• Journal of Microbiology and Biotechnology
• /
• v.34 no.6
• /
• pp.1239-1248
• /
• 2024

Peatlands are marginal agricultural lands due to highly acidic soil conditions and poor drainage systems. Drought stress is a big problem in peatlands as it can affect plants through poor root development, so technological innovations are needed to increase the productivity and sustainability of upland rice on peatlands. Rhizobacteria can overcome the effects of drought stress by altering root morphology, regulating stress-responsive genes, and producing exopolysaccharides and indole acetic acid (IAA). This study aimed to determine the ability of rhizobacteria in upland rice to produce exopolysaccharides and IAA, identify potential isolates using molecular markers, and prove the effect of rhizobacteria on viability and vigor index in upland rice. Rhizobacterial isolates were grown on yeast extract mannitol broth (YEMB) medium for exopolysaccharides production testing and Nutrient Broth (NB)+L-tryptophan medium for IAA production testing. The selected isolates identify using sequence 16S rRNA. The variables observed in testing the effect of rhizobacteria were germination ability, vigour index, and growth uniformity. EPS-1 isolate is the best production of exopolysaccharides (41.6 mg/ml) and IAA (60.83 ppm). The isolate EPS-1 was identified as Klebsiella variicola using 16S rRNA sequencing and phylogenetic analysis. The isolate EPS-1 can increase the viability and vigor of upland rice seeds. K. variicola is more adaptive and has several functional properties that can be developed as a potential bioagent or biofertilizer to improve soil nutrition, moisture and enhance plant growth. The use of rhizobacteria can reduce dependence on the use of synthetic materials with sustainable agriculture.

• Journal of the Korean Society of Food Science and Nutrition
• /
• v.38 no.12
• /
• pp.1773-1778
• /
• 2009

Guava (Psidium guajava L.) contains high amount of vitamins and minerals, and its leaves have been reported to be very effective on reducing blood pressure. In this study, antimicrobial characteristics of extracts from four different parts of guava (fruit, branch, leaf, and seed) with four different solvents (methanol, ethanol, acetone, and water) were evaluated. Four targeted food-borne microorganisms were selected; two Gram negatives (Escherichia coli O157:H7 and Salmonella Typhimurium) and two Gram positives (Staphylococcus aureus and Listeria monocytogenes). By the paper disc method, guava extracts showed stronger clear hollow zone against Gram positive bacteria than Gram negatives in nutrient broth agar plate. Especially, extracts of branches and leaves showed significant antibacterial activity. Guava extracts also showed significant inhibition activity on the growth of Gram positive food-borne bacteria in nutrient broth. For example, S. aureus did not grow at all at 200 ppm of acetone extracts of guava branch and leaf. In the case of L. monocytogenes, the same concentration of acetone extracts of guava branch and leaf inhibited the growth 33.5% and 55.4%, respectively, at 32 hrs of incubation time. The results indicated that extracts of guava branch and leaf showed significant antibacterial activities against food-borne Gram positive microorganisms, and that guava branches, the byproducts of guava, might be a valuable resource for antibacterial materials.

• Journal of Life Science
• /
• v.19 no.10
• /
• pp.1478-1483
• /
• 2009

A solid-state culture based on grain materials was attempted to produce a fibrinolytic enzyme for blood circulation improvement using Bacillus subtilis BK-17. The spore, rather than vegetative cell inoculation, of B. subtilis BK-17 on the solid-state culture was effective in the production of a fibrinolytic enzyme. Maximum spore production was obtained with a SFM medium (0.8% nutrient broth, 0.05% yeast extract, $10^{-1}$ M $MgCl_2$, $10^{-3}$ M $FeCl_3$, $10^{-4}$ $MnCl_2$, $10^{-5}$ M dipicolic acid, pH 6.5). Optimal pH and temperature were pH 6 and $30^{\circ}C$, respectively. The spore production reached a maximum at 60 hours of incubation. Bacillus subtilis BK-17 on the mung bean solid-state culture produced greater fibrinolytic activity, and less activity was seen in other grains such as kidney bean, soybean and corn. Protein and lipid contents of fermented soybeans were about 10 - 30% more than those of unfermented soybeans. Amino acid content was also 5 - 20% more than that of unfermented soybeans. These results indicated that fermented solid-state culture medium, fermented soybean in this case, can be utilized as a food supplement.

• Korean Journal of Microbiology
• /
• v.43 no.3
• /
• pp.201-209
• /
• 2007

The CFDA (6-carboxyfluorescein diacetate) direct viable count method and plate count (PC) method using conventional nutrient broth (NB) medium and $10^{-2}$ diluted NB (DNB) medium were applied to samples collected from Mt. Yongdoo In Andong, in an effect to determine the number of living bacteria pine mushroom forest soil. The number of living bacteria determined via plate count in NB medium comprised $5{\sim}8%$ of the CFDA direct viable count, and the bacteria in the DNB medium comprised $40{\sim}47%$. This result indicated that viable but nonculturable (VBNC) bacteria existed in the pine mushroom forest soil at a high percentage. The phylogenetic characteristics of the VBNC bacterial populations in the samples of pine mushroom (Tricholoma matsutake) forest soil were analyzed via the direct extraction of DNA and 16S rDNA-ARDRA. The 115 clones from pine mushroom forest soil were clustered into 31 different RFLP phylotypes by ARDRA. Based on the 16S rDNA sequences, the 31 ARDRA clusters were classified into 6 phylogenetic groups: ${\alpha}-,\;{\beta}-,\;{\gamma}-Proteobacteria$, Acidobacteria, Actinobacteria and Firmicutes. Among these bacterial populations, approximately 85% were classified as members of phylum Acidobacteria. The Acidobacteria phylum was shown to exist abundantly in the pine mushroom forest soil.

• Microbiology and Biotechnology Letters
• /
• v.33 no.3
• /
• pp.194-199
• /
• 2005

In oder to select an antifungal substance-producing antagonistic bacterium against Fusarium oxysporum casuing fusarium wilt on tomato, strain BK4 was isolated from local soil of Gyeoungbuk and was identified as Bacillus thuringiensis by 16s rDNA analysis, biochemical test, and Mcirolog TM 3.0 System. The antibiotic of B. thuringiensis BK 4 was highly produced at $30^{\circ}C$ in nutrient broth (pH 9.0). The crude antibiotic was even stable at $121^{\circ}C$ and more stable at slight alkalic condition than acid condition. It was also remained $50{\%}$ activity at pH 3.0. B. thuringiensis BK4 showed the inhibition of spore germination and the biocontrol ability against F. oxysporum causing fusarium wilt of tomato in vivo test. According to these results, B. thuringiensis BK4 was enough to use with a microbial agent for biocontrol against fusarium wilt.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.23 no.4
• /
• pp.297-302
• /
• 1990

This study was carried out to investigate the antimicrobial activity of the grapefruit seed extract (GFSE) The antimicrobial activity of GFSE was strong enough against such bacteria as Vibrio vulnificus, Vibrio fluvialis, Bacillus cereus, Staphylococcus aureus and Serratia sp. Growth of the above strains was inhibited by the GFSE'S concentration of 50 ppm. The growth of Vibrio vulnificus was completely inhibited by adding the 50 ppm GFSE to the nutrient broth medium with $3\%$ NaCl. The cell counts of Vibrio uulnfficus $5.2\times10^5$ at first in $5\%$ skim milk containing GFSE 0, 10, 30, 50 and 100 ppm were reduced to 35, 48, $5.6\times10^2,\;5.3\times10^3\;and\;9.6\times10^3/ml$ after 120 hours, respectively. And growth of Aspergillus Parasiticus, Asperillus versicolor, Penicillium funiculosum, Py-renochaeta terrestris and Trichoderma viride were inhibited by the concentration of GFSE 100, 50, 100, 10 and 30 ppm, respectively. The shelf life of Mulkimchi containing GFSE 50 and 100 ppm was 20 days longer than the control during storage at $5^{\circ}C\;and\;20^{\circ}C$.

• Korean Journal of Food Science and Technology
• /
• v.30 no.4
• /
• pp.823-826
• /
• 1998

It has been reported that alginic acid hydrolysate retains antimicrobial activity but the enzyme which hydrolyze alginic acid is not developed for industrial use. The authors developed chemical method for hydrolyzing alginic acid. For preparing alginic acid hydrolysate, equal quantity of alginic acid and ascorbic acid were added to water. Then the solution was heated at $121^{\circ}C$ for $20{\sim}30{\;}minutes$. The 4% solution of alginic acid hydrolysate was revealed relative viscosity 1.05, pH 3.2 and opaque whitish-yellow color. By addition of this hydrolysate to nutrient broth with the concentration of 0.1%, the growth of Bacillus sp. isolated from fish meat paste products was inhibited. The fish meat paste products containing 0.3% alginic acid hydrolysate prepared were prolonged their shelf life by 1 day stored at $30^{\circ}C$, 2 days at $20^{\circ}C$ and 4 days at $15^{\circ}C$.

• Particle and aerosol research
• /
• v.6 no.4
• /
• pp.185-192
• /
• 2010

This paper reports that the installation of a carbon fiber ionizer in front of an activated carbon fiber(ACF) filter enhanced the antibacterial efficiency. In addition, the effect of the ionizer on the filtration of bioaerosols is reported. Negative air ions from the ionizer were used as antibacterial agent. The test bacteria(Escherichia coli) were aerosolized using an atomizer and were deposited on the ACF filter media for 10 minutes. E. coli deposited on the filter were exposed to negative air ions for 0, 1, 5 and 10 minutes. Then they were separated from the ACF filter by shaking incubation with nutrient broth for 4 hours. The separated E. coli were spread on nutrient agar plates and incubated at $37^{\circ}C$ for 1~3 days. The antibacterial efficiency of E. coli was measured using a colony counting method. The antibacterial efficiencies of E. coli exposed to negative air ions for 1, 5 and 10 minutes were 14%, 48% and 71%, respectively. The filtration efficiency was evaluated by measuring the number concentration of bioaerosols at the upstream and downstream of the filter media. The increase of filtration efficiency by air ions was 14%, that is similar to the 17% filtration efficiency by none air ions. The ozone concentration was below the detection limit (under 0.01ppm) when the carbon fiber ionizers were on.

• Korean Journal Plant Pathology
• /
• v.1 no.1
• /
• pp.17-21
• /
• 1985

Microbial antagonism between virulent and avirulent isolates of Pseudomonas solanacearum was studied in relation to the control of bacterial wilt of tobacco. In nutrient broth media or in soil, the avirulent isolate of P. solanacearum grew faster than did the virulent one. Inhibitory effect of avirulent isolate against growth of virulent one was negligible in mixed culture of the two isolates. The disease severity of bacterial wilt was significantly reduced when the roots of cultivar BY 4 susceptible to bacterial wilt was dipped in suspension of an avirulent isolate for 6 hours prior to transplanting to the soil infested with virulent bacteria. When the seedlings of tobacco were poured with the suspension of an avirulent isolate onto the soil in pre-planting pots 24 hours before ransplanting, there was a significant reduction in disease severity in the field. However, the reduction was noticed until early July, but after middle of July, no difference between the avirulent isolate-treated and non-treated plants was found in severity of the bacterial wilt.

• Journal of Sericultural and Entomological Science
• /
• v.17 no.1
• /
• pp.55-62
• /
• 1975

In the studies of characterization of crystal prototoxin isolated from Bacillus thuringinensis var. alesti and its bioassay to the silkworm larvae, Bombyx mori L., the following results were obtained. 1. The complete lysis of bacteria grown on the nutrient agar at 30$^{\circ}C$ in an incubator took 30 days, but the period could be reduced by a half in a devised broth media in a fermentation jar. 2. The protein toxin extracted directly from a mixture of crystals and spores without separation of crystals and spores was pure as same as the protein toxin extracted from only crysals separated. 3. By SLS polyacrylamide gel electrophoresis of prototoxin released from crystals in alkali (pH 9.5) three different proteins in molecular weights of 120,000, 87,000, 74,000 were separated. 4. In the bioassay of the toxin to the silkworm larvae, LD$\sub$50/ per gram of the larvae in the 4th instar was 0.080 $\mu\textrm{g}$.