Influence of processing conditions on Bifidobacterium animalis subsp. lactis functionality with a special focus on acid tolerance and factors affecting it

Due to its technological feasibility, Bifidobacterium animalis subsp. lactis is the most widely used Bifidobacterium species in probiotic applications. Fermenter-scale growth of B. animalis subsp. lactis in GEM (a medium supporting well the growth of bifidobacteria) followed by freeze-drying produced preparations with good storage stability. However, a decrease in the acid tolerance of preparations was observed during the storage at elevated temperatures. Pepsin protected the cells during an exposure to low pH. Addition of pepstatin A (pepsin inhibitor) or N,N′-dicyclohexylcarbodiimide (DCCD; an inhibitor of proton translocating enzymes) decreased the protective ability at pH 2.0, while heat treatment did not have an influence on it. Measurement of membrane potential changes (DiBAC4(3)) showed that pepsin decreased hyperpolarization of the cells during an exposure to low pH suggesting that the protective ability is linked to the H+-ATPase activity of the cells. Our findings indicate a need for assessing parameters related to cell functionality in addition to culture-based stability of probiotic preparations.