外源添加亮氨酸提高乳酸乳球菌酸胁迫抗性

Exogenous Leucine Improved the Acid Tolerance of Lactococcus lactis Under Acid Stress

在乳酸乳球菌生长过程中外源添加浓度为10mmol/L的亮氨酸,可有效提高乳酸乳球菌在酸胁迫环境下的酸耐受性。在酸性环境中(pH5.0),添加亮氨酸的菌株的生物量为对照菌株的1.24倍;经过酸胁迫(pH4.0)5h后,添加亮氨酸菌株的存活率是对照菌株的28.5倍。进一步的研究表明,亮氨酸的添加可提高胞内NH4+浓度,有效的维持酸胁迫环境下胞内pH(pHin)的稳定,并有效维持乳酸脱氢酶(LDH)的活性,从而有效提高了乳酸乳球菌对酸胁迫的抵御能力。

The addition of leucine was proved to improve the tolerance of Lactococcus lactis NZ9000 to acid stress.When cultivated with leucine under acid stress（pH 5.0）,the biomass of L.lactis NZ9000（Leu^＋） increased 1.24 fold,compared to L.lactis NZ9000（Leu^-）（without leucine addition）.After challenged at pH 4.0 for 5h,the survival rate of L.lactis NZ9000（Leu^＋） increased 28.5 fold,compared to L.lactis NZ9000（Leu^-）.Further measurements indicated that the addition of leucine could improve the concentration of intracellular NH4^＋,help to maintain the intracellular pH（pHin） at a relatively high level and protect the activity of lactate dehydrogenase（LDH）.Therefore,the addition of leucine could enhance the acid tolerance of L.lactis.