• Korean Journal of Environmental Biology
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• v.17 no.1
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• pp.59-69
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• 1999

Bacterial population, signal compounds of pollution, bacterial productivity, heterotrophic activity and the activities of extracellular enzymes were analyzed four times from July 1994 to April 1995 at Daejin, Galnam, Pohang, and Ulsan in the coastal area of Bast Sea in order to investigate the state of eutrophication. The population of heavy metal resistant bacteria in Pohang was the highest among all stations. The bacterial populations which could utilize C -P compounds (phosphonate) showed the highest at Pohang that was expected for the industrial and agricultural effluents to inpour. It could be useful as an index of expectation about the influx of industrial sewages and agricultural effluents. The activities of extracellular enzymes for the degradation of organic matter were the highest in the Ulsan Chuyongam, but low in Daejin. These results showed positive relationship with the population of heterotrophic bacteria and bacterial productivity The ratio of poly-P and DNA in Pohang was the highest, and that in Ulsan, Galnam, and Daejin consecutively, corresponding with the distribution of heterotrophic bacteria. In case of the heterotrophic activities, each of the stations gives difference of seasonal variation in heterotrophic activities. Bacterial productivity seemed to be dependent on seasons; the highest in summer and the lowest in fall and winter. These seasonal variations of bacterial productivity seems to be similar with those of heterotrophic bacteria. It is suggested that the state of eutrophication could be evaluated by the criteria of the population sizes and the productivities of microorganisms, the amount of poly-P, heterotrophic activity, the activities of extracellular enzymes, etc.

• Biomolecules & Therapeutics
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• v.31 no.1
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• pp.108-115
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• 2023

Numerous psychotropic and addictive substances possess structural features similar to those of β-phenethylamine (β-PEA). In this study, we selected 29 β-PEA derivatives and determined their structure-activity relationship (SAR) to their ability to inhibit dopamine (DA) reuptake; conducted docking simulation for two selected compounds; and identified their potential functionals. The compounds were subdivided into arylethylamines, 2-(alkyl amino)-1-arylalkan-1-one derivatives and alkyl 2-phenyl-2-(piperidin-2-yl)acetate derivatives. An aromatic group, alkyl group, and alkylamine derivative were attached to the arylethylamine and 2-(alkyl amino)-1-arylalkan-1-one derivatives. The inhibitory effect of the compounds on dopamine reuptake increased in the order of the compounds substituted with phenyl, thiophenyl, and substituted phenyl groups in the aromatic position; compounds with longer alkyl groups and smaller ring-sized compounds at the alkylamine position showed stronger inhibitory activities. Docking simulation conducted for two compounds, 9 and 28, showed that the (S)-form of compound 9 was more stable than the (R)-form, with a good fit into the binding site covered by helices 1, 3, and 6 of human dopamine transporter (hDAT). In contrast, the (R, S)-configuration of compound 28 was more stable than that of other isomers and was firmly placed in the binding pocket of DAT bound to DA. DA-induced endocytosis of dopamine D₂ receptors was inhibited when they were co-expressed with DAT, which lowered extracellular DA levels, and uninhibited when they were pretreated with compound 9 or 28. In summary, this study revealed critical structural features responsible for the inhibition of DA reuptake and the functional role of DA reuptake inhibitors in regulating D₂ receptor function.

• Journal of Mushroom
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• v.17 no.3
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• pp.85-92
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• 2019

Over a million tons of spent mushroom substrate (SMS) are generated as by-products of mushroom cultivation every year in Korea. Disposal of SMS by mushroom farmers is difficult, therefore, recycling solutions that do not harm the environment are necessary. SMS consists of mushroom mycelia and residues of fruiting bodies, containing a variety of bioactive substances, such as extracellular enzymes, antimicrobial compounds, and secondary metabolites. This paper reviews utility of SMS for bioremediation, controlling plant disease, and production of lignocellulytic enzymes, organic fertilizer, and animal feed.

• Membrane and Water Treatment
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• v.11 no.2
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• pp.159-166
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• 2020

In this study, the performance and antifouling properties of polysulfone (PSf) and polyvinylidene fluoride/polyvinylpyrrolidone (PVDF/PVP) membranes in a membrane bioreactor (MBR) were investigated. The membranes were prepared via phase inversion method, and then characterized by a set of analyses including contact angle, porosity and water flux and applied in a lab-scale MBR system. Soluble microbial product (SMP), extracellular polymeric substance (EPS), FTIR, gel permission chromatography (GPC) and particle size distribution (PSD) analyses were also carried out for MBR system. The results showed that the MBR with PSf membrane had higher hydrophobic organic compounds which resulted in formation of larger flocs in MBR. However, in this MBR had high compressibility coefficient of cake layer was higher (n=0.91) compared to MBR with PVDF/PVP membrane (n=0.8); hence, the fouling was more profound. GPC analysis revealed that compounds with molecular weight lower than 2 kDa are more formed on PSf membrane more than PVDF/PVP membrane. The results of FTIR analysis confirmed the presence of polysaccharide and protein compounds on the cake layer of both membranes which was in good agreement with EPS analysis. In addition, the results showed that their concentration was higher for the cake on PSf membrane.

• Microbiology and Biotechnology Letters
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• v.41 no.1
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• pp.70-78
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• 2013

Rhizoctonia solani and Fusarium oxysporum cause yield losses in numerous economically important crops. To develop a bio-control agent, cell free extracellular compounds (ECs) of 5 bacterial strains Burkholdria sp. L1, Pseudomonas sp. L4, Pseudomonas chlororaphis VN391, Bacillus subtilis VN21 and Enterobacter sp. VN99 from Vietnamese fields, which reduced levels of R. solani root rot in lettuces and F. oxysporum root rot in tomatoes, were investigated. In a growth chamber, ECs of all antagonists markedly enhanced the biomass of lettuces (10 to 14.1%) and tomatoes (11.38 to 13.88%). In greenhouses, the disease's severity on both crops treated with ECs of the antagonists was reduced significantly and biomass losses in the plants decreased markedly. The reduction level of R. solani root rot in lettuces was 75, 66.7, 50, and 16.7% by ECs of strains L1, L4, VN21 and VN391, respectively. The biomass of lettuces increased markedly by 29.13%, 21.67%, and 23.4% by ECs of strains L1, L4 and VN21, respectively. Similarly, the reduction levels of F. oxysporum root rot in tomatoes was 76.3, 75, 41.7 and 25% by ECs of strain L1, L4, VN21 and VN391, respectively, and the biomass was significantly enhanced by 14.42, 12.7 and 13%, respectively. The ECs of strain L1 exhibited the most effective bio-control agents to suppress R. solani and F. oxysporum.

• KSBB Journal
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• v.21 no.2
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• pp.85-89
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• 2006

Typical property of the white-rot fungi is their ability to degrade lignin and other aromatic compounds with non-specific extracellular enzyme. In this work, the modification of the strain(Funalia trogii ATCC 200800) and the culture condition was performed to enhance enzyme productivity. Single cell was separated by the protoplasts formation and several putative laccase and manganese peroxidase inducers were tested. By adopting the modified strain, enzyme productivity increased comparing with that of the original strain. Extracellular enzyme formation was highly stimulated by the addition of copper and various aromatic compounds in the glucose-based culture medium.

• Journal of Microbiology and Biotechnology
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• v.16 no.1
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• pp.5-14
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• 2006

Streptomycetes are Gram-positive microorganisms producing secondary metabolites through unique physiological differentiation [4]. The microbes show unusual morphological differentiation to form substrate mycelia, aerial mycelia, and arthrospores on solid medium [19]. Substrate mycelium growth is sustaining with sufficient nutrients in the culture medium. The concentration of a specific individual substrate in the culture environment is the most important extracellular factor allowing vegetative mycelia growth, where extracellular hydrolytic enzymes participate in the utilization of waterinsoluble substrates. However, with starvation of nutrients in the culture medium, the vegetative mycelia differentiate to aerial mycelia and spores. It has been considered that shiftdown of essential nutrients for mycelia growth is the most important factor triggering morphological and physiological differentiation in Streptomyces spp. Since proteineous macromolecule compounds are the major cellular components, these are faced to endogenously metabolize following a severe depletion of nitrogen source in culture nutrients (Fig. 1). Various proteases were identified of which production was specifically related with the phase of mycelium growth and also morphological differentiation. The involvement of proteases and protease inhibitor is reviewed as a factor explaining the mycelium differentiation in Streptomyces spp.

• Journal of Microbiology and Biotechnology
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• v.17 no.6
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• pp.897-904
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• 2007

The aim of this paper is to discuss the methodology of our investigation of the dynamics of protein degradation and the total in situ protealytic activity in meso/eutrophic, eutrophic, and hypereutrophic freshwater environments. Analysis of the kinetics and rates of enzymatic release of amino acids in water samples preserved with sodium azide allows determination of the concentrations of labile proteins $(C_{LAB})$, and their half-life time $(T_{1/2})$. Moreover, it gives more realistic information on resultant activity in situ $(V_{T1/2})$ of ecto- and extracellular proteases that are responsible for the biological degradation of these compounds. Although the results provided by the proposed method are general y well correlated with those obtained by classical procedures, they better characterize the dynamics of protein degradation processes, especially in eutrophic or hypereutrophic lakes. In these environments, processes of protein decomposition occur mainly on the particles and depend primarily on a metabolic activity of seston-attached bacteria. The method was tested in three lakes. The different degree of eutrophication of these lakes was clearly demonstrated by the measured real proteolytic pattern and confirmed by conventional trophic state determinants.

• Journal of Korean Society on Water Environment
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• v.23 no.6
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• pp.993-997
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• 2007

The upflow anaerobic sludge blanket (UASB) reactor can be effective for treating simple organic compounds containing high concentration of ammonia nitrogen. The chemical oxygen demand (COD) removal efficiency was about 80% at ammonia nitrogen concentration up to 6,000 mg-N/L. This result also showed that it would be possible to treat propionate effectively at free ammonia nitrogen concentration up to 724 mg-N/L if sufficient time was allowed for adaptation. However the specific methanogenic activity (SMA) of granule was lower than that of granule in the reactor with lower ammonia nitrogen concentration. At 8,000 mg-N/L, the inhibition of high ammonia concentration was observed with evidence of increase of the volatile suspended solids (VSS) concentration in the effluent. It might be ascribed to the decrease in the content of extracellular polymer (ECP), which resulted to the sloughing off of obligated proton-reducing acetogens and heterogenotrophic methanogens from the exterior of granular sludge. This caused a great portion of the finely sludge to be easily washed out. Therefore, failure to maintain the balance between these two groups of microorganism cause accumulation of the hydrogen partial pressure in the reactor, which could have inhibited the growth of acetate utilizing methanogens.

• Journal of Microbiology and Biotechnology
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• v.27 no.7
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• pp.1316-1323
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• 2017

Geosmin and 2-methylisoborneol (2-MIB), responsible for earthy or musty smell, are a major concern for safe drinking water supplies. This study investigated the effects of environmental factors on odorous compound production and cell growth in cyanobacterial strains. Anabaena sp. FACHB-1384, a 2-MIB producer, was sensitive to low temperature (<$20^{\circ}C$). However, geosmin producers, Anabaena sp. Chusori and Anabaena sp. NIER, were sensitive to high light intensity (>$100{\mu}mol/m^2/sec$), but not to low temperature. Geosmin concentrations increased under higher nitrate concentrations, being linearly proportional to cell density. A P-limited chemostat showed that P-stress decreased the geosmin productivity and extracellular geosmin amount per cell in Anabaena sp. NIER. However, only 2-MIB productivity was reduced in Planktothrix sp. FACHB-1374 under P-limitation. The extracellular 2-MIB amount per cell remained constant at all dilution rates. In conclusion, high light intensity and P-stress can contribute to the lower incidence of geosmin, whereas 2-MIB reduction could be attainable at a lower temperature.