• Korean journal of food and cookery science
• /
• v.29 no.3
• /
• pp.267-274
• /
• 2013

Demand for a rice cake, a popular traditional food in Korea, is rising, but its industrial-scale production is extremely difficult due to its short shelf-life caused by starch retrogradation and microbial spoilage. By means of the sourdough fermentation technique, we attempt to develop rice cakes with a longer shelf-life. Heterofermentative lactic acid bacteria (Weissella koreensis HO20, Weissella kimchii HO22) isolated from kimchi were used to ferment wet-milled rice flour for their abilities to produce exopolysaccharides and to inhibit the microbial spoilage of rice cakes. After 24 hr of fermentation at $25^{\circ}C$, viable cell counts in rice dough increased from $10^6$ CFU/g to $10^8$ CFU/g and total titratable acidity increased from 0.05% to 0.20%, whereas pH decreased from 6.5 to 5.1. Fermented rice flour showed significantly lower peak, trough, and final viscosities as well as breakdown and setback viscosities measured by rapid viscoanalyzer. Both lactic acid bacteria showed in vitro antifungal activity against Penicillium crustosum isolated from rice cakes. The antifungal activity remained constant after the treatments with heat, proteinase K and trypsin, but fell significantly by increase of pH. Rice cakes made of fermented rice flour were found to retard mycelial growth of P. crustosum. The degree of retrogradation as measured by the hardness of the rice cake was significantly reduced by the use of fermented rice flour. The results suggest that use of fermented rice flour has a beneficial role in retarding starch retrogradation and in preventing fungal growth, hence extending the shelf-life of rice cakes.

• Biomedical Science Letters
• /
• v.6 no.1
• /
• pp.1-9
• /
• 2000

To identity the genes responsible for the biosynthesis of exopolysaccharide, recombinant plasmids pUEX10 and pLEX10 were constructed from plasmid pLEX3 which was isolated from the recombinant cosmid library of Zoogloea ramigera 115. The complete nucleotide sequence of the 1.7 kb genomic DNA insert in plasmid pUEX10 was determined. Its analysis identified two open reading frames (ORF3 & ORF4) which could encode two proteins. The amino acid sequence derived from ORF3 showed the homology with gumC protein in Xanthomonas campestris as well as exoP protein in Rhizobium melizoti. The partial amino acid sequence of ORF4 showed the homology with polysaccharide export protein in Thermotoga maritima. Z. ramigera 115SLR and Z. ramigera 115SLR/pLEX10 showed the similar pattern for EPS production. Yield of exopolysaccharides produced by Z. ramigera 115SLR and Z. ramigera 115SLR/pLEX10 was 0.26% (w/v) and 0.16% (w/v), respectively.

• Food Science and Preservation
• /
• v.21 no.6
• /
• pp.903-907
• /
• 2014

For the selection of a starter for vinegar, six strains of acetic-acid bacteria were isolated from traditional Korean vinegar fermented through the static method. These strains were investigated for their acetic-acid fermentation and identification characteristics. The 16S rRNA sequences of six strains were identified as Acetobacter pasteurianus, A. malorum, Gluconacetobacter entanii, Ga. intermedius, and Ga. xylinus respectively. The overoxidation of acetic acid, acetic-acid and pH tolerances, and acetic-acid production of these strains were investigated. None seemed to have been overoxidized. The Gluconacetobacter genus showed acetic-acid tolerance. Among the acetic-acid bacteria, A. malorum V5-7 exhibited the highest pH tolerance. The Ga. intermedius V11-5 and Ga. xylinus V8-1 strains produced colloids that exopolysaccharides of fiber. The acetic-acid production by isolated acetic-acid bacteria and type strain was a achieved at a shaking culture at $30^{\circ}C$ for 5 days. A. malorum V5-7, A. pasteurianus Gam2, and Ga. intermedius V11-5 exhibited the highest acetic acid production. The study results indicate that appropriate strains of acetic-acid bacteria improved the thraditional Korean vinegar fermented through the static method.

• Journal of Microbiology and Biotechnology
• /
• v.30 no.4
• /
• pp.571-582
• /
• 2020

Quorum sensing (QS)-mediated infections cause severe diseases in human beings. The control of infectious diseases by inhibiting QS using antipathogenic drugs is a promising approach as antibiotics are proving inefficient in treating these diseases. Marine fungal (Pestalotiopsis sydowiana PPR) extract was found to possess effective antipathogenic characteristics. The minimum inhibitory concentration (MIC) of the fungal extract against test pathogen Pseudomonas aeruginosa PAO1 was 1,000 ㎍/ml. Sub-MIC concentrations (250 and 500 ㎍/ml) of fungal extract reduced QS-regulated virulence phenotypes such as the production of pyocyanin, chitinase, protease, elastase, and staphylolytic activity in P. aeruginosa PAO1 by 84.15%, 73.15%, 67.37%, 62.37%, and 33.65%, respectively. Moreover, it also reduced the production of exopolysaccharides (74.99%), rhamnolipids (68.01%), and alginate (54.98%), and inhibited the biofilm formation of the bacteria by 90.54%. In silico analysis revealed that the metabolite of P. sydowiana PPR binds to the bacterial QS receptor proteins (LasR and RhlR) similar to their respective natural signaling molecules. Cyclo(-Leu-Pro) (CLP) and 4-Hydroxyphenylacetamide (4-HPA) were identified as potent bioactive compounds among the metabolites of P. sydowiana PPR using in silico approaches. The MIC values of CLP and 4-HPA against P. aeruginosa PAO1 were determined as 250 and 125 ㎍/ml, respectively. All the antivirulence assays were conducted at sub-MIC concentrations of CLP (125 ㎍/ml) and 4-HPA (62.5 ㎍/ml), which resulted in marked reduction in all the investigated virulence factors. This was further supported by gene expression studies. The findings suggest that the metabolites of P. sydowiana PPR can be employed as promising QS inhibitors that target pathogenic bacteria.

• Journal of the Korean Society of Food Science and Nutrition
• /
• v.43 no.5
• /
• pp.749-755
• /
• 2014

Exopolysaccharides (EPSs) have been widely used in the food industry as viscofying, stabilizing, and emulsifying agents as well as in the pharmaceutical industry for their immunomodulatory, anti-tumor, and anti-inflammatory effects. A total of 458 lactic acid bacteria (LAB) strains isolated from several kinds of soybean pastes were screened for the production of homo-EPS (HoPS). LAB isolates were primarily screened using thin layer chromatography (TLC) and further screened polymerase chain reaction (PCR) targeting genes involved in HoPS production. Six LAB isolates producing high amounts of HoPS were identified by TLC. Among these isolates, glucansucrase gene was amplified in two strains (JSA57, JSB22), whereas the fructansucrase gene was detected in three strains (JSA57, JSB22, JSB66). After isolating the strains, their morphological characteristics and 16S rDNA sequences were determined. Six species were identified as L. alimentarius HSB15, L. plantarum JSA22, L. pentosus JSA57, L. brevis JSB22, L. alimentarius JSB66, and L. parabrevis JSB89. To evaluate the potential probiotic properties of these LAB, their survival rates against a simulated intestinal environment were determined. After 2 hr of incubation in artificial gastric juice, survival rates of JSA57, JSB90, JSB22, and JSB66 were all greater than 50%. After 2 hr of incubation in bile juice, viable cell count of JSB22 was similar with initial vial cell counts. Growth of the six LAB was screened in arabino-oligosaccharide (AOS)-containing MRS broth. Results showed that growth of the isolates selectively increased after culture in AOS-containing media. Strain JSB22 (6 hr), JSB66 (6 hr), HSB15 (20 hr), and JSA22 (29 hr) showed maximum growth rate. Especially, JSB22 showed the highest growth rate. These results suggest that EPS-producing LAB isolated from Deonjang could be applied as synbiotics.