一株高活性纤维素降解细菌的筛选鉴定及酶学特性

Isolation and Enzymatic Characteristics of a Cellulose-decomposing Bacteria Strain with High Cellulase Activity

利用小麦／玉米秸秆还田土壤样品，通过富集培养和刚果红平板染色法筛选分离出纤维素降解细菌XWS-12；对分离的菌株进行16SrRNA基因序列系统发育分析，初步鉴定为伯克氏菌属（Burkholderia），定名为Burkholderia sp．XWS-12。以玉米秸秆和麸皮为碳源，研究了氮源、发酵时间、初始发酵温度、培养基初始pH等条件对该伯克氏菌产纤维素酶的影响。结果显示，该菌株产纤维素酶最适氮源为硝酸钠，培养时间为60h，培养温度为37℃，培养基初始pH为4，该菌株的CMC酶活力最高，可达25U／ml。其粗酶液的最适反应温度为50℃，最适反应pH为5，在pH4～8的范围内酶活力较稳定。粗酶液的热稳定较差，当温度超过50℃时，该酶活力显著下降；当温度为50℃时，保温1h，该酶活力损失53％。

A highly active cellulose-decomposing strain XWS-12 was isolated from the soil of wheat and maize straw returning by enrichment culture and Congo red staining test. The isolated strain was identified by phylogenetic relationships based on 16S rRNA gene sequences, and this strain was preliminarily identified as Burkholderia sp. XWS-12. Using corn straw and bran as carbon source, the cellulase producing conditions of the bacterium were analyzed by single factor experiments, including nitrogen source, incubating time, initial temperature, initial pH et al. The results showed that the optimal cellulase producing conditions of Burkholderia sp. XWS-12 were as follows： the best nitrogen source was NaN03, incubating time was 60 h, initial temperature was 37℃and initial pH of culture medium was 4, under which the activities of the CMCase activity reached 25 U/m!. The optimal reaction temperature of the crude enzyme solution was 50℃, the optimum reaction pH value 5. In the range of pH 4-8, the enzyme activity was more stable. In different temperature conditions, the results of the enzyme activity change showed that when the temperature was more than 50℃, the enzyme activity decreased significantly. Under the temperature of 50℃ for 1 h, the loss of enzyme activity was above 53%.