High Pressure Thermal Sterilization and ε-Polylysine Synergistically Inactivate Bacillus subtilis Spores by Damaging the Inner Membrane

This study was conducted to determine the sterilization effect of a combination of high pressure thermal sterilization (HPTS) and 6-polylysine (6-PL) on Bacillus subtilis spores. The spores were treated with HPTS (550 MPa at 25, 65, and 75 degrees C) and 6-PL at 0.1 and 0.3%. HPTS and 6-PL synergistically decreased the number of surviving spores and increased the release of the intracellular components in the spore suspension, with the maximal effects from treatment with 550 MPa at 75 degrees C plus 0.3% 6-PL. Maximum fluidity and permeability of the cell inner membrane were observed with 550 MPa at 75 degrees C plus 0.3% 6-PL. Changes in membrane lipids were detected from 3,000 to 2,800 cm(-1) by Fourier transform infrared spectroscopy. The results provide new insights into the mechanism by which HPTS and 6-PL synergistically sterilize B. subtilis spores. HIGHLIGHTS center dot HPTS plus 6-PL synergistically inactivated Bacillus subtilis spores. center dot HPTS plus 6-PL enhanced the fluidity and permeability of inner membrane. center dot Results provide insights into the sterilization mechanisms of this combination treatment.