外源添加亮氨酸提高乳酸乳球菌酸胁迫抗性

在乳酸乳球菌生长过程中外源添加浓度为10 mmol/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(pH 5.0) ,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(pH 4.0) 5 h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 5 h,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