Cross protection of lactic acid bacteria during environmental stresses: Stress responses and underlying mechanisms

Lactic acid bacteria (LAB) encounter various environmental stresses (acidic, thermal, osmotic, oxidative, ethanolic and others) during food fermentation and production. Cross protection is a phenomenon commonly existed in LAB which confers LAB higher tolerance to a harsh condition through preadaptation at mild stresses. Therefore, it is necessary to summarize the researches finished in the past years. In this review, we provide a comprehensive review of the stress responses and protective mechanisms of LAB during cross protection, and particularly focus on the physiological characters (accumulation of intracellular amino acids, maintenance the homeostasis of intracellular pH, and engineering cell membrane functionality) and multi-omics analysis (genes/ proteins involved in membrane transport, energy metabolism, amino acid metabolism, stress response chaperones and cell wall/membrane biosynthesis). In addition, based on the mechanisms of cross protection, strategies to improve the robustness of LAB under various stresses were also discussed.