【作者】 张鹏；

【导师】 叶勤； 鲍杰；

【作者基本信息】 华东理工大学 ， 生物化工， 2015， 硕士

【摘要】 乳酸片球菌Pediococcus acidilactici DQ2是一株从木质纤维素发酵体系中筛选获得的高抗逆野生乳酸菌。该菌株能够利用高固体含量的干法稀酸预处理的玉米秸秆,通过同步糖化与发酵生产高浓度的混合L-和D-乳酸。本文以热敏性自杀质粒pSET4E为工具质粒,通过同源重组方法敲除了P. acidilactici DQ2编码L-乳酸脱氢酶的基因ldh,获得了一株生产光学纯D-乳酸的工程菌株P. acidilactici ZP26。该菌株能够利用葡萄糖生产光学纯度达99.32%的D-乳酸。ldh基因的敲除不影响菌株的生长特性、乳酸得率和对抑制物的耐受性,而葡萄糖代谢速率和乳酸发酵速率降低。本文以干法稀酸预处理和生物脱毒后的玉米秸秆为原料,使用工程菌株P.acidilactici ZP26进行了25%(w/w)固体含量下的同步糖化与乳酸发酵。研究发现,抑制物降解和乳酸积累与生物脱毒时间密切相关,表明玉米秸秆原料中抑制物含量的减少是乳酸发酵性能提高的重要因素。P. acidilactici ZP26利用脱毒10天的玉米秸秆产生极高发酵指标的D-乳酸产品,D-乳酸终浓度、乳酸产率和乳酸得率分别是77.78 gL-1、1.02 g L-1h-1和66.06%。本工作对玉米秸秆生产光学纯D-乳酸具有重要意义。更多还原

【Abstract】 Pediococcus acidilactici DQ2, isolated from the lignocellulose fermentation system, is a wild lactic acid-producing strain with high resistance. Based on simultaneous saccharification and fermentation (SSF), P. acidilactici DQ2 could ferment the dry dilute acid pretreated corn stover and produce high titer D/L-lactic acid at high solids loading. A genetically modified strain, P. acidilactici ZP26 was constructed by the disruption of the gene Idh encoding L-lactate dehydrogenase in P. acidilactici DQ2 by homologous recombination method using the thermosensitive suicide plamid pSET4E. P. acidilactici ZP26 produced optically pure D-lactic acid and the optical purity reached 99.32%using glucose as feedstock. It showed that the disruption of Idh had no influence on the cell growth, lactic acid yield and the tolerance to different inhibitors generated from the pretreatment of lignocellulose, while the glucose consumption and lactic acid productivity decreased.The simultaneous saccharification and lactic acid fermentation by P. acidilactici ZP26 was carried out using the pretreated and detoxified com stover as feedstock at 25%(w/w) solids loading. The study showed that inhibitor degradation and lactic acid accumulation were closely related to the detoxification time. Therefore the decerase of inhibitors in com stover was the important factor which leaded to the promoted lactic acid fermentation. Optically pure D-lactic acid with extremely high fermentation parameters was produced by P. acidilactici ZP26 using the com stover which detoxified for 10 days. And the D-lactic acid titer, productivity and yield reached 77.78 g L-1,1.02 g L-1 h-1, and 66.06%.This works is much important for the production of optically pure D-lactic acid using com stover.更多还原