• Current Research on Agriculture and Life Sciences
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• 제11권
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• pp.81-89
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• 1993

xylA 유전자의 발현에 관한 xylR 유전자의 조절 메카니즘을 밝히기 위한 연구의 일환으로 xylA 프로모터 하류에 cat 유전자를 삽입시켜 Pxyl-cat-xylA 융합 플라스미드인 pEXC131을 제작하였고 이 플라스미드를 xylA 변이주인DH77로 형질전환시킨 결과 xylose의 유도시에만 Cm 내성과 xylose isomerase활성이 나타났다. pEXC1131/DH77에 NTG를 처리하여 xylose 유도없이도 Cm 내성과 xylose isomerase의 활성을 나타내는 xylA 유전자의 구성적 변이주인 pEXC131-39를 xylR 변이주인 DH60으로 형질전환시킨 균주가 xylose에 의한 유도와 무관하게 Cm 내성 및 xylose isomerase 활성을 가지는 것으로 보아 xylA 유전자의 프로모터부위의 변이에 의한 구성적 변이주임을 확인하였다.

• Journal of Microbiology and Biotechnology
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• 제20권5호
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• pp.946-949
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• 2010

The effects of two different sugars (glucose and xylose) on the expression levels and patterns of the xylose reductase (xyl1), xylitol dehydrogenase (xyl2), and xylulokinase (xyl3) genes were analyzed using Pichia stipitis. A significant increase in mRNA levels of xyl1 was observed after 6 h growth in culture conditions using xylose as a sole carbon source, but expressions of the three genes were not influenced by normal culture media with glucose. In addition, expressions of xyl2 and xyl3 were not observed during the entire culture period during which xylose was added. It also was found that the expression level of xyl1 increased as a function of the xylose concentration (40, 60, and 80 g/l) used in this study, indicating that xyl1 expression sensitively responded to xylose in the culture media. Although the induced level of xyl2 increased slightly after 48 h in the xylose-supplemented culture conditions, the expression of xyl2 was not observed in the xylitol-supplemented culture conditions. Finally, considering the expression of each gene in response to glucose or xylose, the absolute expression levels of the three genes indicate that xyl1 is induced primarily by exposure to xylose.

• 한국식품과학회지
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• 제28권5호
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• pp.970-973
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• 1996

Candida parapsilosis KFCC-10875를 사용하여 균체농도가 xylose로부터 xylitol의 생산에 미치는 영향을 조사하였다. Xylitol 생산속도는 균체농도 20 g/l에서 최대값 2.8 g/l-h를 보여주었으며 비 xylitol 생산속도는 농축된 균제에 의한 산소제한으로 균체농도가 증가할수록 감소하였다. 약 20 g/l로 농축된 균체를 사용하여 초기 xylose농도가 xylitol 생산에 미치는 영향을 살펴본 결과 xylitol 생산속도, 비 xylitol 생산속도 및 xylose에 대한 xylitol의 수율은 xylose의 농도 170 g/l에서 최대값을 보여주었다. 고농도의 균체를 사용하려면 xylose의 배지에서 배양된 균체를 다시 농축하여야 한다. 이러한 단점을 해결하기 위하여 발효과정 중에 균체를 농축하는 방법을 시도하였다. 고농도 균체를 얻기위하여 지수증식기인 배양 초기에는 용존산소의 농노를 충분히 유지시켜 18시간 배양하여 약 20 g/l의 고농도 균체를 얻을 수 있었다. 고농도 균체를 이용하여 xylitol을 생산하기 위하여 용존산소의 농도를 0.7-1.5%로 낮추어 유지하였다. 이때, 기질의 농도는 xylose 농도가 170 g/l 이상에서는 xylitol 생산성이 비교적 크게 감소하므로 xylitol 생산성의 향상을 위하여 고농도의 xylose를 피하는 유가식 배양을 수행하였다. 그 결과 56시간 배양하여 200 g/l xylose로부터 약 140 g/l의 xylitol을 생산할 수 있었다.

• 한국식품과학회지
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• 제29권5호
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• pp.1045-1051
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• 1997

Model melanoidin으로서 glucose-glycine, glucose-lysine, xylose-arginine melanoidin을 색도가 동일하게 되도록 조제하여 항산화효과 및 항산화효과와 관련된 특성을 살펴보았다. 실험에 사용한 melanoidin들은 대조군에 비해 강력한 항산화 효과를 나타내었으며 melanoidin들의 갈색도의 정도를 동일하게 하여도 당과 아미노산의 종류에 따라 항산화 효과가 다르게 나타나서 xylose-arginine melanoidin의 항산화 효과가 가장 큰 것으로 나타났다. Xylose-arginine melanoidin의 경우 DPPH에 의한 전자공여성도 실험에 사용한 세 model melanoidin중 가장 커서 xylose-arginine melanoidin의 항산화성과 전자공여성이 관계있음을 알 수 있었다. Melanoidin의 항산화 효과 관련 물질의 특성을 알기위하여 melanoidin을 Sephadex G-50에서 분리하여 그 특성을 조사한 결과 melanoidin의 종류에 따라 다른 분리 패턴을 나타내었다. 분획별 항산화효과를 비교한 결과 xylose-arginine melanoidin이 가장 강한 항산화효과를 나타내었고 다음이 glucose-lysine melanoidin이었으며 glucose-glycine melanoidin이 가장 낮은 항산화효과를 나타내어 당의 경우 glucose보다 xylose에서, 아미노산의 경우 glysine보다 lysine에서 항산화 효과가 큰 것을 알 수 있었다. 분획물의 특성 중 melanoidin의 항산화 효과가 큰 물질은 갈색도가 높으면서 ninhydrin 양성반응을 나타내고 환원성이 강한 특성을 나타내었다. Xylose-arginine melanoidin의 경우 fraction 50에서 65사이의 광범위한 영역에서, glucose-lysine melanoidin의 경우 fraction 65에서, glucose-glycine melanoidin의 경우 fraction 60에서 각각 강한 항산화 효과물질이 검출되었다. Xylose-arginine melanoidin의 경우 광범위한 갈색물질의 용출범위에서 환원작용을 나타내어 앞에서 model melanoidin 중 가장 강한 항산화 효과 및 DPPH에 의한 전자공여성을 나타낸 성질과 일치함을 알 수 있었다.

• Nutrition Research and Practice
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• 제10권1호
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• pp.11-18
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• 2016

BACKGROUND/OBJECTIVES: Type 2 diabetes (T2D) is more frequently diagnosed and is characterized by hyperglycemia and insulin resistance. $\small{D}$-xylose, a sucrase inhibitor, may be useful as a functional sugar complement to inhibit increases in blood glucose levels. The objective of this study was to investigate the anti-diabetic effects of $\small{D}$-xylose both in vitro and stretpozotocin (STZ)-nicotinamide (NA)-induced models in vivo. MATERIALS/METHODS: Wistar rats were divided into the following groups: (i) normal control; (ii) diabetic control; (iii) diabetic rats supplemented with a diet where 5% of the total sucrose content in the diet was replaced with $\small{D}$-xylose; and (iv) diabetic rats supplemented with a diet where 10% of the total sucrose content in the diet was replaced with $\small{D}$-xylose. These groups were maintained for two weeks. The effects of $\small{D}$-xylose on blood glucose levels were examined using oral glucose tolerance test, insulin secretion assays, histology of liver and pancreas tissues, and analysis of phosphoenolpyruvate carboxylase (PEPCK) expression in liver tissues of a STZ-NA-induced experimental rat model. Levels of glucose uptake and insulin secretion by differentiated C2C12 muscle cells and INS-1 pancreatic ${\beta}$-cells were analyzed. RESULTS: In vivo, $\small{D}$-xylose supplementation significantly reduced fasting serum glucose levels (P < 0.05), it slightly reduced the area under the glucose curve, and increased insulin levels compared to the diabetic controls. $\small{D}$-xylose supplementation enhanced the regeneration of pancreas tissue and improved the arrangement of hepatocytes compared to the diabetic controls. Lower levels of PEPCK were detected in the liver tissues of $\small{D}$-xylose-supplemented rats (P < 0.05). In vitro, both 2-NBDG uptake by C2C12 cells and insulin secretion by INS-1 cells were increased with $\small{D}$-xylose supplementation in a dose-dependent manner compared to treatment with glucose alone. CONCLUSIONS: In this study, $\small{D}$-xylose exerted anti-diabetic effects in vivo by regulating blood glucose levels via regeneration of damaged pancreas and liver tissues and regulation of PEPCK, a key rate-limiting enzyme in the process of gluconeogenesis. In vitro, $\small{D}$-xylose induced the uptake of glucose by muscle cells and the secretion of insulin cells by ${\beta}$-cells. These mechanistic insights will facilitate the development of highly effective strategy for T2D.

• KSBB Journal
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• 제13권1호
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• pp.6-12
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• 1998

In order to produce xylitol from hemicellulose hydrolysate which is widely used as a substrate, the development of strain such as catabolite derepressed mutant is required. After treatment of Candida sp. with EMS, GM-17 and PM-34 as catabolite derepressed mutant were isolated from Candida guilliermondii and Candida parapsilosis, respectively. Mutant GM-17 and PM-34 simultaneously assimilated xylose and glucose during the fermentation. The specific xylose reductase and xylitol dehydrogenase activities of mutant strains were also higher than those of wild strains in glucose medium and mixed medium of glucose and xylose. The xylitol productivity and yield of mutant GM-17 and PM-34 were improved as compared to the wild types in the mixed medium. The xylitol productivity and yield of mutant GM-17 were 0.09 g/L·hr and 0.56 g-xylitol/g-xylose, and those of mutant PM-34 were 0.21 g/L·hr and 0.52 g-xylitol/g-xylose in the mixed medium, respectively.

• 한국식품조리과학회지
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• 제11권4호
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• pp.396-400
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• 1995

The antioxidant effects in soybean oil was investigated by browning reaction mixtures formed by sugar and reaction temperatures above 110$^{\circ}C$. 0.1 M solution of xylose, glucose and sucrose were heated at 110, 120, 130, 140 and 150$^{\circ}C$ for 24 hrs respectively. A reaction rate constant(k), activation energy (Ea) and Q$\sub$10/ value were determined by color intensity that was measured absorbance at 490 nm in each temperature. Soybean oil containing the ethanol extracts taken from the browning reaction mixtures that were heated at 110, 130 and 150$^{\circ}C$ was stored in an incubator kept at 45.0${\pm}$1.0$^{\circ}C$ for 24 days. The results are as follows: 1. When 0.1 M solution of xylose, glucose and sucrose were heated at 110$^{\circ}C$ and 120$^{\circ}C$, the intensity of glucose browning mixtures was the highest, but heated at 150$^{\circ}C$, the color intensity increased in order of xylose > glucose > sucrose after 24 hrs. 2. The reaction rate constant (k) was increased rapidly above 140$^{\circ}C$ and appeared maximum at 150$^{\circ}C$, esp. xylose was the highest. The activation onergy (Ea) of xylose was the highest as 93.28 Joule/mole and the Q$\sub$10/ value of xylose was appeared 1.28. Q$\sub$10/ value was also the highest in xylose. 3. The browning reaction mixtures that were heated at 110$^{\circ}C$ appeared little antioxidant effects. But, in heated at 130$^{\circ}C$ and 150$^{\circ}C$, the antioxidant effects appeared in sucrose browning reaction mixtures. Therefore, in browning reaction mixtures that heated above 110$^{\circ}C$, only sucrose browning reaction mixtures appeared antioxidant effects and xylose, glucose appeared little antioxidant effects. On the contrary xylose and glucose increased peroxide values of soybean oil.

• 한국미생물·생명공학회지
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• 제47권4호
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• pp.565-573
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• 2019

섬유소계 바이오매스로부터 바이오 연료 등과 같은 유용한 물질을 생산하기 위해서는 바이오매스로부터 유래하는 혼합당을 효과적으로 대사할 수 있는 균주의 개발이 필수적이다. 본 연구에서는 xylose를 대사가 가능한 효모인 P. stipitis를 적응진화하여 cellobiose 대사효율이 향상되고 cellobiose와 xylose를 동시에 대사할 수 있는 균주를 개발하고자 하였다. 총 10회의 계대배양을 통해 얻어진 진화된 P. stipitis 돌연변이 균주는 모균주에 비해 6배 이상 증가된 cellobiose 대사속도를 나타내었으며 ethanol 생산수율을 0에서 0.4 (g ethanol/g cellobiose)로 향상시켰다. 아울러 본 실험에서 개발한 돌연변이 균주는 cellobiose와 xylose 혼합당 조건에서 모균주에 비해 2배 가까이 향상된 ethanol 생산 및 생산속도를 나타내었다.

• Journal of Microbiology and Biotechnology
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• 제19권1호
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• pp.65-71
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• 2009

Microbial oxidoreductive systems have been widely used in asymmetric syntheses of optically active alcohols. However, when reused in multi-batch reaction, the catalytic efficiency and sustainability of non-growing cells usually decreased because of continuous consumption of required cofactors during the reaction process. A novel method for NADPH regeneration in cells was proposed by using pentose metabolism in microorganisms. Addition of D-xylose, L-arabinose, or D-ribose to the reaction significantly improved the conversion efficiency of deracemization of racemic 1-phenyl-1,2-ethanediol to (S)-isomer by Candida parapsilosis cells already used once, which afforded the product with high optical purity over 97%e.e. in high yield over 85% under an increased substrate concentration of 15 g/l. Compared with reactions without xylose, xylose added to multi-batch reactions had no influence on the activity of the enzyme catalyzing the key step in deracemization, but performed a promoting effect on the recovery of the metabolic activity of the non-growing cells with its consumption in each batch. The detection of activities of xylose reductase and xylitol dehydrogenase from cell-free extract of C. parapsilosis made xylose metabolism feasible in cells, and the depression of the pentose phosphate pathway inhibitor to this reaction further indicated that xylose facilitated the NADPH-required deracemization through the pentose phosphate pathway in C. parapsilosis. moreover, by investigating the cofactor pool, the xylose addition in reaction batches giving more NADPH, compared with those without xylose, suggested that the higher catalytic efficiency and sustainability of C. parapsilosis non-growing cells had resulted from xylose metabolism recycling NADPH for the deracemization.

• 청정기술
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• 제22권4호
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• pp.250-257
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• 2016

As an attempt to replacing petroleum-based chemicals with bio-based ones, synthesis of furfural from biomass-derived xylose attracts much attention in recent days. Conventionally, furfural from xylose has been produced via the utilization of highly corrosive, toxic, and environmentally unfriendly mineral acids such as sulfuric acid or hydrochloric acid. In this study, microwave-assisted biphasic reaction process in the presence of novel bio-based heterogeneous acid catalysts was developed for the eco-benign and effective synthesis of furfural from xylose. The microwave was irradiated for reaction acceleration and a biphasic system consisting of $H_2O$ : MIBK (1 : 2) was designed for continuous extraction of furfural into the organic phase in order to reduce the undesired side products formed by decomposition/condensation/oligomerization in the acidic aqueous phase. Moreover, sulfonated amorphous carbonaceous materials were prepared from wood powder, the most abundant lignocellulosic biomass. The prepared catalysts were characterized by FT-IR, XPS, BET, elemental analysis and they were used as bio-based heterogeneous acid catalysts for the dehydration of xylose into furfural more effectively. For further optimization, the effect of temperature, reaction time, water/organic solvent ratio, and substrate/catalyst ratio on the xylose conversion and furfural yield were investigated and 100% conversion of xylose and 74% yield of furfural was achieved within 5 h at $180^{\circ}C$. The bio-based heterogeneous acid catalysts could be used three times without any significant loss of activity. This greener protocol provides highly selective conversion of xylose to furfural as well as facile isolation of product and bio-based heterogeneous acid catalysts can alternate the environmentally-burdened mineral acids.