• Resources Recycling
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• v.29 no.1
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• pp.17-24
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• 2020

In this study, rare earth elements (REE) leaching from a refractory REE ore containing goethite as a major gangue mineral was conducted, introducing a two-stage method of chemical decomposition-acid leaching. At the chemical decomposition step, using one of alkaline agent, NaOH, the ore was decomposed, changing NaOH concentration from 20 to 50 wt% at 10% (w/w) of pulp density and the maximum temperature achieved without boiling at each NaOH concentration. With increasing NaOH concentration, light REE (Ce, La and Nd) and iron were concentrated in the solid phase which is the decomposed product, while aluminum (Al) and phosphorus (P) were removed to the liquid phase, and their concentrations in the solid phase were down to 0.96 and 0.17%, respectively. In addition, through XRD analysis, it was found that the crystallinity of goethite was considerably decreased. At the acid leaching step, the product decomposed by 50 wt% NaOH was leached at 3.0 M HCl and 80 ℃ for 3 hr, then the REE leaching efficiency was above 94% (Ce 80%), and the leaching efficiencies of Al and P were decreased to 12 and 0%, respectively. Therefore, in terms of both REE leaching efficiency and impurity removal, those decomposition and leaching conditions were chosen as optimum processing methods of the investigated material. In terms of REE leaching mechanism, because REE and iron leaching efficiencies showed the positive correlation each other, so it can be concluded that decreasing crystallinity of goethite affect the improvement of REE leaching.

• Journal of Mushroom
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• v.17 no.1
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• pp.24-33
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• 2019

The physicochemical characteristics of oyster mushrooms (Pleurotus ostreatus) cultivated using liquid spawn (MLS) were compared with those of commercial mushrooms cultivated using solid spawn. The color intensity of the two types of mushrooms showed no remarkable difference. The hardness of the MLS-cultivated mushrooms was significantly higher, but their moisture content (86.80%) was significantly lower than that of the commercial mushrooms. Mineral contents in MLS-cultivated mushrooms (421.17 mg/100 g) were significantly higher than those in the commercial mushrooms (333.26-362.78 mg/100 g); in particular, the potassium (K) content was the most abundant in the former. The amino acid content in the MLS-cultivated mushrooms (4,695.22 mg/100 g) was about 1.4-2.0 times that in the commercial mushrooms. The essential amino acid contents and sum of aspartic acid and glutamic acid were higher in the MLS-cultivated mushrooms than in the commercial mushrooms. The ${\beta}-glucan$ content in the MLS-cultivated mushrooms was 1.1-2.3 times higher than that in the commercial mushrooms. The total phenol and flavonoid contents and the DPPH and ABTS radical-scavenging activities of the MLS-cultivated mushrooms were significantly higher than those of the commercial mushrooms; however, the reducing power showed an opposite trend. Therefore, MLS-cultivated mushrooms contained higher amounts of valuable components and higher antioxidant activities than commercial mushrooms.

• Clean Technology
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• v.15 no.4
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• pp.273-279
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• 2009

$SF_6$, which has a high global warming potential, can be decomposed to sulfur and fluorine compounds through hydrolysis by $H_2O$ or oxidation by $O_2$ over solid acid catalysts. In this study ${\gamma}-Al_2O_3$ was employed as the solid acid catalyst for the abatement of $SF_6$ and its catalytic activity was investigated with respect to the reaction temperature and the space velocity. The catalytic activity for $SF_6$ decomposition by the hydrolysis reached the maximum at and above 973 K with the space velocity of $20,000\;ml/g_{-cat}{\cdot}h$, exhibiting a conversion very close to 100%. When the space velocity was lower than $45,000\;ml/g_{-cat}{\cdot}h$, the conversion was maintained at the maximum value. On the other hand, the conversion of $SF_6$ by the oxidation was about 20% under the same conditions. The SEM and XRD analyses revealed that the ${\gamma}-Al_2O_3$ was transformed to ${\alpha}-Al_2O_3$ during the hydrolysis and to $AlF_3$ during the oxidation, respectively. The size of $AlF_3$ after the oxidation was over $20\;{\mu}m$, and its catalytic activity was low due to the low surface area. Therefore, it was concluded that the hydrolysis over ${\gamma}-Al_2O_3$ was much more favorable than the oxidation for the catalytic decomposition of $SF_6$.

• Microbiology and Biotechnology Letters
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• v.39 no.4
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• pp.357-363
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• 2011

This study focus was primarily the development of liquid starters for Aspergillus oryzae and Aspergillus niger prepared with wheat bran as a low cost culture medium. For the preparation of the liquid media wheat bran was added at rates of 0, 5, 10, 15 and 20% and the Aspergillus sp. strains were then inoculated to these prepared broths. The results indicated that the more that wheat bran was contained in the medium, the more mycelia was produced for A. oryzae and A. niger. The highest enzyme activities were obtained with a 10~15% adding rate of wheat bran for both strains. Changes in the enzyme activities of the liquid starters during various incubation times (0, 24, 48, 72 and 96 hrs), indicated that the highest enzyme activities were seen between 48 and 72 hrs of culture. In addition, a comparative study was carried out on the production of enzymes using wheat as a substrate in nuruk, with liquid starter made from fermented agents according to the same concentrations used with the wheat bran. The pH, acidity, amino acidity, reducing sugar content and enzyme activity (${\alpha}$-amylase, glucoamylase, acidic protease) of wheat nuruk made with liquid starter were compared with those of wheat nuruk made with solid starter. The results suggest that the liquid starter is superior in both cases.

• Journal of the Korean Applied Science and Technology
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• v.32 no.1
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• pp.93-99
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• 2015

The aim of this study was to analyze nutritional compositions of rapeseed pollen granules and to determine the possible usage of pollen granules as a yeast culture medium. Rapeseed pollen granules (per 100 g) were consisted of carbohydrate 58.9 g, protein 20.8 g, fat 4.1 g, ash 2.5 g and water 13.7 g. And fructose (13.7 g), glucose (11.1 g), and sucrose (6.6 g) of sugars and K (606.7 mg) and P (603.3 mg) of minerals were highly contained. In addition, free amino acids such as glutamic acid (2,482.4 mg), aspartic acid (2,136.5 mg), lysine (1,648.3 mg), and leucine (1,631.1 mg) were present at a higher level. When liquid medium, which was made from cracked pollen granules (5, 10, 15, 20, 25, 30, and 40 g/L), was tested for yeast culture, liquid medium containing pollen granules over 15 g/L showed higher yeast growth than YPD medium (control). Liquid medium containing both cracked pollen granules (15 g/L) and NaCl (1 ~ 20 g/L) improved yeast growth than the liquid medium without NaCl. In addition, when yeast growth was tested on solid medium made from pollen granules (15 g/L) at $30^{\circ}C$ for 2 days, yeast colonies were equally well-formed like those grown on YPD medium. Overall, rapeseed pollen granules have potential properties on yeast growth and could be used as a primary source for yeast culture.

• Journal of Mushroom
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• v.20 no.2
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• pp.86-91
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• 2022

Pleurotus eryngii, a white rot fungus, produces two extracellular lignin-degrading enzymes, laccase and manganese peroxidase (MnP). Owing to these enzymes, P. eryngii efficiently degrades synthetic chemicals such as azo, phthalocyanine, and triphenyl methane dyes. In this study, we investigated the degradation processes of four aromatic dyes, congo red (CR), methylene blue (MB), crystal violet (CV), and malachite green (MG), by P. eryngii under solid and liquid culture conditions. CR and MG were the most quickly degraded under solid and liquid culture conditions, respectively. However, compared to CR, CV, and MG, MB was not degraded well under both culture conditions. The activities of ligninolytic enzymes (laccase and MnP) were also investigated. Laccase was identified to be the major enzyme for dye degradation. A positive relationship between decolorization and enzyme activity was observed for CR, MB, and CV degradation. In contrast, decolorization of MG ensued after high enzyme activity. These results indicate that the degradation process differs between MG and the other aromatic dyes. Therefore, P. eryngii could be a potential tool for the bioremediation of synthetic aromatic dye effluent.

• Food Science and Preservation
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• v.30 no.6
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• pp.1012-1028
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• 2023

The findings of this study confirmed the alteration of β-glucosidase activity, nutritional constituents, isoflavones, antioxidant activities, and digestive enzyme inhibition activities in soybeans during solid-state fermentation times with mycelia of Tricholoma matsutake. After nine days, the highest activity level was observed for β-glucosidase (3.90 to 38.89 unit/g) and aglycones (163.03 to 1,074.28 ㎍/g). The sum of isoflavones showed a significant decrease (3,489.41 to 1,325.66 ㎍/g) along with glycosides (2,753.87 to 212.43 ㎍/g) for fermentation, while fatty acids showed a slight increase and amino acids showed a marked increase. Total phenolic and flavonoid contents showed a corresponding increase according to fermentation times (5.58 to 15.09 GAE mg/g; 0.36 to 1.58 RE mg/g). Antioxidant and enzyme inhibition activities also increased; in particular, the highest level of scavenging activities was observed for ABTS (up 60.13 to 82.08%), followed by DPPH (up 63.92% to 71.98%) and hydroxyl (up 36.01 to 52.02%) radicals. Of particular interest, α-glucosidase (6.69 to 83.49%) and pancreatic lipase inhibition (1.22 to 77.43%) showed a marked increase. These results demonstrated that fermentation of soybeans with the mycelia of T. matsutake enhanced the nutritional and functional constituents, and the biological activities of soybeans. Thus, this fermentation technology can be used to produce a novel functional materials from soybeans.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.3 no.2
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• pp.105-112
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• 2005

The electrolytic reduction of uranium oxide in a LiCl-Li$_{2}$O molten salt system has been studied in a 10 g U$_{3}$O$_{8}$ /batch-scale experimental apparatus with an integrated cathode assembly at 650$^{\circ}C$. The integrated cathode assembly consists of an electric conductor, the uranium oxide to be reduced and the membrane for loading the uranium oxide. From the cyclic voltammograms for the LiCl-3 wt$\%$ Li$_{2}$O system and the U$_{3}$O$_{8}$-LiCl-3 wt$\%$ Li$_{2}$O system according to the materials of the membrane in the cathode assembly, the mechanisms of the predominant reduction reactions in the electrolytic reactor cell were to be understood; direct and indirect electrolytic reduction of uranium oxide. Direct and indirect electrolytic reductions have been performed with the integrated cathode assembly. Using the 325-mesh stainless steel screen the uranium oxide failed to be reduced to uranium metal by a direct and indirect electrolytic reduction because of a low current efficiency and with the porous magnesia membrane the uranium oxide was reduced successfully to uranium metal by an indirect electrolytic reduction because of a high current efficiency.

• Journal of the Mineralogical Society of Korea
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• v.5 no.2
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• pp.109-121
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• 1992

For the purpose of mineralogical and chemical study on the topazes from various localities of world(Brzail, China, India, Nigeria and Sri Lanka), electron microprobe analysis(EPMA), neutron activation analysis(NAA), X-ray diffractometry, Raman spectroscopy, etch test, scanning electron microscopy, refractive index, specific gravity, fluid inclusion were performed. The chemical composition in topaz was discussed along with its physical and structural properties. Variations in the unit-cell dimension and physical properties of topaz were found to have a close relations in the unit-cell dimension and physical properties of topaz were found to have a close relationship with extent of substitution of $OH^-\;for\;F^-$. According to neutron activation analyses, the trace elements had no effects on the physical properties of topaz. Raman spectra showed that the peaks of topaz were different in intensity from one locality to another. Etching defects in topaz includes negative crystal defect o point-bottom pit(India, Nigeria) and net work defect of curl-bottom pit(Brazil, China). Fluid inclusions in topaz may be classiffied into liquid $CO_2$-bearing inclusion, gaseous inclusion, halite, sylvite-bearing inclusion and liquid inclusion. The results of this study can be useful to devising artificial coloring methods for topaz with different mineralogical compositions.

• Journal of Mushroom
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• v.13 no.1
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• pp.63-67
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• 2015

White rot fungi produce lignin-degrading enzymes such as laccase, manganese peroxidase and lignin peroxidase. These extracellular oxidases efficiently degrade recalcitrant synthetic dyestuffs with diverse chemical structures. Here, we examined the activities of lignin-degrading enzymes in Trametes versicolor using triphenyl methane dyes, crystal violet (CV) and malachite green (MG). Both dyes were decolorized by T. versicolor in solid and liquid culture conditions. T. versicolor decolorized MG more quickly than CV in both conditions. Among three ligninolytic enzymes, laccase was most abundantly found in the decolorization processes of CV and MG. However, higher activity of laccase was needed to degrade CV than MG. The much less activity of MnP was also detected. But the increase of MnP activity was well corresponded to the decolorization efficiency of CV, suggesting the involvement of MnP in CV degrading process. However, its role in the degradation process of MG is supposed to be subsidiary to laccase.