저온성 김치 유산균 Leuconostoc gelidum 균주의 특성 규명

Abstract

In this study, 7 kimchi samples fermented at low temperature were collected from 7 different regions in Korea. Storage temperature, aging period, chemical properties of the collected samples were investigated. Microbial profiles of the samples were analyzed using polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE). Psychrotrophic lactic acid bacteria (LAB) were isolated from the samples using 25℃ incubation temperature. A total of 8 LAB were isolated, and then they were identified by determination of 16S rRNA gene sequences, biochemical properties, growth with 6.5% NaCl, growth with heme and plasmid profiles of the isolates. As a result, 2 LAB were identified as Leu. gelidum subsp. aenigmaticum and 6 LAB were Leu. gelidum subsp. gasicomitatum. The effects of different temperature (-2~37℃), initial pH (pH 4.0~pH 9.0) and initial NaCl concentration (1~9%) on the LAB growth were investigated. They can grow at 5℃ but not at 37℃, maximum cell growth can be obtained at 25℃ and pH 8.0. In safety test, the isolates did not present harmful characteristics such as hemolysis, undesirable enzyme activities, antibiotic resistance and biogenic amine production. The isolates were investigated for their suitability for technological processes (pH, temperature and NaCl treatment). In pH and temperature tolerance, all 8 strains were stable at pH 8.0, -2~10℃ for 72 h. And in salt tolerance test, Leu. gelidum subsp. aenigmaticum were stable at 3~5% (w/v) NaCl and Leu. gelidum subsp. gasicomitatum were stable at 7~9% (w/v) NaCl. The isolated strains showed exopolysaccharide (EPS) producing ability at 5% sucrose plate. The result of this study showed that the isolated psychrotrophic LAB can be used as a functional starter culture for food fermentation at low temperature.