猪小肠微生物对不同蛋白源的体外发酵特性比较

【目的】采用体外发酵技术比较小肠微生物对不同蛋白源的发酵规律。【方法】以成年猪的十二指肠、空肠和回肠内容物为接种物,以豆粕、菜粕或鱼粉水解物上清液为氮源底物,于发酵的0、4、8、12 h分别测定发酵液p H、微生物蛋白、氨氮和挥发性脂肪酸含量,同时提取细菌DNA并进行定量分析。【结果】添加含氮底物的空肠组和回肠组氨氮浓度和菌体蛋白浓度均相对增加,尤其是酶解菜粕组菌体蛋白合成量较高;十二指肠组菌体蛋白浓度以及氨氮含量不断减少。各发酵组乳酸和挥发酸快速积累,4–8 h积累量最大;8 h后空肠组和回肠组乳酸和挥发酸含量相对稳定,而十二指肠组后期丙酸含量增加约2 mmol/L,并伴随着乳酸含量的相对减少。同时,各组中总细菌、拟杆菌门、厚壁菌门和乳酸杆菌数量相对增加,且略高于无氮组,但不同蛋白源组间无显著差异。【结论】在体外培养条件下,空肠和回肠微生物具有相似的发酵规律,均能快速利用培养液中的含氮物质合成菌体蛋白;十二指肠微生物具有较强的产挥发酸能力,能够转化乳酸并大量产生丁酸和丙酸,这有利于宿主营养功能和肠道健康。

Effect of different nitrogen source on porcine small intestinal fermentation in vitro

Objective] We studied the effect of different nitrogen source on bacteria from porcine small intestine.Methods] Digesta samples from different segments of the small intestine were inoculated into media containing enzyme-treated protein (soybean meal, rapeseed meal or fish meal) and incubated for 12 h.Results] After incubation of jejunal and ileal microbes, the contents of ammonia and microbial crude protein increased in groups with nitrogen resources, especially the groups with rapeseed meal which had the highest increment of microbial crude protein. However, concentrations of microbial crude protein and ammonia decreased in duodenal groups. Besides, concentrations of volatile fatty acid and lactate increased in all groups, and acetate concentrations were more than 50% of the total volatile fatty acid concentration. The contents of propionate and butyrate increased in duodenal groups, whereas the contents of lactate decreased during the last four hours. However, propionate and butyrate were not changed in jejunal and ileal groups. The copy numbers of total bacteria, Firmicutes, Bacteroides and Lactobacillus increased during the experiment, but it was not significantly different between groups with different enzyme-treated protein.Conclusion] Protein after digestion would be utilized by jejunal and ileal microbes, which mostly used to produce microbial crude protein. Duodenal microbes would utilize lactate and produce propionate and butyrate.