Dynamic self-recovery of injured Escherichia coli O157:H7 induced by high pressure processing

Abstract This study was aimed to investigate the dynamic recovery process of high pressure processing (HPP)-injured Escherichia coli O157:H7. E. coli O157:H7 was treated with 100–500 MPa for 5 min, and the pressure with highest injury rate was selected to determine the optimal temperature and duration for repairing HPP-injured cells in PBS. The morphological and physiological changes during the repair process under the above optimal conditions were further investigated. The results showed a stronger inhibition effect with increased pressure, while the lethal effect was not consistent with the injury, since the highest injury rate was observed at 400 MPa for 5 min. Next, HPP-treated cells (400 MPa, 5 min) were repaired in PBS at different temperatures (20, 25, 30, 37 °C) for 108 h, and the optimal recovery condition of the injured cells was found to be 25 °C for 24 h. During the repair process, SEM and TEM morphology, leakage of ions, activities of Na + K + -ATPase and Ca 2+ Mg 2+ -ATPase, and the membrane fatty acid composition of HPP-treated cells gradually return to normal levels found in non-HPP cells, which confirmed the dynamic recovery process of HPP-injured E. coli O157:H7, as well as that HPP-injured E. coli O157:H7 could be repaired under appropriate conditions.