产酸性木聚糖酶链霉菌的鉴定、酶学特性及发酵工艺研究

Research on identification,enzymatic characteristic and fermentation process of Streptomyces producing acid xylanase

木聚糖是谷物类饲料中的主要抗营养因子。为筛选高效降解半纤维素的菌株，提高粗饲料利用率，本试验采用水解圈法从土壤中筛选出1株产木聚糖酶的细菌，经鉴定为灰略红链霉菌，命名为Streptomyces griseorubens WL003。该菌所产木聚糖酶的最适酶促反应温度和pH分别为65℃、4．5，于30～55℃处理10min后，残余酶活不低于80％：于pH3．5～11．0处理1．5h，残余酶活仍保持在88％以上；Tween-80可提高木聚糖酶活力，而Cu^2＋．SDS及β-巯基乙醇则会较强地抑制酶活。该菌株以9％接种量接种至最适发酵培养基，碳源为10％麦秸，氮源为1．41％牛肉膏，0．1％吐温-80，初始pH为6．0，经32℃、180r／min下培养7d时，所产木聚糖酶活性最高，可达50．82u／InL，为优化前2．5倍。菌株WL003对麦秸的粗纤维降解效果最好，对苜蓿草粉的粗纤维降解效果最差。证明从土样分离到的酸性木聚糖酶菌株WL003，在降解饲料粗纤维方面具有较好的应用潜力。

The cereal diet enriches in xylan,which is an non-starch polysaccharides as anti-nutrients for animals.The aim of this research was to isolate hemicellulose-decomposing strains with high enzyme activity.A new xylanase producing strain was selected,which was identified as Streptomyces griseorubens,named Streptomyces griseorubens WL003.The xylanase produced by Streptomyces griseorubens WL003 showed optimal activity was at 65 ℃ and p H 4.5.The residual xylanase activity was over 80% after treatment at 30 ~ 55 ℃ for 10 min.The residual xylanase activity was over 88% after treatment at p H 3.5 ~ 11.0 for 1.5 h,which showed the xylanase had good p H stability.Tween-80 could promote the enzyme activity,while Cu2 +,SDS andβ-mercaptoethanol significantly inhibited the activity.The best liquid fermentation conditions for xylanase production showed as follow:fermentation time 7 d,inoculum dose 9%,initial p H 6.0,fermentation temperature 32 ℃,tween-80 0.1%,wheat straw 10%,nitrogen source 1.41%,shaking speed 180 r/min,the average activity of xylanase reached to 50.82 U/m L,and it was 2.5-fold of that before the optimization.The best effect of the crude fiber degradation was observed in wheat straw,however,the lowest effect of the degradation of crude fiber was found in alfalfa meal.Xylan-decomposing strain WL003 separated from soil sample could produce acid-stable xylanase and behave better development potential on crude fiber degradation.