一株产纤维素酶菌株的分离、鉴定及产酶特性

【目的】筛选并鉴定一株产纤维素酶的菌株,初步探究该菌的产酶特性,为综合利用纤维素筛选菌源。【方法】在常温条件下,采用滤纸培养基对菌种富集,采用CMC-Na初筛纤维素降解菌,采用LB培养基分离纯化菌株,经形态学、生理生化特征试验、16S r RNA基因序列测定等分析筛选菌株的系统分类地位。单因素试验确定培养时间、培养温度、初始p H及Na Cl浓度对筛选菌株产酶活力的影响。【结果】从腐烂的玉米秸秆中分离出一株在常温下产纤维素酶细菌KZ-2,根据菌落形态特征、生理生化特征鉴定以及16S r RNA基因序列分析,初步鉴定KZ-2为肠杆菌(Enterobacter sp.),为潜在新种。产酶条件实验显示:该菌使用产酶发酵培养基120 h产酶量达到最大值,在25–35°C、初始p H 4.5–5.5、Na Cl浓度1.0%–2.0%范围内为最佳产酶条件,在最适条件下酶活可达80.93 U/m L。该菌株所产纤维素酶最适反应p H为7.0,最适反应温度为50°C。【结论】KZ-2是一株具有降解纤维素能力的细菌,在常温下即可分泌纤维素酶,并且该菌株为潜在新种,具有潜在的开发价值。

Isolation, identification and characterization of a cellulase-producing strain

Objective] To obtain microorganism strains for comprehensive utilization of cellulose, an ambient temperature cellulase-producing strain was isolated and identified. The optimal culture conditions for enzyme production were determined. Methods] Filter paper medium was used to enrich the microorganism cultures. CMC-Na medium was used to screen the cellulose-degrading strains initially under the condition of ambient temperature. A strain, KZ-2, was isolated and purified using LB medium, followed by identification utilizing morphological, physiological and biochemical properties, and 16S rRNA gene sequence profiles. Single factor test based on incubation time, culture temperate, initial pH and sodium chloride (NaCl) concentration was performed to optimize the conditions for cellulase production. Results] Strain KZ-2, capable of producing extracellular cellulase under ambient temperature, was isolated from decomposing maize straw. It was identified as a strain of Enterobacter sp. and potentially to be a novel species. The optimized enzyme production could be obtained when the strain was cultivated for 120 hours at 25-35 °C with initial pH 4.5-5.5, NaCl concentration of 1.0%-2.0%. The maximum cellulase activity of 80.93 U/mL was achieved under the optimal conditions. Initial enzymatic property analyses of the cellulase produced demonstrated that the enzyme was most active at pH 7.0 with a temperature of 50 °C. Conclusion] The cellulose-degrading strain KZ-2 is able to secrete cellulase under ambient temperature and is potentially a novel species. The strain is expected to be further studied and developed to explore its marketing values.