Response to Low pH Impacts the Fatty Acid Composition and the Thiol Content of Bifidobacterium

Abstract

Inducing at sublethal pHs can strengthen the survival rate of Bifidobacterium at the lethal pH. In this study, we determined the optimal inducing condition of Bifidobacterium and analyzed the effect of a low pH environment on fatty acid (FA) composition and thiol content in Bifidobacterium. The result indicates that inducing at pH 4.5 significantly improved the survival rate of Bifidobacterium at pH 3,5 and 3.0. After being induced at pH 4.5, the percentage of C18:1 increased significantly, while the percentage of C16:0 decreased significantly. The results suggest inducing treatment strengthened the membrane fluidity of Bifidobacterium. After being stressed at the lethal pH, the percentage of saturated FA increased significantly in both the control and induced cells, while the percentage of unsaturated FA decreased significantly. The results suggested that, to survive at the lethal pH, the cells strengthened the membrane rigidity and weakened the membrane fluidity to block the entrance of H+ by changing the FA composition in Bifidobacterium. In addition, after being stressed, the thiol content of the control cells was significantly lower than that of the induced cells. This study provided the first data proof that showed FA and thiol participated in response to low pH in Bifidobacterium.