88D-2 |
Characteristics of Leuconostoc isolates from Kimchi and their identification by ITS-PCR Ribotyping methodology |
S. S. YOON1, E. S. Jung1, W. S. Chin1, F. Breidt2, and H. P. Fleming2. (1) Biological Resources and Technology, Yonsei University, 234 Maeji-Ri, Heungup-Myon, Wonju-Shi, Kangwon-Do, 220-710, South Korea, (2) Food Science Research Unit, USDA-ARS-South Atlantic Area, North Carolina State Univ., 322 Schaub Hall, Box 7624, Raleigh, NC 27695-7624 Kimchi is a traditional, fermented Korean food that is prepared through a series of processes; specifically brining, fermentation, and blending of various spices and other ingredients. Despite intensive previous studies, the microbial diversity is largely unknown in Kimchi. It is generally believed that the fermentation is initiated by various microorganisms originally present in the raw materials, but in fact the fermentation is gradually dominated by lactic acid bacteria(LAB). Among these bacteria, Leuconostoc mesenteroides is the predominant species in the early fermentation stages followed by homofermenters such as L. plantarum. Leuconostocs are heterofermentative and not able to grow at 45C or in the presence of 8% NaCl, even with an optimum growth temperature of 20 to 30C. The objective of this study is to confirm the dominant Leuconostoc species during the fermentation under different temperatures (4, 10 and 20C). Baechu(Chinese cabbage)-Kimchi was prepared by mixing typical ingredients as described in the standard procedure. Based on the colony morphology and vancomycin-resistance(30 ug/ml), a total of 127 isolates were tentatively recovered as presumptive Leuconostoc species. To examine their biochemical characteristics, an API 50 CHL kit was used to identify twenty strains out of total 127 primary isolates from the Kimchi samples owing to their frequent recovery on the Leuconostoc selective medium. Eleven strains were in agreement with the typical Leuconostoc database. For physiological aspects, however, most of the presumptive Leuconostoc isolates were grown in the modified MRS-broth containing 10% cabbage juice at 4C and 30C, but four and seventeen strains failed to grow at 37 and 45C, respectively. Interestingly, all of the test strains grew in the presence of 50% bile juice or artificial gastric juice of pH 3.0 and some strains were able to grow under a 9% NaCl condition. Also, seventeen strains can survive 500 ug/ml vancomycin in the modified MRS broth (pH 6.8). The ribosomal intergenic transcribed spacers (ITS) between the conserved 16S rDNA and the 23S rDNA genes vary in length and sequence among different species or even subspecies. In this study, the data obtained by ITS-PCR ribotyping showed that three strains didn't coincide with Leuconostoc type strains at all, strongly suggesting that these strains are new species or subspecies in the Leuconostoc genus.
Session 88D, Food Microbiology: General
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