特异性木聚糖酶促进肉鸡小麦日粮肠道乳酸菌增殖机理

The production of corn can’t meet the needs in our country, and wheat is often used to replace corn in broiler production. However, wheat can’t be completely digested by broiler because of abundance of arabinoxylan, which cause broiler diarrhea and even death because of the microorganism disorder. Although xylanase is supplemented in wheat-diet of broiler, the effect is indistinctive owing to the branch structure of arabinoxylan. In our previous study, we found the specific xylanase composed of ferulic acid esterase, arabinofuranosidase, and xylanase, could improve the hydrolysis effect of arabinoxylan by twice, and proliferation of Lactobacillus by 2.7 times. However, the mechanism is not clear. This project aims to determine the best composition and suitable supplementation level of specific xylanase based on the quantity of dominant Lactobacillus, which is isolated and characterized from intestinal tract of broiler fed by different combination and level of xylanase with ferulic acid esterase and arabinofuranosidase. The composition and structure of the product from arabinoxylans hydrolyszate by specific xylanase in intestinal tract of broiler will be determined. The purified product will be used to culture the dominant Lactobacillus isolated from intestinal tract of broiler. Using the technology of transcriptional analysis and metabonomics, genes related to combine, transport, and metabolize selectivity by Lactobacillus with the purified product will be screened and analyzed. The molecular mechanism that specific xylanase improve the proliferation of Lactobacillus in the intestinal tract of broilers will be clarified. This project will supply a design solution of enzyme preparation to improve intestinal tract healthy for broiler production.

我国玉米产量不能满足产业需求，饲料中常用小麦替代玉米。但小麦富含阿拉伯木聚糖，黏性高，不能被肉鸡降解，造成肠道菌群紊乱，进而引起腹泻，甚至死亡。虽然添加木聚糖酶有所缓解，但其效果受到木聚糖支链结构的影响。我们前期发现由木聚糖酶与两种木聚糖支链酶组成的特异性木聚糖酶，提高木聚糖的水解率近1倍，水解产物提高乳酸菌增殖2.7倍，但其作用机理并不清楚。本项目通过研究不同木聚糖酶组合和添加量对小麦日粮肉鸡肠道阿拉伯木聚糖降解产物低聚寡糖的组成与结构，乳酸菌含量的影响，经过分离与鉴定，根据优势乳酸菌种类和功能确定特异性木聚糖酶的组成；体外通过用不同结构低聚寡糖培养乳酸菌，并基于转录组、代谢组技术，测定乳酸菌表面识别蛋白、转运蛋白、代谢酶、增殖等功能基因表达及代谢产物的差异，探明乳酸菌选择性利用低聚寡糖的“黑箱”，阐明特异性木聚糖酶促进肉鸡小麦日粮肠道乳酸菌增殖的分子机理，改善肉鸡小麦日粮肠道健康。

乳酸菌有利于畜禽肠道健康。小麦含有大量的抗营养因子——阿拉伯木聚糖，使用时没有被降解则有害于畜禽健康。将阿拉伯木聚糖（AX）降解成低聚木糖（XOS），形成益生元可以有效促进乳酸菌的增殖，促进肠道健康。首先，研究了由AX主链降解酶 （内切型木聚糖酶））和支链降解酶 （阿拉伯呋喃糖苷酶和阿魏酸酯酶）形成的特异型木聚糖酶体外酶解木聚糖的协同效应，结果比单独添加木聚糖酶提高水溶性木聚糖或不溶性木聚糖效果提高72%和36%，XOS的产量分别提高137.65%和94.66%。进一步通过肉鸡饲养试验证明，特异型木聚糖酶具有比木聚糖酶单独添加更好的改善肉鸡生产性能以及肠道乳酸菌的效果。为了阐明特异型木聚糖酶促进乳酸菌增殖的机理，从肉鸡盲肠中分离出一株能高效利用XOS的优势乳酸菌，通过16S rDNA技术和生化鉴定该细菌为乳酸片球菌，命名为BCC-1。de-novo 测序技术分析表明，BCC-1包含1条染色体和2个质粒，NCBI数据库收录号分别为 CP018763、CP018764和CP018765。采用转录组技术分析表明，该菌具有有机酸的转运、碳水化合物的代谢、磷酸烯醇式丙酮酸依赖的糖磷酸转移酶系统、糖基水解作用以及O-键连接的糖基水解作用。此外，通过体外增殖，培养形成Pediococcus acidilactic BCC-1产品，无论是单独添加还是与低聚木糖联合添加到肉鸡饲料中，均可进一步改善肉鸡生产性能效果，降低肉鸡空肠的食糜黏度，提高肉鸡盲肠食糜中丁酸的含量，改善肠道健康效果。16S rDNA测序结果表明，添加该乳酸菌具有提高肉鸡微生物多样性和厚壁菌门与拟杆菌门比值的作用。盲肠食糜代谢组分析结果表明，该乳酸菌可以提高肉鸡盲肠中肌醇和4-羟基苯丙酮酸，5-羟基吲哚-3乙酸和葡萄糖酸的含量。该结果为改善小麦日粮的利用，开发新型特异型木聚糖酶和新型益生菌产品提供了理论基础和实践指导。