Effect of pH on the growth of three lactic acid bacteria strains isolated from sour cream

Lactic acid bacteria (LAB) have an important role in the food industry because they are used in the production of fermented foods. To use these microorganisms in the food industry, it is necessary to obtain a high amount of biomass. One of the most important environmental factors in the growth of LAB is pH. Most of LAB species can tolerate a pH below 5.0, however, a suboptimal pH is expected to limit LAB growth. For this reason, the LAB strains Leuconostoc mesenteroides 67-1, Lactobacillus plantarum 60-1, and Streptococcus infantarius 46-3, isolated from sour cream, were grown in culture media under four different intial pH values to determine their optimal growth pH. Growth was assesed via colony-forming unit (CFU/ml) determination. We found that the growth of each LAB was affected by culture medium pH. We determined that the setpoints of pH for Leuconostoc mesenteroides 67-1, Streptococcus infantarius 46-3, and Lactobacillus plantarum 60-1 were of 4.5 (± 0.5), 5.5 (± 0.5), and 6.0 (± 0.5), respectively. We thus conclude that the growth of these LAB strains is pH-dependent (p < 0.05).