Maximum-biomass concentration prediction for Bifidobacteria in the pH-controlled fed-batch culture

Abstract

Our objective was to systematically study the relationship between maximum biomass concentration of different Bifidobacteria and total-acid anions accumulation, and develop a prediction equation for the maximum biomass concentration in the fed-batch culture at pH-controlled 7.0. The accumulation of acid anions and the consumption of nutrients of various strains were evaluated. In addition, minimum inhibitory concentrations (MICs) of acid anions on a range of strains were examined at pH 7.0. The inhibition of acid anions, which had the same MIC as sodium chloride, was due to the osmotic pressure under pH 7.0 conditions. Moreover, the concentration of total-acid anions completely inhibiting each strain in the fed-batch culture at pH-controlled 7.0 had no significant differences with the MIC of acid anions for the corresponding strains. The osmotic pressures under two conditions were not significantly different. Finally, the maximum biomass concentration of Bifidobacteria was found to be closely related to biomass yield per unit of acid anion produced (YX/P) and MIC (C) which were needed for the prediction, and different strains exhibited marked correlation (P < 0.01, R = 0.985). An equation for the prediction of the maximum biomass concentration was developed as follows: Xmax-X0 = (0.71 ± 0.03).YX/P.C.