双峰驼源纤维素降解菌的筛选及其对酒糟的降解效果

骆驼作为荒漠、半荒漠地区的主要畜种，经过长期的自然选择，具有独特的生理功能，但目前对双峰驼源肠道中的纤维素降解菌研究较少。为了探究双峰驼粪便中具有纤维素降解能力的细菌，采用羧甲基纤维素钠（CMC-Na）平板法进行初筛，然后对其进行分离、纯化，并利用DNS法检测纤维素酶活力，根据透明圈的大小及纤维素酶活力，筛选出具有较强纤维素降解能力的菌株。结合形态学观察、生理生化特性及16S rRNA测序分析对筛选得到的菌株进行鉴定。对菌株接种量、初始pH、培养温度和发酵时间条件进行单因素优化，并在单因素的基础上进一步采用响应面优化。将优化后的菌液接种于酒糟中，探究第7、14和21 d菌液对酒糟的降解效果。结果表明，筛选得到的菌株YT5-1-1具有较强的纤维素降解能力，经鉴定YT5-1-1为香坊肠杆菌（Enterobacter xiangfangensis）。YT5-1-1的最适产酶条件为：接种量2.6%，初始pH 4.5，培养温度30 ℃，发酵时间43 h，预测CMCase活力最大为1.819 IU·mL^-1。菌株 YT5-1-1对酒糟发酵过程中的pH变化基本无影响，能维持更高的干物质含量，会显著降低酒糟中的中性洗涤纤维含量和酸性洗涤纤维含量；发酵结束时，试验组的半纤维素降解率和纤维素降解率较空白组分别提高了4.18%和3.46%。

Screening of Cellulose-degrading Bacteria from Bactrian Camel and Their Degradation Effect on Distillers Grains

As the main animal species in desert and semi-desert areas, camels have unique physiological functions after long-term natural selection. However, there were few studies on bactrian camel intestinal cellulose-degrading bacteria. In order to explore the bacteria with cellulose degradation ability in Bactrian camel feces, CMC-Na plate method was used for primary screening, then they were separated and purified, and the cellulase activity was detected by DNS method. According to the size of transparent ring and cellulase activity, the strain with strong cellulose degradation ability was screened out. The screened strains were identified by morphological observation, physiological and biochemical characteristics and 16S rRNA sequencing analysis. The conditions of inoculum amount, initial pH, culture temperature and fermentation time were optimized by single factor, and response surface optimization was further adopted on the basis of single factor. The optimized bacteria solution was inoculated into distillers grains, and the degradation effect of bacteria solution on distillers grains on the 7, 14 and 21 d were studied. The results showed that the screened strain YT5-1-1 had strong cellulose degradation ability, and it was identified as Enterobacter xiangfangensis. The optimum enzyme production conditions of YT5-1-1 were as follows: inoculum amount 2.6%, initial pH 4.5, culture temperature 30 ℃, fermentation time 43 h, and the maximum predicted activity of CMCase was 1.819 IU·mL^-1. Strain YT5-1-1 had no effect on pH change during distillers grains fermentation, and could maintain higher dry matter content, which would significantly reduce neutral detergent fiber content and acid detergent fiber content in distillers grains. At the end of fermentation, the degradation rates of hemicellulose and degradation of cellulose values for the YT5-1-1 group were 4.18% and 3.46% higher than those of the blank group, respectively.