猪不同肠段微生物体外培养对蛋氨酸的代谢特性

Metabolic characteristics of methionine by in vitro fermentation with bacteria from different swine intestinal segment

摘要:

[目的]旨在通过微生物体外发酵技术，以回肠微生物为参照，研究猪盲肠及结肠微生物对在小肠微生物中代谢率较低的蛋氨酸的代谢特性。[方法]采集4头健康100 kg左右杜×长×大杂交猪的盲肠、结肠与回肠食糜作为接种物，分别接种于10 mmol/L蛋氨酸的培养基中，37℃体外培养24 h。分别设含蛋基酸溶液和含各肠段食糜接种物的空白对照组。[结果]（1）不同肠段微生物以蛋氨酸为底物体外发酵，盲肠组蛋氨酸消失率（21.9%）显著高于结肠组（16.7%）与回肠组（16.3%）（P<0.05）。盲肠组总SCFA量显著高于结肠与回肠组（P<0.05），伴随着pH值下降程度最高；盲肠组MCP产量也显著高于结肠与回肠组（P<0.05）；在产气量与NH₃-N浓度上，盲肠组与结肠组均显著低于回肠组（P<0.05）。（2）以蛋氨酸为底物体外发酵，门水平上，总菌、厚壁菌门含量在各肠段组间无显著差异（P>0.05），拟杆菌门含量在盲肠组最高；与不加蛋氨酸底物的对照组比较，三个肠段试验组总菌、厚壁菌门含量均显著高于对照组（P<0.05），而拟杆菌门含量在试验组与对照组间差异不显著（P>0.05）。属水平上，盲肠组和结肠组大肠杆菌属数量显著低于回肠组（P<0.05），而柔嫩梭菌属和梭菌XIV属数量在盲肠组和结肠组均高于回肠组；各肠段组间双歧杆菌数量无显著差异（P>0.05）。[结论]以蛋氨酸为底物，体外培养猪盲肠微生物对蛋氨酸代谢率高于回肠微生物，伴随着其他发酵参数的变化，并且发酵产生更多的菌体蛋白。相比于回肠微生物发酵，大肠微生物发酵后，柔嫩梭菌属和梭菌XIV属数量较高，而大肠杆菌属数量较低。

Abstract:

[Objective] This study aims to study metabolic characteristics of methionine by caecal and colonic bacteria compared with ileal bacteria from pigs using in vitro fermentation. [Methods] We took ileal, caecal and colonic chyme from four Duroc×Landrace×Yorkshire hybridization pigs as inoculum, and fermented in vitro separately. Control group 1 was without adding the chyme and Control group 2 was without adding methionine. [Results] Methionine disappeared 21.9% in the cecum group, significantly higher than that in the ileum group (16.3%) and colon group (16.7%) (P<0.05). The cecum group had the highest amount of short chain fatty acids (P<0.05), with the highest decrease of pH value. Moreover, the cecum group had the highest concentration of microbial crude protein, compared with the other two groups (P<0.05). Nevertheless, gas production and ammonia nitrogen (NH₃N) concentration in the ileum group were significantly higher than those in the cecum and colon group (P<0.05). At the phylum level, total bacteria and Firmicutes population were similar among all groups (P>0.05), and the counts of Bacteroidetes was highest in the cecum group. At the genus level, Escherichia coli counts in the cecum and colon group were significant lower than that in the ileum group (P<0.05), whereas the counts of Clostridium leptum and Clostridium cluster XIVa in the cecum and colon group were both higher than those in the ileum group. Bifidobacterium counts were similar among all groups (P>0.05). [Conclusion] In vitro fermentation using methionine as a substrate, the utilization rate of methionine by caecal bacteria is higher than that by ileal bacteria from pigs, accomplished with altering other fermentation parameters and producing microbial protein. Compared with in vitro fermentation of ileal bacteria, the counts of Clostridium leptum and Clostridium cluster XIVa are higher, whereas the Escherichia coli counts is lower after fermentation of the large intestinal bacteria.