一株低温纤维素降解菌的筛选与产酶条件优化

Screening of a low-temperature cellulose-degrading bacterium and optimization of cellulase production conditions

针对牛粪冬季堆肥存在启动慢、发酵周期长的问题,解决的有效办法是向堆体中添加低温纤维素降解菌剂,而目前可利用的低温纤维素降解微生物的种类较少。本研究在低温条件下从冻牛粪中分离得到1株低温高效纤维素降解菌,菌株命名为YSX-3,经鉴定为假单胞菌属(Pseudomonas)。为获得YSX-3菌株最佳的产酶条件,在单因素优化基础上以培养时间、培养温度、初始p H值和接种量为自变量,纤维素酶活性为响应变量,采用响应面分析法(RSM)分析响应变量与自变量之间的关系。结果表明:YSX-3菌株最佳产酶条件为接种量4%、培养温度9℃、培养时间71 h、初始pH值6.5,此培养条件下纤维素酶活为130.21 U·mL^(-1),与优化前相比提高了1.3倍。将优化后YSX-3菌株接种于牛粪堆体中,第5天进入高温期(>50℃),温度最高可达62.5℃,高温期持续时间为9 d;至堆肥结束时,堆体纤维素降解率达45.2%,而对照组堆体纤维素降解率仅为15.4%。

An effective solution to resolve the problems of slow start of cow manure composting and long fermentation cycle in winter is the addition of low-temperature cellulose-degrading microbe to the pile.However,few types of low-temperature cellulose-degrading microbe are available.In this study,one low-temperature and high-efficiency cellulose-degrading strain was isolated from frozen cow dung under low temperature conditions,which was named YSX-3.It was identified as Pseudomonas.In order to obtain its optimal enzyme production condition,on the basis of single factor optimization,incubation time,incubation temperature,initial pH value and inoculum amount are considered as independent variables,and cellulase activity as the response variable.Response surface analysis(RSM)was used to analyze the relationship between response variable and the independent variables.The results showed that the optimal enzyme production condition of YSX-3 strain was as follows:inoculating amount 4%,culture temperature 9℃,culture time 71 h and initial pH 6.5.Under this condition,the cellulase activity was 130.21 U·mL^(-1),which was 1.3 times higher than that before optimization.The optimized YSX-3 strain was inoculated into the manure pile.On the fifth day,the high-temperature period came(>50℃),the temperature reached up to 62.5℃,and the high temperature period lasted for nine days.At the end of composting,the degradation rate of cellulose reached 45.2%,while that in the control group was only 15.4%.