一株瘤胃源乳酸利用菌的分离鉴定及其体外代谢特性

Isolation and in vitro metabolic characterization of a lactate-utilizing bacterium from goat rumen

【目的】从饲喂高精料的本地山羊瘤胃内分离到一株利用乳酸并能产生大量丙酸的菌株L9,并进一步研究了该菌在调控瘤胃微生物发酵中的作用。【方法】采用厌氧培养技术,结合形态、生理生化特性和16S rRNA基因序列分析结果。【结果】该菌株被鉴定为反刍兽新月形单胞菌(Selenomonas ruminantium)。该菌株体外代谢特性研究表明,L9可利用乳酸作为唯一碳源,该菌在24 h内可对90 mmol/L的乳酸完全降解。体外摸拟瘤胃急性酸中毒的发酵试验结果表明,以淀粉为底物时,与对照组相比,添加菌株L9可显著降低瘤胃微生物体外培养体系中乳酸浓度,提高pH值,提高总挥发性脂肪酸和丙酸浓度,并显著降低乙酸与丙酸的浓度比(P<0.05)。【结论】结果显示,菌株L9是一株可代谢乳酸,促进丙酸生成,提高总挥发性脂肪酸浓度的有益瘤胃细菌。

[Objective] A lactate-utilizing, propionate-producing bacterium, strain L9, was isolated from rumen of goat fed with high concentrate by utilizing modified Hungate technique and anaerobic culture technique. The effect of the strain L9 culture on the rumen fermentation was further studied. [Methods] According to the characteristics of morphology, physiology, biochemistry tests and sequence comparison of 16S rRNA gene, strain L9 was identified as selenomonas ruminantium. The influence of strain L9 culture on in vitro rumen fermentation was studied using mixed rumen micro-organisms of goats as inoculums. [Results] The results of the metabolism experiment showed that it was capable of using lactate as the sole carbon source, and 90mmol/L lactate in LH medium could be completely utilized after 24h incubation. As compared with the control, strain L9 culture addition significantly increased the total volatile fatty acids （ TVFA）, the percentage of propionate and pH value, while reduced the ratio of acetate to propionate and lactate production （P〈0.05）. [Conclusion] The results suggested that strain L9 can reduce lactic acid production and enhance the TVFA and propionate production in in vitro fermentation, and thus could be beneficial for the fermentation of rumen microorganisms.