LAUSR

BACKGROUND During high-cell-density culture of Lactobacillus fermentum, the optimal pH is often maintained by adding NaOH. During cultivation at controlled pH, L. fermentum experiences osmotic stress due to the continuous accumulation of sodium lactate as a neutralizer product, affecting its survival in subsequent processing. The purpose of this study was to evaluate the nutrient consumption patterns of L. fermentum ATCC 14931 under sodium lactate stress and to screen nutrients that help it resist osmotic stress. RESULTS The consumption and consumption rates of amino acids, purines, pyrimidines, vitamins, and metal ions were analyzed in chemically defined media containing 0.13, 0.31, or 0.62 mM sodium lactate. The highest consumption rates were found for arginine, guanine, folic acid, and Mn2+ , and the most consumed nutrients were glutamate + glutamine, guanine, ascorbic acid, and Na+ . Arginine 2.58 mM, guanine 0.23 mM, and Mn2+ 0.25 mM were added to the medium at sodium lactate concentrations of 0.13 and 0.62 mM, and arginine 2.58 mM, guanine 0.26 mM, and Mn2+ 0.25 mM at a sodium lactate concentration of 0.31 mM. The viable cell counts of L. fermentum ATCC 14931 were approximately 1.02-fold (P < 0.05) of the counts observed in control medium at all three concentrations of sodium lactate. CONCLUSION The present results suggest that certain nutrients accelerate the growth of L. fermentum under sodium lactate stress and enhance its resistance to this adverse condition. This article is protected by copyright. All rights reserved.