大熊猫肠道纤维素分解菌的分离鉴定及产酶性质

【目的】从健康大熊猫新鲜粪便中分离具有纤维素酶活性的菌株,并对其进行菌种鉴定及产酶性质研究。【方法】利用羧甲基纤维素钠培养基分离纯化具有较高纤维素酶活性的菌株,根据形态学特征、生理生化特性以及16S rDNA分析对其进行分类鉴定,研究影响该菌株纤维素酶的产酶条件,以及对不同纤维素底物的降解情况。【结果】分离得到一株纤维素酶产生菌株P2,该菌株为好氧的革兰氏阳性细菌,生长温度范围20-50℃(最适温度37℃),pH范围6.0-9.0(最适pH7.0),NaCl浓度范围0%-15%(最适2%NaCl),培养24h达到产酶高峰。16S rDNA基因序列分析显示,菌株P2与解淀粉芽胞杆菌(Bacillusamyloliquefaciens)NBRC15535相似性为99.66%。该菌株对四种纤维素底物(滤纸、脱脂棉、秸秆、竹纤维)均有不同程度的降解,内切葡聚糖酶、外切葡聚糖酶、β-葡萄糖苷酶和总酶活具有不同的酶活变化。【结论】本研究首次从大熊猫粪便中分离出了好氧纤维素分解菌,并鉴定为解淀粉芽胞杆菌,对上述四种纤维结构均有一定的破坏和分解作用,为进一步研究大熊猫竹纤维消化机制提供了菌源。

Isolation, identification and cellulase production of a cellulolytic bacterium from intestines of giant panda

Objective] To isolate and identify the cellulose-producing bacterium from fresh feces of healthy giant pandas,and characterize its cellulase production.Methods] A strain with high activity of cellulase was isolated and purified by carboxymethyl cellulose-Na(CMC-Na) medium.The morphological,physiological and biochemical characteristics and 16S rDNA gene were analyzed to identify the taxonomic position of the strain.Meanwhile,its cellulase producing conditions and degradation of several cellulose substrates were studied.Results]A cellulose-producing strain P2 was obtained.Strain P2 is a gram-positive and aerobic bacterium.Its growth temperature ranges from 20 to 50℃(optimum at 37℃) and pH 6.0 to 9.0(optimum at 7.0),and NaCl concentration at 0%-15%(optimum at 2.0%).It took 24 h to reach the peak of cellulase production.Phylogenetic analysis based on 16S rDNA sequence showed that strain P2 is most closely related to the Bacillus amyloliquefaciens NBRC15535 with the similarity of 99.66%.Strain P2 posses different abilities to degrade four different cellulose substrates including filter paper,absorbent cotton,straw,and bamboo fiber.During the degradation,it shows different enzymatic activity curves with endoglucanases,exoglucanases,β-glucosidases and cellulase.Conclusion] An aerobic cellulolytic bacterium was isolated from feces of giant pandas for the first time,and was identified as Bacillus amyloliquefaciens.Due to its ability to degrade the cellulose materials with different structures,strain P2 could be used in the further study on the digestion mechanism of bamboo of giant panda.