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Culture supernatant produced by Lactobacillus kefiri from kefir inhibits the growth of Cronobacter sakazakii

Published online by Cambridge University Press:  22 February 2018

Dong-Hyeon Kim
Affiliation:
Center for One Health, College of Veterinary Medicine, Konkuk University, Seoul, 05029, South Korea
Dana Jeong
Affiliation:
Center for One Health, College of Veterinary Medicine, Konkuk University, Seoul, 05029, South Korea
Kwang-Young Song
Affiliation:
Center for One Health, College of Veterinary Medicine, Konkuk University, Seoul, 05029, South Korea
Il-Byeong Kang
Affiliation:
Center for One Health, College of Veterinary Medicine, Konkuk University, Seoul, 05029, South Korea
Hyunsook Kim
Affiliation:
Department of Food & Nutrition, College of Human Ecology, Hanyang University, Seoul 04763, South Korea
Kun-Ho Seo*
Affiliation:
Center for One Health, College of Veterinary Medicine, Konkuk University, Seoul, 05029, South Korea
*
*For correspondence; e-mail: bracstu3@konkuk.ac.kr

Abstract

Cronobacter sakazakii is a life-threatening foodborne pathogen found in powdered infant formula and dairy products. Kefir is a dairy probiotic product and its antimicrobial activity against C. sakazakii was reported in our previous study. To identify key microorganisms that mediate growth suppression, we tested the antimicrobial activity of culture supernatants derived from lactic acid bacteria found in kefir. Lactobacillus kefiri DH5, L. kefiranofaciens DH101, and B ifidobacterium longum 720 (a commercial probiotic strain that served as a positive control) all significantly inhibited the growth of C. sakazakii ATCC 29544, delaying the initiation of exponential growth from 3 to 9 h in the nutrient broth. Among them, L. kefiri DH5 exerted the strongest antimicrobial effects against C. sakazakii, showing bactericidal effect at the addition of 300 µl of supernatant in 1 ml of nutrient broth. Interestingly, the supernatant of L. kefiri DH5 has higher pH and lower titrable acidity than that of L. kefiranofaciens DH101, suggesting metabolites produced by heterofermentation of L. kefiri acted more effectively to antagonise the growth of C. sakazakii. In addition, the supernatant of L. kefiri DH5 induced the leakage of cytoplasmic materials including nucleic acid and proteins, suggesting L. kefiri DH5 disrupted the cellular membrane integrity of C. sakazakii. Considering that pH neutralisation reduced the L. kefiri-dependent growth suppression, it is inferred that this activity is mainly due to organic acids produced during the fermentation process.

Information

Type
Research Article
Copyright
Copyright © Hannah Dairy Research Foundation 2018 

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