随着纤维素酶需求量的增加，高效的纤维素分解菌以及纤维素酶的获取已经成为世界研究的热点，特别是在生物能源和生物有机肥领域。纤维素的分解主要由微生物分泌的纤维素酶来完成。纤维素酶是指能够水解纤维素及其衍生物的一系列酶的总称，主要包括内切葡聚糖酶、外切葡聚糖酶、β-葡萄糖苷酶，它们相互协同来完成纤维素分解。影响纤维素酶产生的因素不仅受到微生物种类的影响，同时也受到培养基组分，碳源，氮源，矿物质，温度和水分，特别是pH的影响。本文主要研究不同初始pH对哈茨木霉NJAU4742分解木质纤维素的影响，主要研究结果如下： 1.以水稻秸秆为唯一碳源，哈茨木霉NJAU4742能够在初始pH3.0-8.0的液体培养基中利用秸秆生长，并且能将初始pH 3.0，4.0，5.0，6.0和7.0的液体培养基平均增加一个pH单位，而初始pH为2.0，9.0和10.0的处理在整个培养期间pH保持稳定。哈茨木霉NJAU4742的固体发酵试验结果表明：哈茨木霉NJAU4742在pH6.0条件下生长最快，胞外蛋白浓度最高（36.3 mg?g-1），酶活力强（内切葡聚糖酶活：87.3 U?g-1，木聚糖酶活：244.4 U?g-1），水稻秸秆分解效果也是最佳的。当初始pH为3.0时，哈茨木霉NJAU4742可提高生长培养基的pH值，使得发酵基质达到其最适生长环境。在该初始pH条件下，菌株仍具有较高的胞外蛋白浓度（28.9 mg?g-1），酶活力（外切葡聚糖酶活：39.0 U?g-1，内切葡聚糖酶活：45.6 U?g-1），也能高效分解水稻秸秆。核磁共振（NMR）分析结果表明：固体机制中主要以alkyl-C，O-alkyl-C，aromatic C，carboxyl and carbonyl C等类型的碳存在，尤其以O-alkyl-C类型的碳居多，而O-alkyl-C类型的碳主要与碳水化合物相关，说明固体发酵过程中，碳水化合物的降解受pH影响较大。 2.根据以上的基础试验，通过SWATH分析技术分析菌株NJAU4742在不同的pH条件下分泌的纤维素酶的数量和丰度，深入地研究了哈茨木霉NJAU4742在不同pH条件下各种蛋白的表达差异,结果表明：SSF3.0与SSF6.0处理相比，蛋白表达量具显有显著差异的蛋白共有224个，而表达量显著上调蛋白有100个，表达量显著下调蛋白有124个。SSF9.0与SSF6.0处理相比，蛋白表达量有显著差异的一共有251个，其中表达量显著上调的有103个，表达量显著下调的有148个。通过将所鉴定的所有蛋白质分类发现，糖苷水解酶和蛋白酶蛋白质丰度在70%以上，在降解水稻秸秆中起重要作用。碳水化合物酶类分析结果表明：不同pH条件下，碳水化合物酶类分泌水平具有明显差异。在SSF6.0中，菌株NJAU4742分泌的纤维素酶和半纤维素酶最高，但在SSF3.0中哈茨木霉NJAU4742也能分泌较多的纤维素酶和半纤维素酶来实现水稻秸秆的高效分解。胞外蛋白丰度的分布分析表明：不同pH条件下木霉NJAU4742分泌的胞外蛋白酶种类无明显差异，但是为了满足水稻秸秆的快速分解并获取自身所需要的养分，各种蛋白分泌的比例存在显著的差异。

With the increasing demand of cellulase, acquisition of efficient cellulolytic microorganisms and cellulase are becoming more and more popular in the world, especially in biofuel and organic fertilizer field. The process of cellulose decomposition is mainly accomplished by cellulase secreted by microorganisms. Cellulase is a general term for a series of enzymes which can hydrolyze cellulose and its derivatives, mainly including endo-glucanase, exo-glucanase and β-glucosidase. Those cellulase usually work together to decompose cellulose. The secretion of cellulase is affected not only by the type of microorganisms, but also by the component of culture medium, such as carbon and nitrogen sources, minerals, temperature, water and pH values especially. The purpose of this study was to understand the effect of different pH values on the decomposition of lignocellulose by Trichoderma harzianum NJAU4742. Our conclusions are as follows. 1. Liquid-state fermentation was carried out with rice straw as the sole carbon resource. Trichoderma harzianum NJAU4742 could grow on straw in liquid medium with initial pH of 3.0-8.0, and could also increase the initial pH of 3.0, 4.0, 5.0, 6.0 and 7.0 by an average of one pH unit, while the treatments with initial pH of 2.0, 9.0 and 10.0 remained stable throughout the culture period.The results indicated that Trichoderma harzianum NJAU4742 grew fastest at pH value of 6.0. The concentration of extracelluar enzyme achieved the highest value (36.3 mg?g-1) in the treatment of 6.0, and the activity of enzymes were the strongest ( 87.3 U?g-1 for endoglucanase and 244.4 U?g-1 for xylanase), which also meant the best decomposition effect for rice straw. NJAU4742 could increase the pH value of the medium to its optimum growth environment with an initial pH of 3.0. Under this condition, the strain still keeps a high concentration of extracellular protein (28.9 mg?g-1) and enzyme activity ( 39.0 U?g-1 for exoglucanase and 45.6 U?g-1 endoglucanase), which meant that it could decompose rice straw efficiently. The analysis of NMR indicated that solid fermentation mainly consists of alkyl-C, O-alkyl-C, aromatic C, carboxyl and carbonyl C. Among them, O-alkyl-C took the greatest percent, which was related to the carbohydrates mainly. The results showed that the degradation of carbohydrates was greatly affected by pH during solid fermentation. 2. Based on the results above, the quantity and abundance of cellulase secreted by strain NJAU4742 under different pH conditions as well as the expression differences of various proteins were analyzed by SWATH, and the results are listed as follows. The proteomic analysis was compared between SSF3.0 and SSF6.0 treatment, and there were 224 proteins with significantly differential expression, among which 100 proteins were significantly up-regulated and 124 were significantly down-regulated in SSF3.0. The proteomic analysis result of SSF9.0 and SSF6.0 treatment was also compared, and there were 251 proteins with significant differential expression. Among them, 103 proteins were significantly up-regulated and 148 were significantly down-regulated in SSF3.0. The classification of all the identified proteins indicated that the abundance of glycoside hydrolase and protease was above 70%, and they might play a key role in the degradation of rice straw. The results of carbohydrate enzymes analysis showed that the secretion level of carbohydrate enzymes was significantly different under different pH conditions. In SSF 6.0 treatment, the cellulase and hemicellulase enzymes secreated by NJAU472 reached the highest level. However, in SSF3.0 treatment, NJAU4742 could also secret enough enzymes to decompose the rice straw efficiently. Distribution analysis of extracellular protein abundance showed that there was no significant difference in the types of extracellular proteases secreted by Trichoderma NJAU4742 under different pH conditions. However, in order to decompose rice straw and obtain necessary nutrients rapidly, there were significant differences in the proportion of protein secretion.