ABSTRACT: Aims: To establish an efficient genetic transformation protocol for Leuconostoc species, methods for competent-cell preparation and electroporation conditions were optimized. Methods and Results: Leuconostoc mesenteroides subsp. mesenteroides ATCC8293 cells were sequentially treated with penicillin G and lysozyme, and the plasmid pLeuCM was subsequently transformed into the cells. Our results demonstrated that transformation efficiencies were significantly increased (100-fold), and increased electric field strength also contributed to enhance transformation efficiency. Maximum transformation efficiency (1 × 10(4) or more transformants per μg DNA) was achieved when cells were grown in De Man, Rogosa, Sharpe (MRS) media containing 0·25 mol l(-1) sucrose and 0·8 μg ml(-1) penicillin G, followed by treatment with 600 U ml(-1) lysozyme and electroporation at a field strength of 10 kV cm(-1) . When this protocol was used to transform pLeuCM into Leuc. mesenteroides, Leuconostoc gelidum, Leuconostoc fallax and Leuconostoc argentinun, successful transformations were obtained in all cases. Furthermore, this procedure was applicable to species belonging to other genera, including Lactobacillus plantarum, Pediococcus pentosaceus and Weissella confusa. Conclusions: The results demonstrate that the transformation efficiency for Leuconostoc spp. could be increased via optimization of the entire electroporation procedures. Significance and Impact of the Study: These optimized conditions can be used for the extensive genetic study and the metabolic engineering of not only Leuconostoc spp. but also different species of lactic acid bacteria.
Letters in Applied Microbiology 08/2012; 55(4):314-21. · 1.62 Impact Factor
ABSTRACT: The aim of this study was to elucidate the Korean consumers’ aroma preference on wines. For this, a sensory test on 6 commercial
red wines (5 imported and 1 domestic) was conducted by 250 panels and the volatile compounds of those wines were analyzed
by gas chromatography-mass spectrometry. Sample 1 obtained the highest mean aroma acceptability score and analysis of volatile
compounds revealed that it retained many kinds of esters and alcohols compared to other wines (including 2 acetate esters,
6 ethyl esters, 3 other esters, and 5 alcohols, mostly giving fruity aroma). Sample 1 was made by blending 2 varieties of
grapes and this brewing technology might give a preferred aroma balance. The domestic wine, sample 2, made of ‘Campbell Early’
grape earned relatively higher acceptability score (2nd ranked), being considered its strong grape aroma. In the lower score group, higher concentrations of isoamyl alcohol, 1-isothiocyanto-propane,
and volatile phenol were detected and their strong grassy or fatty odor might affect the lower sensory result. Strategies
for production of consumer-preferred wines were suggested.
Keywordswine-volatile compound-sensory test-‘Cabernet Sauvignon’-‘Campbell Early’
Food science and biotechnology 04/2012; 19(1):43-49. · 0.49 Impact Factor
ABSTRACT: To investigate possible recycling of a brine solution for the production of salted cabbage (jeolimbaechu), bacterial cell counts in the brine solution and salted cabbages were measured after repeated salting processes. After a
salting process with a 13% brine solution for 15 hr at 10°C, the salt concentration in brine and salted cabbage decreased
to 9.0–9.9 and 1.5–3.2% (depending on parts), respectively. After 5 repetitions, the total microbial count in the brine solution
and salted cabbage gradually increased to 8.9 and 8.7 log CFU/g, respectively. Polymerase chain reaction-denaturing gradient
gel electrophoresis (PCRDGGE) showed that the marine bacteria, Pseudoalteromonas sp. and Halomonas sp. appeared from the 3rd batch; their intensities increased steadily and dominated the recycled brine solution. Meanwhile, Lactobacillus sakei found in the cabbage during the first salting process decreased with successive repetitions. These results show a high risk
of marine microbial contamination in salted cabbage when the brine solution is re-used. Therefore, to re-use brine solution,
application of proper inhibitory methods to prevent microbial cell growth in the brine solution is required.
Food science and biotechnology 04/2012; 20(1):223-227. · 0.49 Impact Factor
ABSTRACT: A polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) method was used to determine the presence and
diversity of lactic acid bacteria (LAB) in takju, a traditional Korean rice wine. Bacterial DNAs were extracted from 15 commercial rice wines and amplicons of partial 16S
rRNA genes were separated by DGGE and intense bands were sequenced. Lactobacillus (Lb.) paracasei, Lb. plantarum, and Leuconostoc pseudomesenteroides were detected in all samples and Lb. harbinensis and Lb. parabuchneri were found with above 80% frequency of occurrence. Unknown species of Lactobacillus were also widely detected. This result revealed that, regardless of products and raw materials, the distribution profiles
of LAB in takju products have a common pattern comprising of above predominant species and, furthermore, takju can be regarded as a LAB-rich fermented food providing various probiotics.
Keywords16S rRNA gene-lactic acid bacteria-polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE)-
Food science and biotechnology 04/2012; 19(3):749-755. · 0.49 Impact Factor
ABSTRACT: This study investigates the buffering effects of calcium salts in kimchi on total acidity, microbial population, and dextransucrase activity. Calcium chloride or calcium carbonate was added in dongchimi-kimchi, a watery-radish kimchi, and their effects on various biochemical attributes were analyzed. The addition of 0.1% calcium chloride produced a milder decrease in the pH after 24 days of incubation, which allowed the lactic acid bacteria to survive longer than in the control. In particular, the heterofermentative Leuconostoc genus population was 10-fold higher than that in the control. When sucrose and maltose were also added along with the calcium salts, the dextransucrase activity in the kimchi was elevated and a higher concentration of isomaltooligosaccharides was synthesized when compared with the control. Calcium chloride was determined as a better activator compound of dextransucrase than calcium carbonate, probably because of its higher solubility. Therefore, the results of this study confirm the ability of the proposed approach to modulate the kimchi fermentation process and possibly enhance the quality of kimchi based on the addition of dietary calcium salts.
Journal of Microbiology and Biotechnology 12/2009; 19(12):1644-9. · 1.38 Impact Factor
ABSTRACT: D-form lactate is often found in fermented foods and excessive dietary intake of D-lactate may cause metabolic stress in both infants and patients. Leuconostoc citreum is a major lactic acid bacterium that produces D-lactate in fermented foods. The aim of this study was to change the pyruvate carbon flux in L. citreum from D-lactate into L-lactate by heterologous expression of L-lactate dehydrogenase (ldhL) gene. For this, ldhL from Lactobacillus plantarum was cloned and introduced into L. citreum using a shuttle vector pLeuCM. In the transformant, ldhL was successfully transcribed and L-lactate dehydrogenase was expressed. As a consequence of transformation, the ratio between D- and L-isomers was changed due to the increment of L-lactate and the decrement of D-lactate, but no significant differences were found in total lactate concentration between the host and transformant cells. This is the first report of metabolic engineering in Leuconostoc by modulating the central carbon flux into health-favored way.
Journal of biotechnology 09/2009; 144(2):160-4. · 2.88 Impact Factor