PDF《木质纤维素来源发酵抑制物的生物降解以及光合发酵制氢 摘要》

华东理工大学硕士学位论文 第I页木质纤维素来源发酵抑制物的生物降解以及光合发酵制氢 摘要 木质纤维素在预处理过程产生的糠醛、羟甲基糠醛、乙酸、甲酸、乙酰丙酸等降解 产物对后续的酶水解和发酵过程产生了强烈的抑制.

这些抑制物的脱除即所谓的 脱毒 步骤是进行正常发酵的前提条件. 通过微生物降解的方法进行生物脱毒是最为有效的方 法之一.本文通过合成培养基初筛和预处理秸秆复筛,筛出三株能够降解预处理木质纤 维素中抑制物的真菌: Amorphotheca resinae ZN

1、 Penicillium polonicum ZN

2、 Penicillium turbatum ZN3,并用 16sDNA 的方法对菌种属性进行了初步鉴定.生长特性实验结果表 明,在抑制物浓度不高的条件下,A. resinae ZN1 能够在 pH 3-8,温度 20-32℃下正常生 长,并对氧需求不严格.该菌对各种抑制物单独存在时的最大降解浓度为乙酸 8g/l,甲酸9g/l,糠醛 4g/l,羟甲基糠醛 5g/l.对于典型稀酸预处理条件下处理的玉米秸秆,在30%固含量酶水解后的水解液主要成分为:葡萄糖 65g/l, 木糖 34g/l, 乙酸 9.0g/l, 甲酸 2.7g/l,糠醛和羟甲基糠醛 0.8g/l.酿酒酵母 Saccharomyces cerevisiae DQ1 在37℃下不 能在未经任何脱毒处理的水解液正常生长,而经过 A. resinae ZN1 脱毒

4 天后,S. cerevisiae DQ1 在同样条件下可以进行正常的同步糖化与发酵, 最终乙醇浓度可达 43g/l. 本论文的另一部分内容是利用木质纤维素来源发酵抑制物中的有机酸以及发酵过程产 生的有机酸进行光合发酵产氢.选用 Rhodobacter sphaeroides ZX-5 菌种,用于木质纤维 素油脂发酵后水解液的有机酸光合发酵制氢.实验结果表明,在30℃,4500lux 光照强 度下, R. sphaeroides ZX-5可将发酵废液中的有机酸和残糖完全降解, 氢气得率8ml H2/ml effluent.将有机酸利用起来光合发酵制氢,不仅可以解决生物燃料工业废水处理,而且 可生产洁净并具有经济性的氢能源. 关键词:木质纤维素;

预处理;

抑制物;

生物脱毒;

生物制氢 第II 页 华东理工大学硕士学位论文 Biodegradation of the lignocellulose derived inhibitor substrances in the pretreatment process and its photo-fermentation for hydrogen production Abstract The degradation products from lignocellulose pretreatment, such as furfural, 5-hydroxymethylfurfural (5-HMF), acetic acid, formic acid, levulinic acid etc. are the typical inhibitors for the cellulase enzymes and ethanol fermentation strains. Efficient degradation of these inhibitors ( biodetoxification ) is required for the following fermentation process. Biodegradation by microorganism is one of the most effective ways for inhibitors degradation. In this thesis, we isolated three fungi with the degradation capacity for the inhibitors by the two screening procedures in both the synthetic medium and on the pretreated corn stovers. The strains were identified as Amorphotheca resinae ZN1, Penicillium polonicum ZN2, and Penicillium turbatum ZN3 using the 16sDNA molecular identification method. A. resinae ZN1 grows well at the pH 3-8, 20-32℃, with or without oxygen when the inhibitors concentrations are not very high. The maximum concentrations degraded by the A. resinae ZN1 strain were acetic acid 8g/l;

formic acid 9g/l;

furfural 4g/l;

5-HMF 5g/l. The hydrolysate at 30% solid loading using the typical dilute acid pretreated corn stover contains glucose 65g/l, xylose 34g/l, acetic acid 9.0g/l, formic acid 2.7g/l, levulinic acid 3.2g/l, furfural and 5-HMF 0.8 g/l. The Saccharomyces cerevisiae DQ1 could not grow in this hydrolysate at