高产纤维素酶产生菌的筛选、鉴定及发酵条件优化

Screening and identification of cellulase-producing strain andoptimization of the fermentation conditions

为充分利用废弃桑枝资源,更好运用纤维素酶到饲料添加剂中,本研究从桑园获取土壤为菌种来源,以羧甲基纤维素钠(CMC-Na)为唯一碳源获得一株高产纤维素酶菌株,经形态学和分子生物学鉴定为贝莱斯芽孢杆菌(Bacillus velezensis),命名为Bacillus velezensis XL3。对其发酵条件进行优化,在单因素试验基础上,采用Plackett-Burman设计筛选出具有显著影响菌株产酶的因素,并利用最陡爬坡试验确定响应面试验的适宜范围,设计三因素三水平的Box-Behnken试验。结果表明:影响菌株XL3发酵的显著因素分别是温度、pH和发酵时间,XL3产纤维素酶的最佳发酶条件为:温度34.73℃、pH 5.26、发酵时间6 d,经试验验证,菌株产酶酶活为(233.540±1.74)U/mL,是优化前的1.28倍。该研究为桑枝纤维素资源化利用奠定了理论基础。

To make full use of the resources of waste mulberry branches,which would better use of cellulase in feed additives,a cellulase-producing strain was obtained from the soil of mulberry field,with sodium carboxymethylcellulose(CMC-Na)as the only carbon source.According to its morphology and molecular biology,the strain was identified as Bacillus velezensis and named as Bacillus velezensis XL3.The medium composition and fermentation conditions for this strain to produce cellulase were optimized by the single factor experiment,the main factors which affected cellulase activity were evaluated by Placket-burman design,three significant factors were selected and the optimal area of the response surface methodology was determined by the steepest climbing experimental,the optimal fermentation conditions were obtained by using a three-factor and three-level Box-Behnken experiment.The results showed that temperature,pH and fermentation time were the significant factors for B.velezensis XL3 fermentation and the optimal fermentation conditions for the strain producing cellulase were:the fermentation temperature 34.73℃,initial pH 5.26 and fermentation time 6 days.Under this optimum condition,the cellulase activity reached(233.540±1.74)U/mL,which was about 1.28 times higher than that before optimization.The study provided a theoretical foundation for the utilization of mulberry branch cellulose.