The Acid-resistant Characteristic of Organic Acid Tolerance Mutant of Leuconostoc paramesenteroides

To investigate the acid tolerance characteristics of the acid-resistant mutant, Leuconostoc paramesenteroides P-200, as a kimchi starter, this study examine proton permeability, ATPase activity, glycolysis activity, release, and membrane fatty acid composition, and compared the data to that of its wild-type, L. paramesenteroides LP-W. In the proton permeability experiment, the LP-W and P-200 strains' average maximum half-time values for pH equilibration through the cell membrane were approximately 5.7 and 9.3 min in 150mM KCl solution, and 4.2 and 8.3 min in 3% NaCl solution, respectively. Their values and pH levels for maximal specific ATPase activity showed that P-200 had greater activity than LPW. And the results of pH-dependent glycolysis activity showed that P-200 had greater activity than LP-W. Furthermore, after 2 hr at pH 4.0, LP-W and P-200 had percent magnesium release values of approximately 12% and 34%, respectively. A comparison of their membrane fatty acid compositions indicated that C18 and cyclo-C19 were the major different fatty acids between the two strains, and their contents of C18 and cyclo-C19 were 2.5% and not detected, respectively, in LP-W, and 6.4% and 11.4%, respectively, in P-200. These results indicate that the P-200 strain has significantly improved acid tolerance as compared to its wild type, LP-W.