西藏地区牦牛瘤胃中兼性厌氧纤维素降解菌的分离鉴定

本研究旨在从西藏地区牦牛瘤胃中分离出具有分解纤维素能力的兼性厌氧菌,为青贮饲料微生物添加剂的研制提供支持。试验采集了西藏那曲地区成年牦牛的新鲜瘤胃液,经刚果红染色初筛,滤纸降解复筛,获得分解纤维素能力强的菌株,对菌株生长速率及酶活力进行测定,经形态学、生理生化特性和16S rRNA序列分析对菌株进行鉴定,并分析了菌株对水稻秸秆的降解效果。试验分离出一株兼性厌氧纤维素降解菌,属于肠球菌属,即粪肠球菌(Enterococcus faecalis) JF85。菌株JF85在15~55 ℃,pH 3.0~7.0及3.0%和6.5% NaCl培养基中生长良好。接种JF85,36 h后可获得最大内切葡聚糖酶活力(0.41 U/mL)和滤纸酶活力(0.13 U/mL)。在模拟发酵试验中,接种菌株JF85,14 d后水稻秸秆干物质、纤维素和半纤维素含量与对照组相比显著降低(P<0.05);在发酵第7天,JF85处理组显示最高的可溶性碳水化合物含量,整个发酵过程中木质素含量变化不显著(P>0.05)。菌株JF85具有分解纤维素、耐酸、耐盐特性,在青贮饲料生产中具有较好的应用前景。

Isolation and identification of facultatively anaerobic cellulolytic bacterium in the rumen of Tibetan yaks (Bos grunniens)

This study aimed to isolate and identify facultatively anaerobic cellulolytic bacterium in the rumen of yaks and to provide a basis for studying new types of silage additives.Fresh ruminal fluid was collected from Tibetan yaks and highly cellulolytic facultatively anaerobic bacteria were screened out by using Congo red staining and liquid secondary screening culture media.Cellulolytic bacteria strains were identified based on their morphological,physiological and biochemical characteristics,as well as by 16S rRNA analysis.Time course profile of growth and enzyme production by strain JF85 was obtained.The degradation efficiency of rice straw was examined by evaluating cellulose,hemicellulose and lignin contents under a range of condition.Strain JF85 was identified as Enterococcusfaecalis.This strain grew well across a wide range of conditions:temperatures of 15-55 ℃,pH levels of 3.0-7.0 and NaCl levels of 3.0％ and 6.5％.It exhibited the maximal endoglucanase activity (0.41 U/mL) and filter paper activity (0.13 U/mL) after 36 hours of incubation.In simulated fermentation,compared to the control,adding the JF85 strain significantly decreased the dry matter,cellulose and hemicellulose contents of rice straw after 14 days of inoculation (P＜0.05).JF85-treated rice straw showed its highest water soluble carbohydrate content after 7 days of inoculation.However,there were no significant differences in lignin contents among all treatments.Applications of the JF85 strain,with its highly cellulolytic abilities and tolerance of acid and salt,have the potential to significantly improve the production of silage.