• Journal of Microbiology and Biotechnology
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• v.13 no.4
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• pp.501-508
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• 2003

Artificial coupling of one enzyme with another can provide an efficient means for the production of industrially important chemicals. Xylose reductase has been recently discovered to be useful in the reductive production of xylitol. However, a limitation of its in vitro or in vivo use is the regeneration of the cofactor NAD(P)H in the enzyme activity. In the present study, an efficient process for the production of xylitol from D-xylose was established by coupling two enzymes. A NADH-dependent xylose reductase (XR) from Pichia stipitis catalyzed the reduction of xylose with a stoichiometric consumption of NADH, and the resulting cofactor $NAD^+$ was continuously re-reduced by formate dehydrogenase (FDH) for regeneration. Using simple kinetic analyses as tools for process optimization, suitable conditions for the performance and yield of the coupled reaction were established. The optimal reaction temperature and pH were determined to be about $30^{\circ}C$ and 7.0, respectively. Formate, as a substrate of FDH, affected the yield and cofactor regeneration, and was, therefore, adjusted to a concentration of 20 mM. When the total activity of FDH was about 1.8-fold higher than that of XR, the performance was better than that by any other activity ratios. As expected, there were no distinct differences in the conversion yields of reactions, when supplied with the oxidized form $NAD^+$ instead of the reduced form NADH, as a starting cofactor for regeneration. Under these conditions, a complete conversion (>99%) could be readily obtained from a small-scale batch reaction.

• Applied Chemistry for Engineering
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• v.35 no.2
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• pp.134-139
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• 2024

In the steam reforming of methane reactions, the effect of adding noble metals Ru and Pd to a Ni-based catalyst as promoters was analyzed in terms of catalytic activity and hydrogen production. The synthesized catalysts were coated on the surface of a honeycomb-structured metal monolith to perform steam methane reforming reactions. The catalysts were characterized by XRD, TPR, and SEM, and after the reforming reaction, the gas composition was analyzed by GC to measure methane conversion, hydrogen yield, and CO selectivity. The addition of 0.5 wt% Ru improved the reduction properties of the Ni catalyst and exhibited enhanced catalytic activity with a methane conversion of 99.91%. In addition, reaction characteristics were analyzed according to various process conditions. Methane conversion of over 90% and hydrogen yield of more than 3.3 were achieved at a reaction temperature of 800 ℃, a gas hourly space velocity (GHSV) of less than 10000 h^-1, and a ratio of H₂O to CH₄ (S/C) higher than 3.

• Journal of the Korean Wood Science and Technology
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• v.38 no.3
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• pp.262-273
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• 2010

In the enzymatic hydrolysis of rice straw and wood meals using extra-cellular enzymes from Fomitopsis palustris, key factors which enhanced the sugar conversion yield were investigated in this work, such as enzyme production and enzyme reaction conditions, surfactant effects, and the surface structure of substrates. F. palustris cultured with softwood mixture produced 12.0 U/$m{\ell}$ for endo-${\beta}$-1,4-gulcanase (EG), 116.68 U/$m{\ell}$ for ${\beta}$-glucosidase (BGL), 18.82 U/$m{\ell}$ for cellobiohydrolase (CBH), and 13.33 U/$m{\ell}$ for ${\beta}$-xylosidase (BXL). These levels of BGL, CBH, and BXL activities were two to four folds more than enzyme activities of F. palustris cultured with rice straw. The optimum reaction conditions of cellulase-RS which produced by F. palustris with rice straw and cellulase-SW which produced by F. palustris with softwood mixture were pH 5.0 at $45^{\circ}C$ and pH 5.0 at $50^{\circ}C$, respectively. The sugar conversion yield of cellulase-SW had the highest value of $40.6{\pm}0.6%$ within 72 h when rice straw was used as substrate. By adding 0.1% Tween 20 (w/w-substrate), the sugar conversion yield of rice straw was increased to 44%, which was about four fifths sugar conversion yield of commercial enzyme, Celluclast 1.5L (Novozyme A/S). A low crystallinity and an intensive fibril surface observed by the scanning electron microscope may explain the high sugar conversion yield of rice straw.

• Korean Chemical Engineering Research
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• v.54 no.4
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• pp.519-526
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• 2016

Biomass derived jet fuel is proven as a potential alternative for the currently used fossil oriented energy. The efficient production of jet fuel precursor with special molecular structure is prerequisite in producing biomass derived jet fuel. We synthesized a new jet fuel precursor containing branched $C_{15}$ framework by aldol condensation of furfural (FA) and ethyl levulinate (EL), where the latter of two could be easily produced from lignocellulose by acid catalyzed processes. The highest yield of 56% for target jet fuel precursor could be obtained at the optimal reaction condition (molar ratio of FA/EL of 2, 323 K, 50 min) by using KOH as catalyst. The chemical structure of $C_{15}$ precursor was specified as (3E, 5E)-6-(furan-2-yl)-3-(furan-2-ylmethylene)-4-oxohex-5-enoic acid ($F_2E$). For stabilization, this yellowish solid precursor was hydrogenated at low temperature to obtain C=C bonds saturated product, and the chemical structure was proposed as 4-oxo-6-(tetrahydrofuran-2-yl)-3-(tetrahydrofuran-2-yl)-methyl hexanoic acid ($H-F_2E$). The successful synthesis of the new jet fuel precursors showed the significance that branched jet fuel could be potentially produced from biomass derived FA and EL via fewer steps.

• Journal of Energy Engineering
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• v.5 no.2
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• pp.176-182
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• 1996

The effects of some additives (black liquor, NaOH, water and wood) on the conversion of coal and product were investigated in the lab-scale, high pressure reacting system around 375$^{\circ}C$. The addition of black liquor enhances the coal conversion yield about 38.6%, which is mainly due to NaOH in black liquor. Also, sulfur of the black liquor in coal liquefaction process evolved hydrogen sulfide, which causes the odor problem. Addition of water in coal liquefaction increased CO$_2$content in the gas phase, and low boiling range components in liquid products. Coprocessing of wood and coal at 400$^{\circ}C$ increased yield of liquid product about 8%, but higher temperature above 400$^{\circ}C$ reduced liquid product due to increase of gas products.

• Microbiology and Biotechnology Letters
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• v.20 no.1
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• pp.61-67
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• 1992

The synthesis of N-benzyloxycarbonyl-L-aspartyl-L-phenylalanine methyl ester(ZAPM), a precursor of aspartame, from N-benzyloxycarbonyl-L-aspartic acid(Z-Asp) and L-phenylalanine methyl ester hydrochloride(L-PM-HCl) was investigated in ethylacetate-MES buffer two-phase system using thermolysin. In organic two-phase system, the degree of spontaneous hydrolysis of L-PM. HCl was significantly reduced with increasing the volume ratio of organic to aqueous phase. Stability of thermolysin in organic two-phase system was found to be higher than that in MES buffer solution. More than 90% of initial enzyme activity was maintained after 10 days of incubation in case that the volume of organic phase was equal to that of buffer phase, while the half life of thermolysin was about 2 days in aqueous buffer solution. The results of partitioning of substrates and product in organic two-phase system showed that the difference in partition coefficients between substrates and product was maximum at pH 5.5. The optimal pH for 2-APM synthesis in organic two-phase system was found to be 5.5-5.8, which is consistent with the value expected from the partition experiments. As the concentration of substrates was increased the conversion yield of Z-APM was increased with concomitant reduction of L-PMqHC1 hydrolysis. In case that the concentration of L-PM-HCl and Z-Asp were 160 mM and 80 mM respectively, the conversion yield of Z-APM reached 90% after 28 hrs of reaction. The yield obtained at different volume ratio of organic phase compares well with the predicted equilibrium constant in biphasic system.

• Asian-Australasian Journal of Animal Sciences
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• v.19 no.2
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• pp.198-202
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• 2006

An experiment was conducted to investigate the effect of phytase, organic acids and their interaction on body weight gain, feed consumption, feed conversion ratio, carcass yield and tibia ash. A total of 680 three-day old Japanese quail chicks (Coturnix coturnix japonica) were assigned to 20 battery brooders, 34 chicks in each. The experimental period lasted 35 days. The treatment groups employed were: 1) a positive control which included 3.5 g available phosphorus (AP)/kg diet and 10 g Ca/kg diet; 2) a negative control which included 2 g AP/kg diet and 8 g Ca/kg diet, 3) negative control diet supplemented with either 300 FTU phytase/kg diet (phytase) or 4) 2.5 g organic acid (lactic acid+formic acid)/kg diet (organic acid); or 5) 300 FTU phytase/kg diet+2.5 g organic acid/kg diet (phytase+organic acid). All birds were fed with the positive control diet for a week and then transferred to the dietary treatments. At the end of the study, there were no differences (p>0.005) among the groups in body weight, weight gain, feed consumption, feed conversion ratio and carcass yield. Tibia ash, however, was reduced (p<0.001) for quails fed the negative control diet containing a low-level of AP compared to the positive control diet containing adequate AP. The addition of phytase, organic acid or phytase+organic acid to the diets containing the low-level of AP improved (p<0.001) tibia ash. On the other hand, an extra synergistic effect of phytase and organic acid on tibia ash was not determined. This study demonstrated that it may be possible to reduce supplemental level of inorganic P with phytase and/or organic acid supplementation for quail diets without adverse effect on performance and tibia ash.

• Applied Chemistry for Engineering
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• v.10 no.8
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• pp.1200-1209
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• 1999

Prediction model was composed by optimal parameter estimation from best fitting on reactant temperature profile, inlet and outlet temperature of coolant and yield of dual fixed-bed catalytic reactor(FBCR) which was measured in the industrial field. In order to design the FBCR which could obtain maximum conversion and yield, we investigated the effect of catalyst bed length and reactor radius changes. An uniform activity FBCR showed the best performance at z = 2.8 m of total catalysst bed length in case of reactor radius r = 0.01241 m and z =2.80 m(upper layer: 1.88 m, lower layer: 0.92 m) under reactor radius r = 0.01254 m for a dual activities FCBR. In case of reactor radius changes, the axial temperature profile and maximum radial temperature was rapidly risen for radius increase. The reactor radius decrease showed the opposite result.

• Journal of the Korean Applied Science and Technology
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• v.39 no.1
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• pp.1-9
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• 2022

1, 2-Octanediol (OD) as a cosmetic additive has been used simultaneously as a preservative and humectant. To solve the skin problem by 1, 2-octanediol (OD), we have synthesized 1, 2-octanediol galactoside (OD-gal) using Escherichia coli β-galactosidase (β-gal). Meanwhile, the optimal amount of β-gal, OD concentration, pH, and temperature for OD-gal synthesis were 4.5 U/ml, 150 mM, 7.0, and 37℃, respectively. Under these conditions, 150 mM OD was converted into about 55.9 mM OD-gal during 24 hours, in which the conversion yield (mole basis) was about 37.2%. In addition, OD-gal of 67.4 mg could be purified from a 9 ml reaction mixture, in which the overall synthesis yield from OD to the purified OD-gal was about 34.1% (weight basis) and 16.2% (mole basis), respectively. We are expecting that these results will be helpful to develop a safer additive in the cosmetic industry as basic data.

• Journal of Microbiology and Biotechnology
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• v.11 no.4
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• pp.564-569
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• 2001

This study was carried out in order to investigate the characteristics of xylitol fermentation by a xylitol dehydrogenase defective mutant PXM-4 of P stipitis CBS 5776 and to determime optimum conditions for the high yield ofxylitol production from xylose. Gluconic acid was selected as a co substrate for the xylitol fermentation, since gluconic acid neither blocked xylose transport nor repressed xylose reductase expression. An increase of gluconic acid concentration reduced the rates of xylitol production and cell growth by decreasing medium pH, and the optimal concentration of gluconic acid was determined to be 20 gll with approximately 100% xylitol conversion yield. A fed-batch cell culture resulted in a 44.8 g/l xylitol concentration with 100% yield, based on the amount of xylose consumed.