• Journal of Ginseng Research
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• v.42 no.4
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• pp.412-418
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• 2018

Background: Ginsenoside Rg3(S) and compound K (C-K) are pharmacologically active components of ginseng that promote human health and improve quality of life. The aim of this study was to produce Rg3(S) and C-K from ginseng extract using recombinant Lactococcus lactis. Methods: L. lactis subsp. cremoris NZ9000 (L. lactis NZ9000), which harbors ${\beta}$-glucosidase genes (BglPm and BglBX10) from Paenibacillus mucilaginosus and Flavobacterium johnsoniae, respectively, was reacted with ginseng extract (protopanaxadiol-type ginsenoside mixture). Results: Crude enzyme activity of BglBX10 values comprised 0.001 unit/mL and 0.003 unit/mL in uninduced and induced preparations, respectively. When whole cells of L. lactis harboring pNZBglBX10 were treated with ginseng extract, after permeabilization of cells by xylene, Rb1 and Rd were converted into Rg3(S) with a conversion yield of 61%. C-K was also produced by sequential reactions of the permeabilized cells harboring each pNZBgl and pNZBglBX10, resulting in a 70% maximum conversion yield. Conclusion: This study demonstrates that the lactic acid bacteria having specific ${\beta}$-glucosidase activity can be used to enhance the health benefits of Panax ginseng in either fermented foods or bioconversion processes.

• Microbiology and Biotechnology Letters
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• v.30 no.2
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• pp.116-122
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• 2002

The partial 165 rDNA sequences of 6 lactic acid bacterial strains isolated from Kimchi were determined. Two strains were Leuconostoc mesenteroides and the rest were incorrectly classified and turned out to be Lactobacillus. As the case of dairy lactic acid bacteria, the strains isolated from Kimchi also had cell-envelope proteinase (CEP) activity. As the result of partial CEP gene amplification with CEP-specific primers, the expected 1.2-kb amplificate was obtained not from Leu. mesenteroides but from Lactobacillus strains. The deduced amino acid sequence of PCR product amplified from the genomic DNA of Lactobacillus pentosus KFR1821 showed 95％ and 92％ homology with those of PrtPs from Lactococcus lactis subsp. cremoris and Lactobacillus paracasei subsp. paracasei, respectively. The PCR amplificate was used as a probe and the result of Southern hybridization illuminated the location of CEP gene in chromosomal DNA of Lb. pentosus KFR1821.

• Journal of Microbiology and Biotechnology
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• v.28 no.8
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• pp.1293-1298
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• 2018

Phosphomannomutase (ManB) converts mannose-6-phosphate (M-6-P) to mannose-1-phosphate (M-1-P), which is a key metabolic precursor for the production of GDP-D-mannose used for production of glycoconjugates and post-translational modification of proteins. The aim of this study was to express the manB gene from Escherichia coli in Lactococcus lactis subsp. cremoris NZ9000 and to characterize the encoded enzyme. The manB gene from E. coli K12, of 1,371 bp and encoding 457 amino acids (52 kDa), was cloned and overexpressed in L. lactis NZ9000 using the nisin-controlled expression system. The enzyme was purified by Ni-NTA column chromatography and exhibited a specific activity of 5.34 units/mg, significantly higher than that of other previously reported ManB enzymes. The pH and temperature optima were 8.0 and $50^{\circ}C$, respectively. Interestingly, the ManB used in this study had two substrate specificity for both mannose-1-phosphate and glucose-1-phosphate, and the specific activity for glucose-1-phosphate was 3.76 units/mg showing 70% relative activity to that of mannose-1-phosphate. This is the first study on heterologous expression and characterization of ManB in lactic acid bacteria. The ManB expression system constructed in this study canbe used to synthesize rare sugars or glycoconjugates.

• Animal Bioscience
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• v.35 no.2
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• pp.281-289
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• 2022

Objective: The aim of this study was to characterize the exopolysaccharides (EPS)-producing lactic acid bacteria from Taiwanese ropy fermented milk (TRFM) for developing a clean label low-fat fermented milk. Methods: Potential isolates from TRFM were selected based on the Gram staining test and observation of turbid suspension in the culture broth. Random amplified polymorphic DNA-polymerase chain reaction, 16S rRNA gene sequencing, and API CHL 50 test were used for strain identification. After evaluation of EPS concentration, target strains were introduced to low-fat milk fermentation for 24 h. Fermentation characters were checked: pH value, acidity, viable count, syneresis, and viscosity. Sensory evaluation of fermented products was carried out by 30 volunteers, while the storage test was performed for 21 days at 4℃. Results: Two EPS-producing strains (APL15 and APL16) were isolated from TRFM and identified as Lactococcus (Lc.) lactis subsp. cremoris. Their EPS concentrations in glucose and lactose media were higher than other published strains of Lc. lactis subsp. cremoris. Low-fat fermented milk separately prepared with APL15 and APL16 reached pH 4.3 and acidity 0.8% with a viable count of 9 log colony-forming units/mL. The physical properties of both products were superior to the control yogurt, showing significant improvements in syneresis and viscosity (p<0.05). Our low-fat products had appropriate sensory scores in appearance and texture according to sensory evaluation. Although decreasing viable cells of strains during the 21-day storage test, low-fat fermented milk made by APL15 exhibited stable physicochemical properties, including pH value, acidity, syneresis and sufficient viable cells throughout the storage period. Conclusion: This study demonstrated that Lc. lactis subsp. cremoris APL15 isolated from TRFM had good fermentation abilities to produce low-fat fermented milk. These data indicate that EPS-producing lactic acid bacteria have great potential to act as natural food stabilizers for low-fat fermented milk.

• Korean Journal of Veterinary Service
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• v.29 no.3
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• pp.277-285
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• 2006

Plasmids are covalently closed circular molecules of DNA that are stably inherited and replicate somewhat independently of the bacterial chromosome. Genes carried on plasmids can mediate a wide variety of important functions, including antibiotics (R plasmids) and heavy metals resistance, toxins production, cell penetration, iron chelation, complement resistance, and metabolic characteristics such as sucrose and lactose fermentation. Fifty strains of lactobacilli were isolated from 26 staters and 29 fermented milk products. They were classified 27 strains as Lactobacillus paracasei subsp paracasei, 11 stains as Lactococcus lactis subsp cremoris, 6 strains as L delbrueckii subsp lactis, 4 strains as L acidophius, and 2 strains as L delbrueckii subsp bulgaricus. All of these strains were examined for drug resistance and transferability of R plasmids. All of the isolates were sensitive to Am, C, CF, E, NB, P, T, and Te. But resistant to SXT 94% (47 strains), K 66% (33 strains), S 56% (28 strains), ENR 50% (25 strains), NOR 38% (19 strains) CIP 38% (19 strains), GM 16% (8 strains), and N 14% (7 strains), in order. And 32 different resistant patterns were found. The most frequently encountered patterns were CIP-ENR-K-NOR-S-SXT (5 strains). In vitro R plasmids transfer experiment, 57 antibiotic resistant strains which were not transfer to the recipient 2 Escherichia coli strains by conjugation, These results indicate that Lactobacillus in internal trade market' stater recognize R factor but transmissible R plasmid is not existed.

• Food Science and Biotechnology
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• v.18 no.5
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• pp.1279-1283
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• 2009

Garlic has been used for condiments and also for medicines to cure various diseases since ancient times. Many studies on the processing of garlic have been published, however, few of them were related with fermentation because of the antimicrobial action of the garlic. In this study, to conduct garlic fermentation, 4 lactic acid bacteria (LAB) strains with growth abilities in garlic medium were selected. Addition of various nitrogen, carbon, and mineral sources generally did not improve the growth of experimental strains during garlic fermentation except for Lactobacillus casei KFRI 704 by yeast extract and Lactococcus lactis subsp. cremoris ATCC 19257 by mineral sources. High performance liquid chromatography (HPLC) analysis of 32 phenolic compounds during fermentation showed that formononetin was decreased time dependently. The concentrations of volatile compounds and alliin did not change during fermentation. The results of this study would provide the basic understanding of garlic fermentation by selected strains of LAB.