秸秆纤维素降解细菌的筛选及产酶条件优化

摘要

Bacteria,which could effectively degrade the cellulose,was isolated and screened from the rotting straw soil.The classification of this bacteria and its optimal enzyme production conditions were determined.The sodium carboxymethyl cellulose hydrolysis circle method,filter paper disintegration,enzyme activity determination method were used to screen bacteria strains.The effects of straw length,incubation time,nitrogen sources,nitrogen dosage and pH value on enzyme production were inverstigated in straw enzyme production medium.Two strong degradation ability strains were isolated,which were named XY2 and XY6 respectively.Through the 16 S rRNA sequence analysis,strain XY2 belongs to the Burkholderia mimosarum; strain XY6 belongs to the Enterobacter.The optimal enzyme production conditions for strain XY2 is 30 ℃,pH 6.0,4 cm straw segment as the carbon source,0.5％ ammonium sulfate as the nitrogen source; for strain XY6,the optimal enzyme production conditions is 30 ℃,pH 6.0 for rice straw or 8.0 for wheat straw,4 cm straw segment as the carbon source.And 5‰ sodium nitrate for rice straw or ammonium sulfate as the nitrogen source for wheat straw.The enzyme activities changed a little in a week.%从富含腐烂秸秆的土壤中分离、筛选出降解纤维素较为有效的细菌,鉴定其类别,并对其产酶条件进行优化研究.利用羧甲基纤维素钠水解圈法、滤纸崩解法、酶活测定法筛选菌株,并对秸秆液体产酶培养基中不同秸秆长度、培养时间、氮源、氮源投加量和培养基初始pH对酶活性的影响进行了研究.结果筛选出秸秆纤维素降解能力较强的两株菌株XY2和XY6.经鉴定XY2属于伯克霍尔德菌属(Burkholderia mimosarum),XY6属于肠杆菌属(Enterobacter).菌株XY2的最优产酶条件为:温度30℃,培养基初始pH为6.0,碳源为4 cm长度的水稻秸秆或小麦秸秆,氮源为0.5％硫酸铵；菌株XY6的最优产酶条件为:温度30℃,4 cm长度秸秆段为碳源,而在以水稻秸秆为惟一碳源时,最适氮源为0.5％的硫酸铵、培养基初始pH为6.0,以小麦秸秆为惟一碳源时最适氮源为0.5％的硝酸钠、培养基初始pH为8.0,氮源为5‰硝酸钠或硫酸铵,且在一周之内酶活性变化较小.