• Microbiology and Biotechnology Letters
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• v.11 no.3
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• pp.193-199
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• 1983

Systematic bioconversion process for the production of xylose from agricultural wastes such as barley straw and corn cobs was studied. After the pretreatment in 1 % NaOH solution for 24 hours at 3$0^{\circ}C$, enzymatic hydrolysis of barley straw for 48 hours at 3$0^{\circ}C$ resulted in the liberation of 15.8% of reducing sugar which is equivalent to 87% of total D-xylose content. Among various agricultural wastes, corn cob as well as barley straw was demonstrated to be potent sources for the production of D-xylose by the process of enzymatic conversion.

• Korean Journal of Medicinal Crop Science
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• v.21 no.5
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• pp.401-414
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• 2013

Ginsenoside Rg3 (G-Rg3) contained only in red ginseng has been found to show various pharmacological effects such as an anticancer, antiangiogenetic, antimetastastic, liver protective, neuroprotective immunomodulating, vasorelaxative, antidiabetic, insulin secretion promoting and antioxidant activities. It is well known that G-Rg3 could be divided into 20(R)-Rg3 and 20(S)-Rg3 according to the hydroxyl group attached to C-20 of aglycone, whose structural characteristics show different pharmacological activities. It has been reported that G-Rg3 is metabolized to G-Rh2 and protopanaxadiol by the conditions of the gastric acid or intestinal bacteria, thereby these metabolites could be absorbed, suggesting its absolute bioavailability (2.63%) to be very low. Therefore, we reviewed the chemical, physical and biological transformation methods for the production on a large scale of G-Rg3 with various pharmacological effects. We also examined the influence of acid and heat treatment-induced potentials on for the preparation method of higher G-Rg3 content in ginseng and ginseng products. Futhermore, the microbial and enzymatic bio-conversion technologies could be more efficient in terms of high selectivity, efficiency and productivity. The present review discusses the available technologies for G-Rg3 production on a large scale using chemical and biological transformation.

• Journal of the Korean Wood Science and Technology
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• v.40 no.3
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• pp.147-155
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• 2012

Switchgrass was selected as a promising biomass resource for bioethanol production through popping pretreatment, enzymatic saccharification and fermentation using commercial cellulase and xylanase, and fermenting yeast. The reducing sugar yields of popping pretreated switchgrass after enzymatic saccharification were above 95% and the glucose in thesaccharificaiton solution to ethanol conversion rate after fermentation with $Saccharomyces$ $cerevisiae$ was reached to 89.6%. Chemical compositions after popping pretreatment developed in our laboratory were 40.8% glucose and 20.3% xylose, with much of glucose remaining and only xylose decreased to 4.75%. This means that the hemicelluloses area broke off during popping pretreatment. FE-SEMexamination of substrate particles after popping pretreatment was showed fiber separation, and tearing and presence of numerous micro pores. These changes help explain, enhanced enzymatic penetration resulting in improved hydrolysis of switchgrass particles after popping pretreatment.

• Microbiology and Biotechnology Letters
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• v.20 no.1
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• pp.73-78
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• 1992

- Enzymatic synthesis of L-tryptophan(Trp) using E. coli tryptophanase has been investigated. In order to reduce the substrate inhibition by indole and to increase the product yield of L-tryptophan three different approaches have been made in this work. First, indole was intermittently fed to the reaction mixture in order to control the indole concentration at lower level. When 15 mM of indole was used as a total amount of substrate, conversion yield of 80% has been obtained with intermittent feeding while only 20% of indole was converted into L-tryptophan by conventional batch operation, The second method employed in this work was the use of cyclohexane-phosphate buffer organic two-phase system. In this system, indole was mainly partitioned into the organic-solvent phase and therefore substrate inhibition was expected to be reduced. L-Tryptophan production in organic two-phase system was, however, unexpectedly lower than that obtained in aqueous buffer solution. As a third method cyclodextrins have been added to the aqueous reaction mixture. It was found that the addition of $\beta$-cyclodextrin enhanced the tryptophan synthesis noticeably while $\alpha$-cycfodextrin showed little effect on tryptophan production.

• Korean Chemical Engineering Research
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• v.54 no.4
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• pp.448-452
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• 2016

This study is for the effective pretreatment and saccharification of lignocellulosic biomass for a transport fuel receiving attention. The waste water during the pretreatment of biomass is major factor for determining the price of biofuel. Therefore, we conducted high concentration of organosolv pretreatment for decline waste water and reusing the solvent. We confirmed effect of organosolv pretreatment by components analysis and enzymatic hydrolysis of pretreated biomass. The corn stover was used for and 99.5 wt% of ethanol as a organosolv pretreatment. The pretreatment condition was varied 130 to $190^{\circ}C$ during the designated reaction times and the effect of pretreatment was investigated by enzymatic hydrolysis. The highest glucose conversion was more than 68% the pretreatment condition of $190^{\circ}C$ for 70 min or more. The solid remaining was more than 70% and almost of cellulose and hemicellulose were survived.

• Journal of Microbiology and Biotechnology
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• v.31 no.3
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• pp.464-474
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• 2021

Bacterial cytochrome P450 (CYP) enzymes are responsible for the hydroxylation of diverse endogenous substances with a heme molecule used as a cofactor. This study characterized two CYP154C3 proteins from Streptomyces sp. W2061 (CYP154C3-1) and Streptomyces sp. KCCM40643 (CYP154C3-2). The enzymatic activity assays of both CYPs conducted using heterologous redox partners' putidaredoxin and putidaredoxin reductase showed substrate flexibility with different steroids and exhibited interesting product formation patterns. The enzymatic characterization revealed good activity over a pH range of 7.0 to 7.8 and the optimal temperature range for activity was 30 to 37℃. The major product was the C16-hydroxylated product and the kinetic profiles and patterns of the generated hydroxylated products differed between the two enzymes. Both enzymes showed a higher affinity toward progesterone, with CYP154C3-1 demonstrating slightly higher activity than CYP154C3-2 for most of the substrates. Oxidizing agents (diacetoxyiodo) benzene (PIDA) and hydrogen peroxide (H2O2) were also utilized to actively support the redox reactions, with optimum conversion achieved at concentrations of 3 mM and 65 mM, respectively. The oxidizing agents affected the product distribution, influencing the type and selectivity of the CYP-catalyzed reaction. Additionally, CYP154C3s also catalyzed the C-C bond cleavage of steroids. Therefore, CYP154C3s may be a good candidate for the production of modified steroids for various biological uses.

• Korean Journal of Food Science and Technology
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• v.44 no.4
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• pp.460-466
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• 2012

Through an analysis of T-2 and HT-2 toxins in corn and brown rice, the effect of enzymatic deacetylation of T-2 toxin on HT-2 toxin was investigated. Gas chromatography (GC) with electron capture detection and high-performance liquid chromatography (HPLC) with fluorescence detection were used for quantitative determination. T-2 toxin was converted into HT-2 (84-86%) within 15 min in the presence of crude protein extracts from corn and brown rice. The absence of T-2 conversion was observed for autoclaved samples, in which the enzymes were inactivated. When phosphate buffered saline, followed by methanol, was used as the extraction solvent, recoveries of T-2 toxin spiked at 50 and 200 ${\mu}g/kg$ were from 60 to 87%, whereas those of HT-2 in the autoclaved samples were 0%. In non-autoclaved samples, recoveries of HT-2 were 37-66%, whereas those of T-2 were negligible. However, the conversion of T-2 into HT-2 was not observed when samples were extracted by methanol/water.

• 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.

• Journal of Nutrition and Health
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• v.36 no.1
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• pp.32-39
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• 2003

Phytoestrogens, especially soy-derived isoflavones, are receiving great scrutiny as a food supplement for preventing hormone dependent disease such as postmenopausal osteoporosis. Their beneficial effects are derived from aglycone form of isoflavones, such as daidzein, genistein or glycitein. In contrast to the common usage of soybean, black bean (Rhynchosia Molubilis : Yak-kong) has been used as a supplement for preventing postmenopausal osteoporosis in oriental medicine. To investigate the effects of the saliva, artificial stomach fluid, and digestive enzymes on the conversion of glycosidic isoflavone to aglycone form, soybean and black bean were extracted with 70% methanol and freeze-dried. The recovery yield of methanol extracts of black bean was 14.1% which was higher than that of soybean, 13.5%. In terms of total isoflavones, we routinely obtained larger amount of isoflavones from black bean than those from soybean. By incubating methanol extracts of soybean and black bean with IN HCI for 180 min, the proportions of aglycones relative to the total isoflavone were significantly increased (32.4% and 52.4%, respectively). In vitro conversion, digestive enzymes ($\beta$-glucosidase and $\alpha$-glucosidase) may hydrolyze glycosidic bond of isoflavone more effectively than saliva or artificial stomach fluid did. It seems to say that the activity of $\beta$-glucosidase was higher than those of $\alpha$-glucosidase. The rate of conversion of glucoside form to aglycone form in black bean and soybean was low in physiological condition (pH) tested, although the enzymatic hydrolysis of glucoside was active. These results demonstrated that the composition of aglycone in food may be the important factors in terms of the bioavailability of isoflavones. (Korean J Nutrition 36(1): 32-39, 2003)

• The Korean Journal of Mycology
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• v.21 no.4
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• pp.285-292
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• 1993

For the enzymatic conversion of 5'-XMP to 5'-GMP, partially purified XMP aminase from Escherichia coli was coupled with the yeast, Saccharomycrs cerevisiae, capable of ATP regeneration through glycolytic pathway. In order to elevate the level of XMP aminase in E. coli, $guaB^{-}(IMP\;dehydrogenase-less)$ mutant were introduced, and the yeast used as ATP supplier was treated by some method to increase its membrane permeability. The optimum conditions for efficient conversion reaction by energy-coupled system were investigated. As the results, a CH 41, $guaB^-$ mutant of E. coli K-12, showed 2.75 fold increase in the level of XMP aminase, compared with its parent cell. And the lyophylized yeast was the most effective at the ATP supplier. The optimum temperature and pH of conversion reaction were $40{\circ]C$ and pH 7.4, and the highest conversion ratio was shown under the reaction condition of 100 mM glucose, 100 mM inorganic phosphate and 6 mM AMP. When 36 units/ml XMP aminase used under the above conditions, the amount of 60 mg/ml yeast was sufficient to be used. Under the optimum condition, 71% of 1.8 mM(65.6 mg/100 ml) 5'-XMP was converted to 5'-GMP within 8 hr.