一株产木聚糖酶菌株的筛选及发酵产酶条件优化

摘要

以木聚糖为唯一碳源,从含有大量腐烂枯枝树叶土壤中筛选到一株高产木聚糖酶菌株,经形态学分析和分子学鉴定,确定其为链霉属(Streptomyces).通过单因素实验考察了碳源、氮源、初始pH值、发酵温度和发酵时间对酶活的影响;在单因素实验的基础上,利用Design-Expert软件对碳源、氮源和发酵时间进行响应面分析.单因素实验确定适宜发酵产酶条件为:复合碳源为玉米芯粉+蔗糖(1∶2)、氮源为硝酸铵、初始pH值4.0、发酵时间2.5d、发酵温度30℃,此时,所产木聚糖酶酶活为511 U· mL-1;响应面分析确定最优发酵产酶条件为:复合碳源(玉米芯粉:蔗糖=1∶2)添加量4.09％、氮源硝酸铵添加量1.16％、初始pH值4.0、发酵时间3.14d、发酵温度30℃,此时,所产木聚糖酶酶活达到641 U·mL-1,较单因素实验提高了25.44％.%Using xylan as a sole carbon source,we screened a high xylanase-producing strain from soil which contained a lot of rotten dead branch leaves.The strain belongs to Streptomyces by morphological analysis and molecular biology identification.We investigated the effects of carbon source,nitrogen source,initial pH value,fermentation temperature,and fermentation time on enzyme activity by single-factor experiment.On the basis of single-factor experiment,we carried out the response surface analysis of carbon source,nitrogen source,and fermentation time by Design-Expert software.The single-factor experiment showed that the enzyme activity of xylanase was 511 U · mL-1 when the appropriate fermentation conditions were as follows:composite carbon source was corncob powder and sucrose(1 ∶ 2),nitrogen source was ammonium nitrate,initial pH value was 4.0,fermentation time was 2.5 d,and fermentation temperature was 30 ℃.The response surface analysis showed that the enzyme activity of xylanase reached 641 U · mL 1 which increased by 25.44％ over that of single-factor experiment when the optimal fermentation conditions were as follows:the addition of composite carbon source(corncob powder ∶ sucrose=1 ∶ 2) was 4.09％,the addition of nitrogen source ammonium nitrate was 1.16％,initial pH value was 4.0,fermentation time was 3.14 d,and fermentation temperature was 30 ℃.