Effects of exposure to combined acid-cold stress and repair processing on the heat tolerance of Lactobacillus paracasei LP4

Abstract

To enhance the heat tolerance of lactobacillus in the process of industrial application, the effects of combined acid-cold stress and bacterial repair processes were investigated in Lactobacillus paracasei LP4. The results showed that compared with the control group without stress (10.36% ± 1.75%), the survival rate of the strain after heat treatment was significantly increased after treatment with combined acid-cold stress at pH 3.5 and 20 °C for 1.5 h followed by repair at 35 °C for 15 min (50.68% ± 1.95%, p < 0.05). Analysis of the underlying mechanism showed that compared with single stress, the combined acid-cold stress promoted biofilm synthesis, thus establishing a protective layer surrounding the cell and reducing heat damage to the cell membrane. It was also found to induce the synthesis of peptidoglycans and surface proteins to reduce cell wall damage and improve survival under high temperatures. Additionally, repair processes after combined acid-cold stress were found to reduce DNA damage caused by acid stress, further enhancing heat tolerance. These findings suggest means of improving the heat tolerance and commercial application of lactobacillus through the use of combined acid-cold stress and repair processes.