• KSBB Journal
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• v.23 no.1
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• pp.18-22
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• 2008

Various probiotic Lactobacillus spp. are known to produce exopolysaccharide (EPS) which has potential health promoting functionality. A Lactobacillus paracasei strain producing EPS was isolated from healthy human. This strain, named L. paracasei KLB58, was grown on modified MRS medium. Experiments were conducted under various growth conditions to optimize the EPS production. Our study showed that incubation temperature played an important role in EPS production. When incubation temperature was changed from $37^{\circ}C$ to $25^{\circ}C$, the increase of EPS production (28.1 mg/ml) was the highest in our experiment. The type of carbon source in the medium also affected EPS production. Galactose was the most effective for EPS production among the carbon sources examined. Using galactose, glucose, lactose and sucrose, the amount of released EPS was 38.9 mg/ml, 35.6 mg/ml, 21.76 mg/ml and 16.9 mg/ml, respectively. However, acidity in growth medium inhibited EPS productivity due to the low growth yield. When grown at pH 4, L. paracasei KLB58 could only produce EPS of 14.6 mg/ml. When the initial amounts of nitrogen and carbon sources were examined, EPS production was not significantly affected by nitrogen source while carbon source affected considerably.

• Food Engineering Progress
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• v.14 no.3
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• pp.208-216
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• 2010

Lab scale experiments were conducted in order to assess the applicability of $CaCO_{3}$-alginate beads as neutralizer for the high cell density cultivation and prepare the direct vat inoculation cultures of isolated sourdough lactic acid bacteria. With increasing the amount of bead and decreasing the diameter of bead in acidic solution, the neutralizing effect of $CaCO_{3}$-alginate bead became higher. In batch process with $CaCO_{3}$-alginate beads, Lactobacillus amylovorus DU-21 isolated from sourdough showed the highest viable cell counts and optical density in MRS broth. The values of viable cell counts and optical density were 9.996 log CFU/mL and 3.97, respectively. Experiments on the conditions which increase viability during lyophilization were carried out and the following results were obtained; 15% glycerol revealed the high cryoprotective effect on the concentrated cultures during lyophilization among the two cryoprotective agents. Consequently, $CaCO_{3}$-alginate beads and 15% glycerol were found to be useful not only to cultivate Lactobacillus amylovorus DU-21 but also to preserve strain.

• Microbiology and Biotechnology Letters
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• v.41 no.2
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• pp.190-197
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• 2013

Three slime-forming lactic acid bacteria were isolated from traditional Korean fermented soy sauce and soybean paste and shown to produce exopolysaccharides (EPS) in sucrose media. By isolating the strains, examining their morphological characteristics and determining their 16S rDNA sequences, N58-5 and K6-7 were identified as Leuconostoc mesenteroides and N45- 10 as Leuconostoc citreum. The acid and bile tolerances of these three strains were investigated. Amongst the three lactic acid bacteria, Leuc. citreum N45-10 exhibited the highest viability ($10^5-10^6$ CFU/ml) in 0.05 M sodium phosphate buffer (pH 0.3) for 2 h, in artificial gastric juice for 2 h and in 0.3%, 0.5% oxgall for 24h. Leuc. mesenteroides K6-7, N58-5 and Leuc. citreum N45- 10 were grown in sucrose liquid medium and 8.16 g/L, 3.65 g/L, 16.17 g/L of EPS was collected, respectively. The hydrolyzed EPS was analyzed by HPLC in order to determine the sugar composition of EPS. Leuc. mesenteroides K6-7 and N58-5 showed two peaks indicating glucose and fructose, thus they were determined to be hetero-type polysaccharides. Leuc. citreum N45-10 showed only the glucose polymer, indicating it to be a homo-type polysaccharide. In addition, all three lactic acid bacterial hemolysis did not demonstrate a clear zone in blood agar in the area surrounding a lactic acid bacteria colony.

• Microbiology and Biotechnology Letters
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• v.20 no.5
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• pp.519-526
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• 1992

The gene coding for urease of alkalophilic Bacillus pasteurii had been cloned in Escherichia coli previously. The urease protein was purified 63.1-fold by TEAE-cellulose, DEAE-Sephadex A-50, Sephadex G-150 and Sephadex G-200 chromatographies with a 7.3% yield from the sonicated fluid of the E. coli HB1Ol(pBUll) encoding B. pasteurii urease gene. The ureases of E. coli (pBUll) and B. pasteurii possessed as a $K_m$ for urea, 42.1 mM and 40.4 mM, respectively. They hydrolyzed urea with $V_{max}$ of 86.9$\mu$mol/min and 160$\mu$mol/min, respectively. Both ureases were composed with four subunits (Mrs 67,000) and a subunit (Mr 20,000). The molecular weight of both native enzymes was Mr 280,OOO$pm$10,000 determined by gel filtration chromatography and Coomassie blue staining of the subunits. The optimal reaction pH of both ureases were pH 7.5. The ureases were stabled in pH 5.5-10.5. The optimal reaction temperature of both ureases were $60^{\circ}C$, and the ureases were stable for an hour at $50^{\circ}C$, 40min at $60^{\circ}C$ and 10 min at $70^{\circ}C$ The activity of both enzymes were inhibited completely by $Ag^{2+}$, $Hg^{2+}$, $Zn^{2+}$, $Cu^{2+}$, and were inhibited 60% by CoH, 30% by $Fe^{2+}$ and 10% by $Pb^{2+}$. However it was increased by the addition of $Sn^{2+}$, $Mn^{2+}$, $Mg^{2+}$ at concentration of $1{\times}10^{-3}$M. Both ureases were inhibited completely by p-CMB and acetohydroxamic acid. The urease expressed in E. coli (pBU11) was inhibited 70% by SDS. The urease of B. pasteurii was inhibited 40% by hydroxyurea, whereas the recombinant urease of E. coli strain was inhibited 17%. Both enzymes were not inhibited by cyclohexanediaminetetraacetic acid (CDTA) and ethylendiaminetetraacetic acid (EDTA).

• Investigative Magnetic Resonance Imaging
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• v.3 no.1
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• pp.47-52
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• 1999

Purpose : The purpose of this study was aimed to evaluate the BOLD(blood oxygen level dependent) contrast fMRI(functional MR imaging) in the occipital lobe and to compare with the metabolic changes based on H MRS (MR spectroscopy) and MRSI (MR spectroscopic imaging) before and after visual stimulation Materials and Methods : Healthy human volunteers (eight males and two females with 24-30 year age) participated in this study. All of the BOLD fMRI were acquired on a 1.5T MR with EPI during supervised visual stimulation in the occipital lobe. The red flicker with 8Hz was used for visual stimulation. After imaging acquisition, the MR images were transferred into unix workstation and processed with acquired from the same location based on the activation map. MRSI (magnetic resonance spectroscopic imaging) was also acquired to analyze the lactate changes before and after stimulation. Results : The activation maps were successfully produced by BOLD effect due to visual stimulation. NAA (N-acetyle aspartate)/Cr (creatine) ratio varied only from $1.79{\pm}0.28{\;}to{\;}1.88{\pm}0.20$ in activation area before and after stimulation. However, the signal intensity of lactate was elevated $9.48{\pm}4.38$ times higher than before activation. Lactate metabolite images were consistent with the activation maps. Conclusion : The BOLD contrast fMRI is enough sensitive to detect the activated area in human brain during the visual stimulation. Lactate metabolite map presents the evidence of lactate elevation on the same area of activation.