF experiments were conducted with the strain Saccharomyces cerevisiae DQ1 in a