Membrane damage and enzyme inactivation of Lactobacillus plantarum by high pressure CO2 treatment

Physiological changes of Lactobacillus plantarum (KFRI 815) by high pressure CO2 treatment were investigated to examine the relevance to microbial inactivation. Characteristic properties of the cells measured in this study included salt tolerance, release of UV-absorbing substances, Mg and K ions, proton permeability, glycolysis, H+-ATPase and constitutive enzymes, and dye uptake. The cells treated with high pressure CO2 of 7 MPa at 30 degrees C for 10 min showed the irreversible cellular membrane damages including loss of salt tolerance, leakage of UV-absorbing substances, release of intracellular ions, collapse of proton permeability and uptake of Phloxine B dye. L. plantarum cells after CO2 treatment also exhibited reduced glycolytic activity and inactivation of some constituent enzymes. However, H+-ATPase of the cell membrane maintained its initial specific activity of about 2.50 U/mg protein even though viability of the cells was reduced by several log cycles after high pressure CO2 treatment.