• Journal of Microbiology and Biotechnology
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• v.34 no.2
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• pp.407-414
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• 2024

Phosphorus is an essential but non-renewable nutrient resource critical for agriculture. Luxury phosphorus uptake allows microalgae to synthesize polyphosphate and accumulate phosphorus, but, depending on the strain of algae, polyphosphate may be degraded within 4 hours of accumulation. We studied the recovery of phosphorus from wastewater through luxury uptake by an engineered strain of Synechocystis sp. with inhibited polyphosphate degradation and the effect of this engineered Synechocystis biomass on lettuce growth. First, a strain (∆phoU) lacking the phoU gene, which encodes a negative regulator of environmental phosphate concentrations, was generated to inhibit polyphosphate degradation in cells. Polyphosphate concentrations in the phoU knock-out strain were maintained for 24 h and then decreased slowly. In contrast, polyphosphate concentrations in the wild-type strain increased up to 4 h and then decreased rapidly. In addition, polyphosphate concentration in the phoU knockout strain cultured in semi-permeable membrane bioreactors with artificial wastewater medium was 2.5 times higher than that in the wild type and decreased to only 16% after 48 h. The biomass of lettuce treated with the phoU knockout strain (0.157 mg P/m²) was 38% higher than that of the lettuce treated with the control group. These results indicate that treating lettuce with this microalgal biomass can be beneficial to crop growth. These results suggest that the use of polyphosphate-accumulating microalgae as biofertilizers may alleviate the effects of a diminishing phosphorous supply. These findings can be used as a basis for additional genetic engineering to increase intracellular polyphosphate levels.

• Proceedings of the Microbiological Society of Korea Conference
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• 2004.05a
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• pp.101-104
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• 2004

Among biological hydrogen production processes, fermentative processes have some advantages. In this research, the hydrogen producing bacterium was isolated from domestic landfill area and identified as Enterobacter sp. The strain was named Enterobacter sp. SNU-1453. Important parameters for the hydrogen process include pH, temperature, concentration of initial glucose, and kind of sugars. The pH of the culture medium significantly decreased as fermentation proceeded due to the accumulation of various organic acids, and this inhibited the $H_2$ production seriously. When pH was controlled at pH 7.0, hydrogen production was 2614.5 m1/1 in 17 hours. The increase of glucose concentration resulted in higher $H_2$ production. The productivity of this strain was 6.87 mmol $H_2/l$ per hi on concentration of 25g glucose/l. Enterobacter sp. SNU-1453 could utilize various sugars. These results indicate that Enterobacter sp. SNU-1453 has a high potential as a fermentative $H_2$ producer.

• Microbiology and Biotechnology Letters
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• v.4 no.3
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• pp.111-115
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• 1976

A strain of Enterobacter cloacae isolated from soil showed the evidence of growth in medium containing 1,500 ppm of Cd$\^$＋＋/ though its growth was inhibited at high cadmium concentrations. This strain accumulated 59％ of cadmium into the cells during incubation in medium containing 0.5 ppm of cadmium and its uptake was nearly proportional to the dry weight of cells, the average being 7.8 mg cadmium per g dry cells. It was also found that 60-70％ of cadmium accumulated in cells were distributed in the cell wall fraction.

• Journal of Microbiology and Biotechnology
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• v.2 no.2
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• pp.129-134
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• 1992

Segregational instability of a recombinant plasmid, pDML6, encoding extracellular $\beta$-lactamase in Streptomyces lividans PD6 was characterized by growth kinetic analysis. The quantitative determination of the plasmid harbored in the mycelia was evaluated with mycelia fragmented mechanically, and also with colonies regenerated from protoplasts. Conditions for the formation of protoplasts and regeneration of protoplasts were established. The maximal specific growth rates of the host strain and the plasmid-harboring strain in a chemically defined medium without selection pressure were the same. The probability of plasmid loss from the harbouring cells was higher at higher growth rates. Mathematical models for the prediction of cell growth, substrate uptake, and accumulation of the cloned gene product were developed.

• Microbiology and Biotechnology Letters
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• v.21 no.2
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• pp.119-124
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• 1993

An alkalophilic microorganism for overproduction of cyclodextrin glucanotransferase (CGTase) was newly isolated from hot-water spring soil, and identified as Bacillus firmus var. alkalophilus H609. The strain maintained stability during preservation and cultivation for the enzyme production, and produced significant amount of CGTase corresponding to the volumetric activity of 75 units/mL at 37C, initial pH of 11.2, and after 40 hours. The strain excreted several different proteins showing CGTase activity that catalyzed the formation of mainly beta-and Gamma-type cyclodextrin (ratio of 7:1) from soluble starch without accumulation of alpha-type. Other enzymatic properties were also investigated.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2000.04a
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• pp.119-122
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• 2000

Dynamic deformation of metallic materials mostly accompanies substantial amounts of deformation heat. Since the flow stress of deformation is sensitive to temperature implication of heat due to plastic work is essential to the evaluation of constitutive relations. In this study a series of compression tests were conducted for SAF 2507 super duplex stainless steel and the accumulation of deformation heat was calculated through numerical integration method. Isothermal flow surfaces were deduced from subsequent logarithmic interpolation. Simple closed die forging process was analyzed and optimized with commercial FEM code applying both raw and calibrated material database.

• Journal of Microbiology and Biotechnology
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• v.9 no.6
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• pp.873-876
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• 1999

Aspergillus sp. CX-l strain grown on microcrystalline cellulose resulted in the accumulation of high levels of cellulase and xylanase activities that were higher by two to four folds than those from the conventional commercial producer, Trichoderma reesei QM9414. Aspergillus sp. CX-1 demonstrated greater thermo stability and better catalytic characteristics of total cellulase activity (FPase) as compared to T. reesei and Aspergillus niger F-2039.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.10a
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• pp.326-329
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• 2005

Since the required strength of forged part is achieved by work hardening with the accumulation of plastic strain during the cold working, severe load can be exerted on die system. So, dies are liable to the early fracture for the non-heat treated steel forging in comparison with the conventional mild steels. Therefore, it is necessary to lower the flow stress of steels as much as possible during forging steps. Bauschinger effect can be utilized to lower flow stress during forging steps by giving the tensile prestrain on the forging billet during wire drawing step. In the present study, the prestrain effect on Bauschinger phenomenon is studied to avoid difficulties with application of non-heat treated cold forging steels in practice.

• Structural Engineering and Mechanics
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• v.3 no.2
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• pp.185-192
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• 1995

A numerical algorithm for plane stress and shell elasto-plasticity is presented in this paper. The proposed strain decomposition (SD) algorithm is an elastic predictor/plastic corrector algorithm, and in the context of operator splitting, is a return mapping algorithm. However, it differs significantly from other return mapping algorithms in that only the necessary response functions are used without invoking their gradients, and the stress increment is updated only at the end of the time step. This makes the proposed SD algorithm more suitable for materials with complex yield surfaces and will guard against error accumulation during the time step. Comparative analyses of structural systems using the proposed strain decomposition (SD) algorithm and the iterative radial return (IRR) algorithm are presented. The results demonstrate the accuracy and usefulness of the proposed algorithm.

• Asian-Australasian Journal of Animal Sciences
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• v.14 no.3
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• pp.333-337
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• 2001

This study investigated the effects of fermented product from Bacillus subtilis (FPBS) on feed conversion efficiency, fat accumulation and ammonia production in broiler chicks. Sixty female broilers (strain Chunky, 7-day old) were divided into four groups and raised in individual cages. One group was fed a commercial diet without supplementation of FPBS as the control and the other three groups were fed commercial diets containing FPBS, either 0.5, 1.0 or 2.0%, for 21 days from 7 to 28 days of age. Water and feed were given ad libitum. Feed conversion efficiency was significantly improved in chicks supplemented with 0.5 or 1.0% of FPBS as compared with the control (p<0.05). The activities of hepatic acetyl-CoA carboxylase and fatty acid synthetase, and contents of triglyceride and cholesterol in the liver were significantly decreased in treatment groups (p<0.05) as compared with the control group. FPBS had no effect on the concentration of plasma triglyceride, phospholipids and cholesterol. Feeding FPBS at 1 % or 2% levels reduced ammonia gas release (p<0.05). The inclusion of FPBS at 1 % level may be recommended both to improve production efficiency and to reduce air pollution caused by ammonia gas release. For production efficiency to reach maximal profit, the inclusion of FPBS at 0.5% level can be recommended. Feeding FPBS reduced fat accumulation in the liver.