• Journal of Ecology and Environment
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• v.41 no.9
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• pp.271-280
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• 2017

Background: Soil microorganisms play key roles in nutrient cycling and are distributed throughout the soil profile. Currently, there is little information about the characteristics of the microbial communities along the soil depth because most studies focus on microorganisms inhabiting the soil surface. To better understand the functions and composition of microbial communities and the biogeochemical factors that shape them at different soil depths, we analyzed microbial activities and bacterial and fungal community composition in soils up to a 120 cm depth at a fallow field located in central Korea. To examine the vertical difference of microbial activities and community composition, ${\beta}$-1,4-glucosidase, cellobiohydrolase, ${\beta}$-1,4-xylosidase, ${\beta}$-1,4-N-acetylglucosaminidase, and acid phosphatase activities were analyzed and barcoded pyrosequencing of 16S rRNA genes (bacteria) and internal transcribed spacer region (fungi) was conducted. Results: The activity of all the soil enzymes analyzed, along with soil C concentration, declined with soil depth. For example, acid phosphatase activity was $125.9({\pm}5.7({\pm}1SE))$, $30.9({\pm}0.9)$, $15.7({\pm}0.6)$, $6.7({\pm}0.9)$, and $3.3({\pm}0.3)nmol\;g^{-1}\;h^{-1}$ at 0-15, 15-30, 30-60, 60-90, and 90-120 cm soil depths, respectively. Among the bacterial groups, the abundance of Proteobacteria (38.5, 23.2, 23.3, 26.1, and 17.5% at 0-15, 15-30, 30-60, 60-90, and 90-120 cm soil depths, respectively) and Firmicutes (12.8, 11.3, 8.6, 4.3, and 0.4% at 0-15, 15-30, 30-60, 60-90, and 90-120 cm soil depths, respectively) decreased with soil depth. On the other hand, the abundance of Ascomycota (51.2, 48.6, 65.7, 46.1, and 45.7% at 15, 30, 60, 90, and 120 cm depths, respectively), a dominant fungal group at this site, showed no clear trend along the soil profile. Conclusions: Our results show that soil C availability can determine soil enzyme activity at different soil depths and that bacterial communities have a clear trend along the soil depth at this study site. These metagenomics studies, along with other studies on microbial functions, are expected to enhance our understanding on the complexity of soil microbial communities and their relationship with biogeochemical factors.

• Microbiology and Biotechnology Letters
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• v.40 no.3
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• pp.243-249
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• 2012

This study was conducted to screen an alginate-degrading microorganism and to investigate the characteristics of the alginate-degrading activity of its crude enzyme. A marine bacterium which produces extracellular alginate-degrading enzymes was isolated from the brown alga Sargassum thunbergii. 16S rRNA sequence analysis and physiological profiling resulted in the bacterium's identification as a Vibrio crassostreae strain, named Vibrio crassostreae PKA 1002. Its optimal culture conditions for growth were pH 9, 2% NaCl, $30^{\circ}C$ and a 24 hr incubation time. The optimal conditions for the alginate degrading ability of the crude enzyme produced by V. crassostreae PKA 1002 were pH 9, $30^{\circ}C$, a 48 hr incubation time and 8% alginic acid. The alginate degrading crude enzyme produced 3.035 g of reducing sugar per liter in 4% (w/v) alginate over 1 hr.

• Journal of Microbiology and Biotechnology
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• v.32 no.3
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• pp.294-301
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• 2022

In our greenhouse experiment, soil heat treatment groups (50, 80, and 121℃) significantly promoted growth and disease suppression of Panax notoginseng in consecutively cultivated soil (CCS) samples (p < 0.01), and 80℃ worked better than 50℃ and 121℃ (p < 0.01). Furthermore, we found that heat treatment at 80℃ changes the microbial diversity in CCS, and the inhibition ratios of culturable microorganisms, such as fungi and actinomycetes, were nearly 100%. However, the heat-tolerant bacterial community was preserved. The 16S rRNA gene and internal transcribed spacer (ITS) sequencing analyses indicated that the soil heat treatment had a greater effect on the Chao1 index and Shannon's diversity index of bacteria than fungi, and the relative abundances of Firmicutes and Proteobacteria were significantly higher than without heating (80 and 121℃, p < 0.05). Soil probiotic bacteria, such as Bacillus (67%), Sporosarcina (9%), Paenibacillus (6%), Paenisporosarcina (6%), and Cohnella (4%), remained in the soil after the 80℃ and 121℃ heat treatments. Although steam increased the relative abundances of most of the heat-tolerant microbes before sowing, richness and diversity gradually recovered to the level of CCS, regardless of fungi or bacteria, after replanting. Thus, we added heat-tolerant microbes (such as Bacillus) after steaming, which reduced the relative abundance of pathogens, recruited antagonistic bacteria, and provided a long-term protective effect compared to the steaming and Bacillus alone (p < 0.05). Taken together, the current study provides novel insight into sustainable agriculture in a consecutively cultivated system.

• Journal of Mushroom
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• v.21 no.3
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• pp.190-193
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• 2023

To cultivate pine mushroom (Tricholoma matsutake) artificially, co-cultivation with microorganisms has been introduced. Here, experiments were performed to assess the growth-promoting effect of bacteria on T. matsutake mycelia. Bacteria were isolated from soil samples collected in Yangyang County, Korea. Four of the bacterial isolates (Y22_B06, Y22_B11, Y22_B18, and Y22_B22) exhibited a growth-promoting effect on T. matsutake mycelia (154.67%, 125.91%, 134.06%, and 158.28%, respectively). To analyze the characteristics of the bacteria, especially the antifungal activity, 𝛼-amylase and cellulase activity assays were performed. In comparison with the controls, the isolated bacteria exhibited low 𝛼-amylase and cellulase activity. 16S rRNA gene sequencing was performed to identify the four bacterial isolates. The isolates belonged to the Terrabacteria group and were identified as Microbacterium paraoxydans, Paenibacillus castaneae, Peribacillus frigoritolerans, and P. butanolivorans. These bacterial isolates are expected to have contributed to the growth promotion of T. matsutake mycelia and the artificial cultivation of T. matsutake.

• Korean Journal of Microbiology
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• v.42 no.1
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• pp.40-46
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• 2006

Galactose joined to glucose by a $\beta(1\rightarrow4)$ glycosidic bond makes lactose and this disaccharide is rich in milk. It is known that lacotse is hydrolyzed to each monomeric sugar by either lactase in human or $\beta-galactosidase$ in bacteria. Ingestion of milk by lactase-deficient persons causes a temporary diarrhea and subsequent chronic diarrhea results in colitis with chronic inflammation. We isolated a $\beta-galactosidase$ producing psycrotolerant strain AS-20 from near cattle shed and investigated the growth at various temperature conditions. Whereas Escherichia coli strains did not grow at $10^{\circ}C$, the AS-20 strain could grow well at this low temperature and showed optimal growth at $30^{\circ}C$. The isolated strain was identified as 97% Hafnia alvei by biochemical properties. This strain could ferment glucose, lacotse, maltose, mannitol, xylose, ONPG, rhamanose and L-arabinose, and decarboxylate lysin and ornithine. To confirm the identity of isolated strain we amplified 16S rDNA by PCR and searched similarity of the 1426 bp DNA sequcence with Genbank database. The strain AS-20 showed 99% similarity with Hafnia alvei. The activity of $\beta-galactosidase$ was 1.5 times higher when the cell was grown at 10 or $20^{\circ}C$ than at $30^{\circ}C$. The highest enzyme activity of AS-20 was also much higher than that of E. coli, which was grown at $30^{\circ}C$.

• Transactions of the Korean hydrogen and new energy society
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• v.22 no.3
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• pp.326-332
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• 2011

The authors examined the effects of operating parameters on the $H_2$ production by dark fermentation of the wastewater generated from food waste recycling facilities, in short "food waste wastewater (FWW)". Central composite design based response surface methodology was applied to analyze the effect of initial pH (5.5-8.5) and substrate concentration (2-20 g Carbo. COD/L) on $H_2$ production. The experiment was conducted under mesophilic ($35^{\circ}C$) condition and a heat-treated ($90^{\circ}C$ for 20min)anaerobic digester sludge was used as a seeding source. Although there was a little difference in carbohydrate removal, $H_2$ yield was largely affected by the experimental conditions, from 0.38 to 1.77 mol $H_2$/mol $hexose_{added}$. By applying regression analysis, $H_2$ yield was well fitted based on the coded value to a second order polynomial equation (p = 0.0243): Y = $1.78-0.17X_1+0.30X_2+0.37X_1X_2-0.29X_1{^2}-0.35X_2{^2}$, where $X_1$, $X_2$, and Y are pH, substrate concentration (g Carbo. COD/L), and hydrogen yield (mol $H_2$/mol $hexose_{added}$), respectively. The 2-D response surface clearly showed a high inter-dependency between initial pH and substrate concentration, and the role of these two factors was to control the pH during fermentation. According to the statistical optimization, the optimum condition of initial pH and substrate concentration were 7.0 and 13.4 g Carbo. COD/L, respectively, under which predicted $H_2$ yield was 1.84 mol $H_2$/mol $hexose_{added}$. Microbial analysis using 16S rRNA PCR-DGGE showed that $Clostridium$ sp. such as $Clostridium$ $perfringens$, $Clostridium$ $sticklandii$, and $Clostridium$ $bifermentans$ were main $H_2$-producers.

• Korean Journal of Food Science and Technology
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• v.45 no.5
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• pp.571-577
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• 2013

Our aim was to ferment soymilk using lactic acid bacteria that showed protease activity and to optimize the condition for fermentation. In total, 108 strains of protease-producing lactic acid bacteria were isolated from various fermented foods such as kimchi and jeotgal, and among them, 29 strains displaying the highest protease activity were selected for further study. From these 29 strains, strain MK1, whose protease activity was 126 $mU/mL{\cdot}min$, was selected as the optimal fermentation strain owing to its high ability to digest soymilk protein. It was henceforth labeled as Lactobacillus paracasei MK1. The optimum conditions for the fermentation of soymilk by using L. paracasei MK1 were determined to be as follows: 30 h of fermentation time at a temperature of $30^{\circ}C$, and at a pH of 6.0 in the initial growth medium.

• The Korean Journal of Mycology
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• v.41 no.4
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• pp.248-254
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• 2013

A Gram-negative bacterium was isolated from mushroom media that markedly reduces the level of extracellular toxins (i.e., tolaasins) produced by Pseudomonas tolaasii, the most destructive pathogen of cultivated mushrooms. The HC1 strain was selected as detoxifying tolaasin by bioassay on potato and it was identified Pseudomonas sp. by the cultural, morphological and physiological characteristics, and analysis of the 16S rRNA. The isolated bacterium is saprophytic but not parasitic nor pathogenic to cultivation mushroom. The isolated bacterium for P. tolaasii cell, was sufficient for detoxification in vitro. Inoculation of the isolated bacterium prevents the development of bacterial disease in Pleurotus ostreatus, Flammunia velutipes and Agaricus bisporus. Control efficacy of brown blotch of strain HC1 treatment was 69, 68 and 55% on Agaricus bisporus, Flammulina velutipes and Pleurotus ostreatus, respectively. The suppressive bacterium may be useful in future for the development of biocontrol system and the construction of genetically modified edible fungi resistant to the disease caused by P. tolaasii.

• Asian-Australasian Journal of Animal Sciences
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• v.27 no.11
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• pp.1562-1570
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• 2014

The effects of Lactobacillus mucosae (L. mucosae), a potential direct fed microbial previously isolated from the rumen of Korean native goat, on the rumen fermentation profile of brewers grain were evaluated. Fermentation was conducted in serum bottles each containing 1% dry matter (DM) of the test substrate and either no L. mucosae (control), 1% 24 h broth culture of L. mucosae (T1), or 1% inoculation with the cell-free culture supernatant (T2). Each serum bottle was filled anaerobically with 100 mL of buffered rumen fluid and sealed prior to incubation for 0, 6, 12, 24, and 48 h from which fermentation parameters were monitored and the microbial diversity was evaluated. The results revealed that T1 had higher total gas production (65.00 mL) than the control (61.33 mL) and T2 (62.00 mL) (p<0.05) at 48 h. Consequently, T1 had significantly lower pH values (p<0.05) than the other groups at 48 h. Ammonia nitrogen ($NH_3$-N), individual and total volatile fatty acids (VFA) concentration and acetate:propionate ratio were higher in T1 and T2 than the control, but T1 and T2 were comparable for these parameters. Total methane ($CH_4$) production and carbon dioxide ($CO_2$) were highest in T1. The percent DM and organic matter digestibilities were comparable between all groups at all times of incubation. The total bacterial population was significantly higher in T1 (p<0.05) at 24 h, but then decreased to levels comparable to the control and T2 at 48 h. The denaturing gradient gel electrophoresis profile of the total bacterial 16s rRNA showed higher similarity between T1 and T2 at 24 h and between the control and T1 at 48 h. Overall, these results suggest that addition of L. mucosae and cell-free supernatant during the in vitro fermentation of dried brewers grain increases the VFA production, but has no effect on digestibility. The addition of L. mucosae can also increase the total bacterial population, but has no significant effect on the total microbial diversity. However, inoculation of the bacterium may increase $CH_4$ and $CO_2$ in vitro.

• Korean Journal of Agricultural Science
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• v.44 no.4
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• pp.558-565
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• 2017

This study was conducted to determine the effect of inoculation of microorganism isolated from pig feces on nutrient contents of fermented hulless barley. The microbial flora in feces of a total of four crossbred piglets ($Landrace{\times}Yorkshire{\times}Duroc$) was analyzed by 16s rRNA sequencing. The most abundant strain was then selected for fermentation of hulless barley. Lactobacillus plantarum (L. plantarum) was dominant (64.56%) in intestinal microbial flora in the pig feces. The selected candidate strain showed significantly higher survival rate at pH 7 than at pH 2.5 and 3.0 (p < 0.05). Incubated culture containing the candidate strain showed an increased growth rate with lower pH levels after 7.5 h incubation compared to initial incubation period (p < 0.05). When compared with commercial multiple probiotics which were used as control, the selected strain showed faster growth rate at 5 h post-incubation (p < 0.05). During the fermentation period, neither inoculated nor non-inoculated control hulless barley showed any change in pH value. Crude fat, fiber and ash contents were lower (p < 0.05) in hulless barley inoculated by the selected strain compared to control. However, moisture, energy, NDF and ADF were not affected by the inoculation of strain or fermentation period. Lactic acid was increased and acetic acid was decreased in the hulless barley inoculated with the selected strain during the fermentation period (p < 0.05). Taken together, our results suggest that L. plantarum derived from the pigs could be utilized as a new microorganism for manufacturing fermented feed stuffs.