Effects of fermentation conditions (salt concentration, temperature, and pH) on Lactobacillus strains for induction of interleukin-12 in the exposed murine splenocytes

The present work aimed to assess the stresses of temperature, salt concentration, and pH on <i>Lactobacillus gasseri</i> 54C, <i>Lactiplantibacillus plantarum</i> ATCC 14917, and 11SH in fermented culture medium and their effects on interleukin-12 (IL-12) induction in murine splenocytes. First, the strains were fermented under different microbial stress conditions at salt concentrations (2, 4, and 6 % w/v), temperatures (30 and 42 °C), and pH levels (4, 5, and 6), as well as their combined conditions. Then, they were heat-killed, lyophilized, and exposed to murine splenocytes. The IL-12 induction was measured using the immunoassay method. It was indicated that the induction of IL-12 depended on the culture conditions, as it was increased by the fermentation strains under microbial stresses with the higher temperature (42 °C), lower salt concentration (%2), and lower pH level (4). It seems that the bacterial cells' integrity is essential to stimulate the induction of IL-12.