秸秆纤维素降解真菌QSH3-3的筛选及其特性研究

为了获得高效降解秸秆纤维素的微生物菌株，采用滤纸降解法和刚果红染色法从含纤维素类物质的土壤中筛选到一株产纤维素酶菌株QSH3-3，通过形态观察和ITS序列分析，鉴定为草酸青霉Penicillium oxalicum QSH3-3。摇瓶产酶试验结果表明，该菌株的最佳产酶条件为:碳源为0.5%的碱处理过的玉米秸秆粉，氮源为0.2% 硫酸铵，起始pH为7，接种量为5%，产酶温度为30℃，培养时间为4 d。最佳产酶条件下，滤纸酶（FPase）、内切酶（CMCase）和木聚糖酶（Xylanase）分别为12 U、33 U、605 U（U为酶活性单位）；在15℃，其残余酶活力可达70%～80%；在pH 4～9 范围内，其残余酶活力可达70%以上。酶学稳定性研究表明，FPase、CMCase和Xylanase在pH 4～9范围残余酶活力达85%以上，具有较强的酸碱适应能力；FPase、CMCase和Xylanase在45℃以上酶活力迅速下降，耐热性较差。该菌株具有较高的木聚糖酶活力以及较强的低温、pH的耐受力，因而该菌株在田间温差大、土壤偏碱性等复杂条件下对秸秆纤维素类物质的降解具有较高的应用潜力。

Screening of a straw cellulose-degrading fungi QSH3-3 and study on its characteristics of cellulase production

In order to obtain the high effective straw cellulose-degrading microorganism,A cellulose-degrading fungi strain QSH3-3 was isolated from the rotten leaves and soil through methods of decolour congo red and decomposing filter paper,It was classified as Penicillium oxalicum QSH3-3 according to the analysis of its morphology and 18S rRNA gene sequences.The culture condition of cellulase production of stain QSH3-3 was studied under liquid fermentation condition.The results showed that the best carbon source was alkali-pretreated corn straw supply(5%),and the best nitrogen was(NH4)2SO4 supply(0.2%).The optimal conditions for cellulase production were as follows: the initial pH 6.5,the inoculation volume 5%,the cultivation temperature 30℃,the cultivation time 4 d.Under these optimum conditions,the activities of FPase,CMCase and xylanase were 12 U,30 U and 605 U(U indicated unit of enzyme activity),respectively.Their residual enzyme activities can up to 70% to 80% of the peak value at initial pH ranged from 4 to 9.Experimental results on the stability and properties of enzyme showed that FPase,CMCase and xylanase had high activity and stability from pH 4 to 9 with residual enzyme activities for over 85%.Activities of FPase,CMCase and xylanase were unstable when the temperature is above 45℃.These results indicated that strain QSH3-3 had developing potential to be used for the straw-returned-native-field.