白蚁栖息环境中蜡状芽孢杆菌的分离及其纤维素酶活性分析

【目的】了解白蚁栖息环境中有无降解纤维素的微生物。【方法】以羧甲基纤维素钠为唯一碳源,利用刚果红染色,根据透明圈大小进行筛选。通过显微形态、革兰氏染色及16S rRNA基因序列分析对菌株进行鉴定。DNS法测定菌株产纤维素酶与生长周期的关系,并进一步分析纤维素酶性质。【结果】从台湾乳白蚁(Coptotermes formosanus Shiraki)栖息环境中筛选到一株具有较高纤维素酶活性,革兰氏阳性菌株TT15,16S rDNA序列分析鉴定为蜡状芽孢杆菌(Bacillus cereus Gd2T)。菌株培养前12 h没有纤维素酶活性,随着培养时间的增加,纤维素酶活性逐渐增大;当生长达到稳定期(48 h),酶活性达到最大并保持稳定。菌株TT15纤维素酶活性的最适pH和最适反应温度分别为5.0和50°C。【结论】从白蚁栖息环境中分离到一株具有较高纤维素酶活的蜡状芽孢杆菌TT15,可作为产细菌纤维素酶的优良菌株。

Isolation and characterization of a Bacillus cereus strain with cellulose-degradation activity from a termite-inhabiting soil

Objective] The study aims to determine whether the termite-inhabiting soil harbors cellulose-degradation bacteria. Methods] Using a selective medium supplemented with sodium carboxymethyl cellulose (CMC-Na) as the sole carbon source and the Congo red activity staining method, we have isolated a cellulose-degradation strain. Microscope morphology, Gram-staining, and 16S rRNA gene sequencing analyses were utilized to characterize the isolated strain. Enzyme activity and properties were assayed by the DNS method. Results] A Gram-positive strain (named as TT15) with high cellulase activity was obtained from a Coptotermes formosanus-inhabiting soil. Based on the 16S rDNA analysis, TT15 was identified to be a strain of Bacillus cereus Gd2T. The cellulase activity was not detected in the first 12 h of continuous culture, but afterwards, the enzyme activity was detected and increased with culture time. The activity reached the maximum level at the early stationary phase of growth (48 h) and remained stable later on. The optimum pH and temperature were 5.0 and 50 °C, respectively. Conclusion] We have isolated a B. cereus Gd2T strain TT15 with high cellulase activity from a C. formosanus-inhabiting soil. The strain might be used for biomass conversion biotechnology.