一株利用乳酸产丁酸梭菌BEY8的鉴定及其特性

Identification and Characterization of a Clostridium BEY8 Producing Butyrate from Lactate

摘要:

从窖泥中分离到一株能利用乳酸产丁酸的菌株BEY8，基于16S rRNA基因序列的系统发育分析显示， BEY8应为梭菌属，与酪丁酸梭菌模式株DSM 2637有99.8％的基因相似性. BEY8 菌体生长和代谢乳酸的最适pH为5.5-6.0，当pH过低（pH4.8）或过高（pH6.5）菌体均出现明显的生长和代谢延滞，但最终仍能完全将乳酸转化为丁酸；此外，当乳酸浓度达到156mM时，BEY8的生长及代谢同样出现延滞，且延滞时间随乳酸浓度的升高而延长，但最终都能完全将乳酸转化为丁酸，这些特性表明该菌有较强的环境适应能力及代谢稳定性. 在pH4.8时，外加乙酸可显著缩短BEY8的生长延滞期，并提高其对乳酸的代谢速率，但乙酸不能作为菌体的唯一能源生长，而只作为电子受体参与代谢乳酸产丁酸.

Abstract:

A lactate-utilizing bacteria BEY8 was isolated from the pit mud and produced butyrate with lactate. Based on phylogenetic analysis of 16S rRNA gene sequences, strain BEY8 should belong to the genus Clostridium. The most closely related type strain is Clostridium tyrobutyricum DSM 2637, with 99.8％gene similarity. The optimal values of pH for bacterial growth and lactate metabolism were found to be 5.5-6.0. The lag time of bacterial growth and lactate metabolism were observed at pH 4.8 and pH6.5, but finally lactate could be converting to butyrate as main metabolic product. In addition, when the concentration of lactate was more than 156 mM, the lag time of bacterial growth and lactate metabolism were also observed, and the arrearage time increase as increasing lactate concentration, but finally lactate could mainly be convert to butyrate as metabolic product. It was suggested that the isolate has a potential to adapt environment change, and these environmental factors do not affect the change of bacterial metabolic pathway. Furthermore, at pH4.8, the addition of acetate can significantly reduce the lag time of BEY8 growth and improve the metabolic rate of lactate. But acetate could not serve as the sole energy source for bacterial growth, and just as electron acceptor in metabolism of lactate and butyrate production.