Effects of the repair treatment on improving the heat resistance of Lactiplantibacillus plantarum LIP-1

To improve the heat resistance of lactobacilli during spray-drying, we first investigated the effect of heat shock and repair treatment on the heat resistance of Lactiplantibacillus plantarum LIP-1, and the specific cell repair mechanism. Compared with control group, the reduction of the strain after the heat treatment (75 °C for 40 s) decreased from 1.05 to 0.36 log CFU/mL (initial cell counts 9.30 log CFU/mL) by heat shock (44 °C for 10 min). The residuals of the strain after heat-treated increased by 0.90 log CFU/mL by heat shock firstly, and then the repair treatment (30 °C for 10 min). During recovery period, the relative content of unsaturated long-chain fatty acids (C18:1n9 & C18:2n6) induced by heat shock proteins increased by 7.0%, and the amount of DnaK protein anchored on the cell membrane increased by 0.17 pg/mL. Cell membrane damage caused by heat shock was reduced and strain heat resistance was improved. Our research found that the repair treatment after heat shock reduced cell membrane damage caused by heat shock, which is a very promising technology for improving the heat resistance of L. plantarum LIP-1. This technology is also expected to be widely used in the preparation of LAB powders by spray-drying technology.