• Journal of Dairy Science and Biotechnology
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• v.41 no.3
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• pp.138-148
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• 2023

In this study, Lactococcus lactis subsp. hordniae JNU533 (JNU533) was isolated from Swiss-type cheese, and the bacteriocin produced by this strain was characterized. The spot-on-lawn assay was used to determine the antimicrobial spectrum and characteristics of the JNU533-derived bacteriocin. Results confirmed that the JNU533-derived bacteriocin inhibited the growth of lactic acid bacteria. The size of the bacteriocin was approximately 4.9 kDa, and it was heat- and pH-stable under various temperature and pH conditions. Furthermore, the possibility of using JNU533 as a starter culture in the manufacturing of fermented dairy products was assessed. A single colony of JNU533 was inoculated into 10% skim milk containing 0.5% glucose to investigate its characteristics in milk culture. The decrease in the pH was similar to that elicited by Lactobacillus delbrueckii subsp. bulgaricus. Furthermore, the results confirmed that JNU533 inhibited the growth of various bacteria and could be used as a milk fermentation starter. This study highlights the characteristics of the bacteriocin produced by JNU533 and the growth features of this strain in a skim milk medium.

• Microbiology and Biotechnology Letters
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• v.52 no.1
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• pp.1-14
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• 2024

This study focused on isolating and identifying strains from the gut of Epinephelus akaara cultivated in aquaculture facilities on Jeju Island. The aim was to evaluate the potential of utilizing these strains as probiotics for industrial applications. A total of 129 strains were isolated from the gut of E. akaara and screened based on their ability to create a clear zone of 10 mm or more in a preliminary antimicrobial activity test. Twelve strains were selected for further analysis, including bile resistance, acid tolerance at different pH levels, antioxidant activity, antibiotic susceptibility, and biochemical characteristics using the API kit. Through these characteristic experiments, eight strains (G1, G3, G15, G21, B1, B2, B3, B5) were identified as having potential as probiotics. Among these, the B group strains (B1, B2, B3, B5) exhibited significantly higher activity compared to the G group strains (G1, G3, G15, G21). Based on the phylogenetic analysis of the 16S rRNA gene sequences of the selected microorganisms, the strains were named as follows: B1 strain as Lactobacillus paracasei B1, B2 strain as Lactococcus lactis B2, B3 strain as Lactobacillus plantarum B3, B5 strain as Lactococcus lactis subsp. hordniae B5, G1 strain as Bacillus licheniformis G1, G3 strain as Bacillus velezensis G3, G15 strain as Brevibacterium frigoritolerans G15, and G21 strain as Bacillus pumilus G21.

• Korean Journal of Microbiology
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• v.51 no.3
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• pp.209-220
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• 2015

In this study, gut bacterial communities in xylophagous insects were analyzed using the pyrosequencing of 16S rRNA genes for their potential biotechnological applications in lignocelluloses degradation. The result showed that operational taxonomic units (OTUs), species richness and diversity index were higher in the hindgut than in the midgut of all insect samples analyzed. The dominant phyla or classes were Firmicutes (54.0%), Bacteroidetes (14.5%), ${\gamma}-Proteobacteria$ (12.3%) in all xylophagous insects except for Rhinotermitidae. The principal coordinates analysis (PCoA) showed that the bacterial community structure mostly clustered according to phylogeny of hosts rather than their habitats. In our study, the two carboxymethyl cellulose (CMC)-degrading isolates which showed the highest enzyme activity were most closely related to Bacillus toyonensis $BCT-7112^T$ and Lactococcus lactis subsp. hordniae $NCDO\;2181^T$, respectively. Cellulolytic enzyme activity analysis showed that ${\beta}-1,4-glucosidase$, ${\beta}-1,4-endoglucanase$ and ${\beta}-1,4-xylanase$ were higher in the hindgut of Cerambycidae. The results demonstrate that xylophagous insect guts harbor diverse gut bacteria, including valuable cellulolytic bacteria, which could be used for various biotechnological applications.