• Journal of Life Science
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• v.29 no.1
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• pp.135-145
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• 2019

Zymomonas mobilis has been recognized as a potential industrial ethanologen for many decades due to its outstanding fermentation characteristics, including high ethanol tolerance, fast sugar uptake rate, and high theoretical ethanol yield. With the emergence of the postgenomic era and the recent announcement of DuPont's world largest cellulosic ethanol production process, research on this bacterium has become even more important to harness successful application not only for use in the bioethanol process but also in other biochemical processes, which can be included in bio-refinery. As an important industrial microorganism, Z. mobilis will likely be exposed to various stressful environments, such as toxic chemicals, including the end-product ethanol and fermentative inhibitory compounds (e.g., furan derivatives, organic acids, and lignin derivatives in pretreatment steps), as well as physical stresses, such as high temperature during large-scale ethanol fermentation. This review focuses on recent information related to the industrial robustness of this bacterium and strain development to improve the ethanol yield and productivity in the lignocellulosic ethanol process. Although several excellent review articles on the strain development of this bacterium have been published, this review aims to fill gaps in the literature by highlighting recent advances in physiological understanding of this bacterium that may aid strain developments and improve the ethanol productivity for lignocellulosic biomass.

• Journal of Microbiology and Biotechnology
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• v.31 no.5
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• pp.756-763
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• 2021

Agarose is a linear polysaccharide composed of ᴅ-galactose and 3,6-anhydro-ʟ-galactose (AHG). It is a major component of the red algal cell wall and is gaining attention as an abundant marine biomass. However, the inability to ferment AHG is considered an obstacle in the large-scale use of agarose and could be addressed by understanding AHG catabolism in agarolytic microorganisms. Since AHG catabolism was uniquely confirmed in Vibrio sp. EJY3, a gram-negative marine bacterial species, we investigated AHG metabolism in Streptomyces coelicolor A3(2), an agarolytic gram-positive soil bacterium. Based on genomic data, the SCO3486 protein (492 amino acids) and the SCO3480 protein (361 amino acids) of S. coelicolor A3(2) showed identity with H2IFE7.1 (40% identity) encoding AHG dehydrogenase and H2IFX0.1 (42% identity) encoding 3,6-anhydro-ʟ-galactonate cycloisomerase, respectively, which are involved in the initial catabolism of AHG in Vibrio sp. EJY3. Thin layer chromatography and mass spectrometry of the bioconversion products catalyzed by recombinant SCO3486 and SCO3480 proteins, revealed that SCO3486 is an AHG dehydrogenase that oxidizes AHG to 3,6-anhydro-ʟ-galactonate, and SCO3480 is a 3,6-anhydro-ʟ-galactonate cycloisomerase that converts 3,6-anhydro-ʟ-galactonate to 2-keto-3-deoxygalactonate. SCO3486 showed maximum activity at pH 6.0 at 50℃, increased activity in the presence of iron ions, and activity against various aldehyde substrates, which is quite distinct from AHG-specific H2IFE7.1 in Vibrio sp. EJY3. Therefore, the catabolic pathway of AHG seems to be similar in most agar-degrading microorganisms, but the enzymes involved appear to be very diverse.

• Journal of Microbiology and Biotechnology
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• v.31 no.2
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• pp.290-297
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• 2021

Leptolyngbya sp. KIOST-1 (LK1) is a newly isolated cyanobacterium that shows no obvious cytotoxicity and contains high protein content for both human and animal diets. However, only limited information is available on its toxic effects. The purpose of this study was to validate the safety of LK1 powder. Following Organisation for Economic Co-operation and Development (OECD) guidelines, a single-dose oral toxicity test in Sprague Dawley rats was performed. Genotoxicity was assessed using a bacterial reverse mutation test with Salmonella typhimurium (strains TA98, TA100, TA1535, and TA1537) and Escherichia coli WP2 uvrA, an in vitro mammalian chromosome aberration test using Chinese hamster lung cells, and an in vivo mammalian erythrocyte micronucleus test using Hsd:ICR (CD-1) SPF mouse bone marrow. After LK1 administration (2,500 mg/kg), there were no LK1-related body weight changes or necropsy findings. The reverse mutation test showed no increased reverse mutation upon exposure to 5,000 ㎍/plate of the LK1 powder, the maximum tested amount. The chromosome aberration test and micronucleus assay demonstrated no chromosomal abnormalities and genotoxicity, respectively, in the presence of the LK1 powder. The absence of physiological findings and genetic abnormalities suggests that LK1 powder is appropriate as a candidate biomass to be used as a safe food ingredient.

• The Korea Journal of Herbology
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• v.32 no.6
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• pp.1-7
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• 2017

Objectives : The heartwood of Sappan Lignum has been used since ancient times as an ingredient in folk medicines against anti-bacterial and anti-anemia purposes. Many bioactive constituents have been derived from this biomass such as chalcones and homoisoflavonoids. In the current investigation, the antioxidant and anti-diabetic properties using DPPH and $ABTS^+$ radicals scavenging, ${\alpha}-glucosidase$, and advanced glycation end products (AGEs) inhibition assays were evaluated by different extraction methods of Sappan Lignum. Methods : In our continuing investigation for bioactive natural ingredients, the antioxidant and ${\alpha}-glucosidase$ inhibitory properties of Sappan Lignum extracts were prepared from different extraction methods and the biological efficacies were investigated in vitro. The antioxidant properties were evaluated employing radical scavenging assays using 1,1-diphenyl-2-picrylhydrazyl (DPPH) and 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulphonic acid) ($ABTS^+$) radicals. In addition, the anti-diabetic effects of Sappan Lignum extracts were tested via ${\alpha}-glucosidase$ and AGEs formation inhibitory assay. The total phenolic contents were determined using a spectrophotometric method. Results : All the tested samples showed dose-dependent radical scavenging and ${\alpha}-glucosidase$ inhibitory activities. Among the tested extracts, the 80% methanolic extract of Sappan Lignum was showed the most potent activity with an $IC_{50}$ value of $82.3{\pm}1.7{\mu}g/m{\ell}$ against DPPH radical scavenging assay. While, $ABTS^+$ radical scavenging activity of 80% methanolic extract was higher than those of other extracts. Also, ${\alpha}-glucosidase$ inhibitory and AGEs formation effects of each extacts and total phenolic contents were evaluated. Conclusions : These results suggested that Sappan Lignum can be considered as a new effective source of natural antioxidant and anti-diabetic materials.

• Membrane and Water Treatment
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• v.14 no.1
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• pp.35-45
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• 2023

Biofilms significantly affect the performance of wastewater treatment processes in which biodegradability of numerous microorganisms are actively involved, and various technologies have been applied to secure microbial biofilms. Understanding changes in biofilm characteristics by regulating expression of signaling molecules is important to control and regulate biofilms in membrane bioreactor, i.e., biofouling. This study investigated effects of addition of acyl-homoserine lactones (AHL) as a controllable factor for the microbial signaling system on biofilm formation of Pseudomonas aeruginosa PAO1 and multiple strains in membrane bioreactor. The addition of three AHL, i.e., C4-, C6-, and C8-HSL, at a concentration of 200 ㎍/L, enhanced the formation of the PAO1 biofilm and the degree of increases in the biofilm formation of PAO1 were 70.2%, 76.6%, and 72.9%, respectively. The improvement of biofilm formation of individual strains by C4-HSL was an average of 68%, and the microbial consortia increased by approximately 52.1% in the presence of 200 ㎍/L C4-HSL. CLSM images showed that more bacterial cells were present on the membrane surface after the AHL application. In the COMSTAT results, biomass and thickness were increased up to 2.2 times (PAO1) and 1.6 times (multi-strains) by C4-HSL. This study clearly showed that biofilm formation was increased by the application of AHL to individual strain groups, including PAO1 and microbial consortia, and significant increases were observed when 50 or 100 ㎍/L AHL was administered. This suggests that AHL application can improve the biofilm formation of microorganisms, which could yield an enhancement in efficiency of biofilm control, such as in various biofilm reactors including membrane bioreactor and bioflocculent systems in water/wastewater treatment processes.

• Journal of Mushroom
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• v.20 no.3
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• pp.163-167
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• 2022

Bio-based alternative leathers may be produced from biomass fiber, protein polymers, bacterial cellulose, and mushroom mycelia. Of these components, mushroom mycelia are of greatest interest. In this study, the potential of Fomes fomentariusas a mushroom mycelial mat was confirmed, and the optimal strain for the development of the mycelial mat was determined. Moreover, the quality of the mycelial mat was improved by identifying an efficient culture method to increase productivity. Mutant strains whose independence was verified were obtained by treatment with gamma irradiation under various conditions. Biofilm formation by the resulting strains was examined in sawdust and liquid media and the characteristics of the biofilms were analyzed. The biofilm of the mutant strains showed results that were similar to or better than the biofilms of longevity and cypress mushrooms. These findings are expected to be utilized in future research aimed at discovering new biomaterials using mushroom mycelia.

• Microbiology and Biotechnology Letters
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• v.51 no.3
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• pp.257-267
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• 2023

The potential polyhydroxyalkanoates (PHA)-producing bacteria, Bacillus megaterium PP-10, was successfully isolated and studied its feasibility for utilization of pineapple peel waste (PPW) as a cheap carbon substrate. The PPW was pretreated with 1% (v/v) H₂SO₄ under steam sterilization and about 26.4 g/l of total reducing sugar (TRS) in pineapple peel hydrolysate (PPH) was generated and main fermentable sugars were glucose and fructose. A maximum cell growth and PHA concentration of 3.63 ± 0.07 g/l and 1.98 ± 0.09 g/l (about 54.58 ± 2.39%DCW) were received in only 12 h when grown in PPH. Interestingly, PHA productivity and biomass yield (Y_x/s) in PPH was about 4 times and 1.5 times higher than in glucose. To achieve the highest DCW and PHA production, the optimal culture conditions e.g. carbon to nitrogen ratios of 40 mole/mole, incubation temperature at 35℃ and shaking speed of 200 rpm were performed and a maximum DCW up to 4.24 ± 0.04 g/l and PHA concentration of 2.68 ± 0.02 g/l (61% DCW) were obtained. The produced PHA was further examined its monomer composition and found to contain only 3-hydroxybutyrate (3HB). This finding corresponded with the presence of class IV PHA synthase gene. Finally, certain thermal properties of the produced PHA i.e. the melting temperature (T_m) and the glass transition temperature (T_g) were about 176℃ and -4℃, respectively whereas the M_w was about 1.07 KDa ; therefore, the newly isolated B. megaterium PP-10 is a promising bacterial candidate for the efficient conversion of low-cost PPH to PHA.

• Journal of Microbiology and Biotechnology
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• v.34 no.6
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• pp.1229-1238
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• 2024

This study aimed to develop and assess a chitosan biomedical antibacterial gel ZincOxide-GrapheneOxide/Chitosan/β-Glycerophosphate (ZnO-GO/CS/β-GP) loaded with nano-zinc oxide (ZnO) and graphene oxide (GO), known for its potent antibacterial properties, biocompatibility, and sustained drug release. ZnO nanoparticles (ZnO-NPs) were modified and integrated with GO sheets to create 1% and 3% ZnO-GO/CS/β-GP thermo-sensitive hydrogels based on ZnO-GO to Chitosan (CS) mass ratio. Gelation time, pH, structural changes, and microscopic morphology were evaluated. The hydrogel's antibacterial efficacy against Porphyromonas gingivalis, biofilm biomass, and metabolic activity was examined alongside its impact (MC3T3-e1). The findings of this study revealed that both hydrogel formulations exhibited temperature sensitivity, maintaining a neutral pH. The ZnO-GO/CS/β-GP formulation effectively inhibited P. gingivalis bacterial activity and biofilm formation, with a 3% ZnO-GO/CS/β-GP antibacterial rate approaching 100%. MC3T3-e1 cells displayed good biocompatibility when cultured in the hydrogel extract.The ZnO-GO/CS/β-GP thermo-sensitive hydrogel demonstrates favorable physical and chemical properties, effectively preventing P. gingivalis biofilm formation. It exhibits promising biocompatibility, suggesting its potential as an adjuvant therapy for managing and preventing peri-implantitis, subject to further clinical investigations.

• Korean Journal of Breeding Science
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• v.43 no.6
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• pp.519-523
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• 2011

''Nokyang', a new high biomass yield and whole crop silage rice (Oriza sativa L.) cultivar, was developed by the rice breeding team of National Institute of Crop Science, RDA, Suwon, Korea, during the period from 1996 to 2006 and released in 2007. It was derived from a cross between Yongmoonbyeo/IR67396-16-3-3-1. This cultivar has about 130 days of growth duration from seeding to heading and is tolerance to lodging with erect pubescent leaves, semidwarf (culm length 78 cm) and thick culm. This cultivar has less tillers per hill and more spikelet numbers per panicle than Dasanbyeo. 'Nokyang' has wide and stay green leaf compared other Tongil-type varieties. This new variety is resistant to grain shattering and to some disease including bacterial leaf blight and stripe virus. This variety has good qualities for whole crop silage with high TDN (Total Digestive Nutrient) yield and low NDF (Neutral Detergent Fiber) and low ADF (Acid Detergent Fiber) and high RFV (Relative Feed Value) compared to common high grain yield varieties. The biomass and TDN yield performance of 'Nokyang' is 1,652 MT/ha, 9.9 MT/ha, individually in local adaptability test for three years. 'Nokyang' is adaptable to central plain area, south-eastern plain area of Korea.

• KSBB Journal
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• v.7 no.4
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• pp.296-301
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• 1992

A Pseudomonas fluorescens was selected from mushrooms and studied in both batch and fed-batch cultures in order to get maximal biomass concentration. P. fluorescens is an aerobic bacterium and antagonistic to Pseudomonas tolaasii which causes blotch disease on the mushroom cap. P fluarescens and P. tolaasii were identified by Gram staining, gelatin liquefaction, oxidase test, etc. and were characterized by pigment production, temperature sensitivity, salt tolerance and rapid pitting test, etc., Celts of P. fluorescens well in medium containing 30g/L of glucose, whereas the growth was inhibited at the glucose levels at higher than 30g/L. The highest values of specific growth rate and productivity were obtained when using 10g/1 of yeast extract. Optimum concentrations of $NH_4Cl$ and ${(NH_4Cl)}_2SO_4$ for culture were found to be 1.0g/L and 0.1g/L respectively. Optimum concentration of $MgSO_4{\cdot}7H_2O$ used as a sulfursource was 1.0g/L. It was also found that the cell concentrations reached the maximum level when grown on the medium containing 1.0g/L of $KH_2PO_4$ and 0.1g/L of $CaCl_2$. Also, the optimum culture conditions were $30^{\circ}C$ and pH 6.0. Cultivation of P. fluarescens at high dissolved oxygen (DO) concentration led to a decrease of bacterial productivity in batch culture. Maximum productivity was achieved at 40% DO concentration.