• Journal of the Korean Dietetic Association
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• v.24 no.4
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• pp.330-343
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• 2018

Recently, there has been a growing demand for natural preservatives because of increased consumer interest in health. In this study, we produced Lactobacillus rhamnosus cell-free supernatant (LCFS) and evaluated and compared its antimicrobial activity with existing natural preservatives against pathogenic microorganisms and in chicken breast meat contaminated with Escherichia coli and Staphylococcus aureus. Lactobacillus rhamnosus cell-free supernatant possessed 30 units of lysozyme activity and contained 18,835 mg/L of lactic acid, 2,051 mg/L of citric acid and 5,060 mg/L of acetic acid. Additionally, LCFS inhibited the growth of fourteen pathogenic bacteria, S. aureus, Bacillus cereus, Listeria monocytogenes, Vibrio parahaemolyticus, Listeria innocua, S. epidermidis, L. ivanovii, E. coli, Pseudomonas aeruginosa, Shigella sonnei, Shi. flexneri, Proteus vulgaris, Pseudomonas fluorescens, and Klebsiella pneumoniae. The antibacterial activity of LCFS was stronger than that of egg white lysozyme (EWL), Durafresh (DF) and grapefruit seed extract (GSE). Additionally, LCFS maintained its antimicrobial activity after heat treatment at $50^{\circ}C{\sim}95^{\circ}C$ and at pH values of 3~9. Moreover, LCFS inhibited the growth of E. coli and S. aureus in chicken breast meat. In conclusion, it is expected that LCFS, which contains both lysozyme and three organic acids, will be useful as a good natural preservative in the food industry.

• Food Science and Biotechnology
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• v.18 no.3
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• pp.761-765
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• 2009

The effects of probiotic bacteria on the functional properties of squid by-products were investigated during fermentation. Bifidobacterium longum, Lactobacillus acidophilus, Lactobacillus brevis, Lactobacillus casei, Lactobacillus paracasei, Lactobacillus rhamnosus, and Pediococcus acidilactici were used to ferment the squid by-products for 96 hr at $37^{\circ}C$. The numbers of all probiotics increased to $10^7-10^8$ CFU/g after 96 hr fermentation. No substantial pH changes were observed. L. rhamnosus and P. acidilactici showed the highest 2,2-diphenyl-1-picrylhydrazyl (DPPH) scavenging activities. Interleukin-6 (IL-6) and tumor necrosis $factor-{\alpha}$ ($TNF-{\alpha}$) secreted from B cells increased after adding the extracts of probiotic-fermented squid by-products. The human NK cells were grown well in the B cell-growing broth cultured with the extracts of squid by-products fermented by L. rhamnosus and P. acidilactici. Trimethylamine (TMA) and dimethylamine (DMA) contents were significantly decreased after probiotic-fermentation. Therefore, L. rhamnosus GG and P. acidilactici can be used for the fermentation of squid by-products and their use would provide benefits in functional food products.

• Journal of Microbiology
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• v.45 no.6
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• pp.515-520
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• 2007

Vaginal lactic acid-producing bacteria of 80 pre-menopausal women were studied by isolation on Blood and DeMan-Rogosa-Sharpe agar, PCR with group-specific primers for Lactobacillus-denaturing gradient gel electrophoresis (DGGE), and PCR with specific primers for V3 region in 16S rRNA-temporal temperature gel electrophoresis (TTGE). Conventional isolation method on media detected only one lactobacillus (Lactobacillus brevis) while TTGE detected only Lactobacillus sp. DGGE detected seven Lactobacillus species; L. coleohominis, L. crispatus, L. iners, L. reuteri, L. rhamnosus, L. vaginalis, and Leuconostoc lactis. L. acidophilus and L. gasseri, which are prevalent in Western women, were not detected in Korean women. Furthermore, L. rhamnosus, Leuc. lactis, L. coleohominis, and Weissella cibaria, which were not previously reported in the vaginal microbiota of Korean women, were detected. The five most prevalent LABs in vaginal microbiota in Korean women were L. iners, Enterococcus faecalis, L. crispatus, Leuc. lactis, and W. cibaria.

• 축산식품과학과 산업
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• v.9 no.1
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• pp.70-77
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• 2020

• Journal of Animal Science and Technology
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• v.48 no.6
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• pp.907-920
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• 2006

This study was conducted to investigate the inhibitory activity of Lactobacillus spp., Bacillus ssp., and calf fecal isolates against pathogenic Salmonella typhimurium, E. coli, Listeria monocytogenes, and Staphylococcus aureus. Among thirteen strains of Lactobacillus ssp. tested, Lactobacillus helveticus CU631 showed the highest inhibition against three pathogens, whereas Bacillus spp. showed a weak inhibitory activity. Four calf fecal isolates were identified as Lactobacillus pentosus CU13, CU05, Pediococcus pentosaceus CUR02, and Lactobacillus lactis ssp. lactis CUM14. The whole cell and cell wall components of L. rhamnosus CU02 and L. pentosus CU13 were active in the inhibition of L. monocytogenes. The medium components and levels, which affect on the inhibitory activity, were revealed as Tween 80 1.0%, peptone 3.0%, yeast extract 3.0%, glucose 3.0%, beef extract 3.0%, and NaCl 1.0～3.0%, respectively. Inhibitory activity of the supernatant culture medium was not affected by catalase and proteinase K treatment but affected by heat treatment at 80℃ and netralization, which implies that the inhibitory activity is due to the production of organic acids during the growth. L. pentosus CU13 and L. rhamnosus CU02 exhibited broad inhibition spectrum against 16 out of 21 strains including some pathogens. Oral administration of L. rhamnosus CU02 to the mice infected with E. coli O157:H7 was proven to be effective to recover their body weight during the experimental period.

• Animal Bioscience
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• v.34 no.9
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• pp.1525-1531
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• 2021

Objective: The objective of this study was to evaluate the antimicrobial effects of fermented Maillard reaction products made by milk proteins (FMRPs) on Clostridium perfringens (C. perfringens), and to elucidate antimicrobial modes of FMRPs on the bacteria, using physiological and morphological analyses. Methods: Antimicrobial effects of FMRPs (whey protein plus galactose fermented by Lactobacillus rhamnosus [L. rhamnosus] 4B15 [Gal-4B15] or Lactobacillus gasseri 4M13 [Gal-4M13], and whey protein plus glucose fermented by L. rhamnosus 4B15 [Glc-4B15] or L. gasseri 4M13 [Glc-4M13]) on C. perfringens were tested by examining growth responses of the pathogen. Iron chelation activity analysis, propidium iodide uptake assay, and morphological analysis with field emission scanning electron microscope (FE-SEM) were conducted to elucidate the modes of antimicrobial activities of FMRPs. Results: When C. perfringens were exposed to the FMRPs, C. perfringens cell counts were decreased (p<0.05) by the all tested FMRPs; iron chelation activities by FMRPs, except for Glc-4M13. Propidium iodide uptake assay indicate that bacterial cellular damage increased in all FMRPs-treated C. perfringens, and it was observed by FE-SEM. Conclusion: These results indicate that the FMRPs can destroy C. perfringens by iron chelation and cell membrane damage. Thus, it could be used in dairy products, and controlling intestinal C. perfringens.

• Food Science and Biotechnology
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• v.17 no.3
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• pp.587-593
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• 2008

Microbial exopolysaccharide (EPS) is a biothickener that can be added to a wide variety of food products, where it serves as a viscosifying, stabilizing, emulsifying, and gelling agent. The objective of this study was to investigate the optimum conditions of pH, incubation temperature, and whey protein concentration (WPC) for EPS production by Lactobacillus rhamnosus ATCC 9595. We found that maximal EPS production was achieved at a pH of 5.5 and temperature of $37^{\circ}C$. At the same fermentation conditions, EPS production was affected by the addition of L. rhamnosus GG (a weak-EPS producer). After growth for 24 hr, total EPS production was $583{\pm}15.4mg/L$ in the single culture system, and $865{\pm}22.6\;mg/L$ in the co-culture system with L. rhamnosus GG. Based on the presence of WPC, EPS production dramatically increased from $583{\pm}15.4$ (under no WPC supplementation) to $1,011{\pm}14.7\;mg/L$ (under supplementation with 1.0% WPC). These results suggest that WPC supplementation and the co-culture systems coupled with small portions of weak-EPS producing strain can play an important role in the enhancement of EPS production.

• Preventive Nutrition and Food Science
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• v.9 no.1
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• pp.7-13
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• 2004

Lactic acid fermentation of prickly pear extract (PPE) was performed by Lactobacillus rhamnosus LS, Lactobacillus bulgaricus, and Lactobacillus brevis. The PPE was pasteurized to eliminate indigenous microorganisms as well as to dissolve the partially insoluble pulp. The PPE fermented without yeast extract by L. rhamnosus LS exhibited 0.57％ acidity and 3.5${\times}$10$^{8}$ CFU/mL bacteria count. With the addition of 0.2% edible yeast extract the PPE fermented by L. rhamnosus LS exhibited 1.15％ acidity,2.7${\times}$10$^{9}$ CFU/mL bacteria count and 95.0% retention of red color. When 5％ fructose syrup was added, the PPE fermented by L. rhamnosus LS had 1.09% acidity, 6.5${\times}$10$^{8}$ CFU/mL, and 97.7% retention of red color. With 1∼3% (w/v) concentrations of starter, the PPE fermented by L. bulgaricus and L. brevis showed 0.97% and 0.65% acidities, respectively. The viable cell counts from L. rhamnosus LS fermentation were higher compared with those of other LAB. During cold storage at 4$^{\circ}C$, the viable cell count was well maintained for 3 weeks, but then rapidly decreased. The red pigment was highly stable during cold storage for 4 weeks. The pasteurized PPE fortified with 5% fructose syrup, 0.2% yeast extract, and 0.05% CaCO$_3$ was successfully fermented by inoculating with 3% LAB and incubating at 3$0^{\circ}C$ for 2 days. Both viable cell counts and the red color of the fermented PPE were well maintained during cold storage for 3 weeks.

• Journal of Microbiology
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• v.44 no.4
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• pp.439-446
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• 2006

In this study, the growth kinetics of Lactobacillus rhamnosus and lactic acid production in continuous culture were assessed at a range of dilution rates $(0.05 h^{-1}\;to\;0.40h^{-1})$ using a 2L stirred tank fermenter with a working volume of 600ml. Unstructured models, predicated on the Monod and Luedeking-Piret equations, were employed to simulate the growth of the bacterium, glucose consumption, and lactic acid production at different dilution rates in continuous cultures. The maximum specific growth rate of L. rhamnosus, ${\mu}_{max}$, was estimated at $0.40h^{-1}$I, and the Monod cell growth saturation constant, Ks, at approximately 0.25g/L. Maximum cell viability $(1.3{\times}10^{10}CFU/ml)$ was achieved in the dilution rate range of $D=0.28h^{-1}\;to\;0.35h^{-1}$. Both maximum viable cell yield and productivity were achieved at $D=0.35h^{-1}$. The continuous cultivation of L. rhamnosus at $D=0.35h^{-1}$ resulted in substantial improvements in cell productivity, of 267% (viable cell count) that achieved via batch cultivation.

• Applied Biological Chemistry
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• v.42 no.2
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• pp.83-90
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• 1999

Four strains of lactic acid bacteria which had cholesterol lowering activities were selected from foreign fermented milk. The strains were identified as Lactobacillus(L.) rhamnosus 2084, L. casei 0781, Lactococcus (Lacto.) lactis spp. 204, and Enterococcus(E.) faecium 402. We observed that the L. rhamnosus 2084 was the most tolerant against pH 1.5, L. casei 0781 against pH 2.0, but not significantly different in the tolerance against pH 3.0. The L. rhamnosus 2084 was the most tolerant against bile acid and prominent in the degree of lowering cholesterol level. All four strains were used as starters in producing yogurt, and then investigated physico-chemical characteristics, such as pH, titratable acidity, and viable cell counts of yogurt base. L. casei 0781, L. rhamnosus 2084, Lacto. lactis 204, and E. faecium 402 were incubated for 6 hours at $40^{\circ}C$, 4 hours at $40^{\circ}C$, 6 hours at $37^{\circ}C$, and 12 hours at $37^{\circ}C$ and $40^{\circ}C$, respectively, for the optimum conditions of fermented milk.