• Nano
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• 제13권11호
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• pp.1850132.1-1850132.14
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• 2018

The direct synthesis of metal-organic frameworks (MOFs) with acidic and basic active sites is challenging due to the introduction of functional groups by post-functionalization method often jeopardize the framework integrity. Herein, we report the direct synthesis of acid-base bifunctional MOFs with tuning acid-base strength. Employing modulated hydrothermal (MHT) approach, microporous MOFs named $UiO-66-NH_2$ was prepared. Through the ring-opening reaction of 1,3-propanesultone with amino group, $UiO-66-NH_2-SO_3H-type$ catalysts can be obtained. The synthesized catalysts were well characterized and their catalytic performances were evaluated in one-pot glucose to 5-HMF conversion. Results revealed the acid-base bi-functional catalyst possessed high activity and excellent stability. This work provides a general and economically viable approach for the large-scale synthesis of acid-base bi-functional MOFs for their potential use in catalysis field.

• 한국식품과학회지
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• 제17권3호
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• pp.155-162
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• 1985

양봉밀과 토종봉밀의 일반성분, 당, 유리아미노산 조성, 저장중의 diastase활성도 및 HMF 변화는 다음과 같다. 일반 성분 중 조회분은 밤꿀이 0.46%로 다른 벌꿀에 비하여 많았고, 조단백질은 양봉밀이 평균 0.10%로서 토종봉밀에 비하여 약 3.2배가 많았다. 무기물은 밤꿀에 있어서 Ca이 2.07mg%, P이 6.81mg%, Fe이 2.70mg%로 가장 많았다. 저장 중 diastase활성도 변화에 있어서 $4^{\circ}C$ 또는 $20^{\circ}C$저장 온도에서의 단기간 저장으로는 그의 활성도가 거의 감소되지 않았으며, $70^{\circ}C$에서 30분간 가열처리로 효소의 활성도가 감소되었으나 이를 $20^{\circ}C$에 저장 하였을 때는 그렇지 않은 것과 거의 동일 하였다. 양봉밀의 평균 당조성은 fructose 40.20%, glucose 32.43%, sucrose 1.09%, fructose/glucose 비는 1.24였다. 또한 토종봉밀은 fructose 37.37%, gluctse 31.92%, sucrose 0.74%였으며 fructose/glucose비는 1.19였다. 유리아미노산의 조성은 총 16종을 확인하였는데 그 중 proline함량이 가장 많아 그 함량은 총 유리아미노산의 39.59-46.86%를 차지하는 14.02-14.40mg%였다. 그러고 밤꿀에서 Phe 이 3.28mg%로 9.26%를 차지하였으며 광양산의 토종봉밀에서 Asp가 2.76mg%로 8.98%를 차지하였다. 저장 중 HMF 함량변화는 $4^{\circ}C$ 저장에 서는 거의 없었으나, $20^{\circ}C$, 80일간의 저장에서 밤꿀이 0.470mg%, 아카시아꿀이 0.336mg%, 유채꿀이 0.164mg%, 토종봉밀인 광양산이 0.426mg%, 광주산이 0.259mg%, 운봉산이 0.117mg%로 증가되었다. 또한 $50^{\circ}C$에서 3주간 저장으로 유채꿀이 8.71mg%, 아카시아꿀이 7.79mg%, 밤꿀이 5.35mg%증가되었다.

• Journal of Microbiology and Biotechnology
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• 제30권12호
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• pp.1912-1918
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• 2020

Hyper-thermal (HT) acid hydrolysis of red seaweed Gelidium amansii was performed using 12% (w/v) slurry and an acid mix concentration of 180 mM at 150℃ for 10 min. Enzymatic saccharification when using a combination of Celluclast 1.5 L and CTec2 at a dose of 16 U/ml led to the production of 12.0 g/l of reducing sugar with an efficiency of enzymatic saccharification of 13.2%. After the enzymatic saccharification, 2,3-butanediol (2,3-BD) fermentation was carried out using an engineered S. cerevisiae strain. The use of HT acid-hydrolyzed medium with 1.9 g/l of 5-hydroxymethylfurfural showed a reduction in the lag time from 48 to 24 h. The 2,3-BD concentration and yield coefficient at 72 h were 14.8 g/l and 0.30, respectively. Therefore, HT acid hydrolysis and the use of the engineered S. cerevisiae strain can enhance the overall 2,3-BD yields from G. amansii seaweed.

• Journal of Microbiology and Biotechnology
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• 제30권6호
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• pp.930-936
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• 2020

The red seaweed Gracilaria verrucosa has been used for the production of bioethanol. Pretreatment for monosaccharide production was carried out with 12% (w/v) G. verrucosa slurry and 500 mM HNO₃ at 121℃ for 90 min. Enzymatic hydrolysis was performed with a mixture of commercial enzymes (Cellic C-Tec 2 and Celluclast 1.5 L; 16 U/ml) at 50℃ and 150 rpm for 48 h. G. verrucosa was composed of 66.9% carbohydrates. In this study, 61.0 g/L monosaccharides were obtained from 120.0 g dw/l G. verrucosa. The fermentation inhibitors such as hydroxymethylfurfural (HMF), levulinic acid, and formic acid were produced during pretreatment. Activated carbon was used to remove HMF. Wild-type and adaptively evolved Saccharomyces cerevisiae, Candida lusitaniae, and Kluyveromyces marxianus were used for fermentation to evaluate ethanol production.

• 한국식품영양과학회지
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• 제30권1호
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• pp.6-13
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• 2001

The study was conducted to investigate the effect of the browning inhibitors such as PVPP(polyvinylpoly-pyrrolidone), A.A.(ascorbic acid) on nonezymatic browning factors [free sugar, total amino acid, organic acid, A.A., HMF (hydroxymethylfurfural)] and enzymatic browning factors [PRO (polyphenoloxidase) activity, polyphenol compounds] in concentrated apple juice during 90 days storage. Considering color value (L value, $\Delta$E), absorbance at 420 nm, concentrated apple juice during 90 days storage. Considering color the effect of browning inhibition. According to the storage period, the changes of nonenzymatic factors in concentrated apple juice added with browning inhibitors were similar to those in control (concentrated apple juice without browning inhibitors), which were the decreased of sucrose(0.24~0.35% at 90 days), the slight increase of glucose and fructose, the decrease of total amino acid (530.4~573.1 mg/10g at 90 days), same value of A.A. at 90 days (38.5~78.6 mg/100g), and the increase of HMF (27.8~30.6 mg/100g at 90 days). On the contrary, enzymatic browning factors were significantly inhibited in concentrated apple juice added with PVPP, judging from the slow increase of PRO activity and the significant decrease of initial value in polyphenol compounds (especially chlorogenic acid). These results suggest that PVPP plays an important role as enzymatic browning inhibitor, that is, a scavenger of polyphenol compounds by adsorption in concentrated apple juice.

• Journal of Microbiology and Biotechnology
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• 제28권12호
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• pp.1999-2008
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• 2018

The compound 2,5-furandicarboxylic acid (FDCA), an important bio-based monomer for the production of various polymers, can be obtained from 5-hydroxymethylfurfural (HMF). However, efficient production of FDCA from HMF via biocatalysis has not been well studied. In this study, we report the identification of key genes that are involved in FDCA synthesis and then the engineering of Raoultella ornithinolytica BF60 for biocatalytic oxidation of HMF to FDCA using its resting cells. Specifically, previously unknown candidate genes, adhP3 and alkR, which were responsible for the reduction of HMF to the undesired product 2,5-bis(hydroxymethyl)furan (HMF alcohol), were identified by transcriptomic analysis. Combinatorial deletion of these two genes resulted in 85.7% reduction in HMF alcohol formation and 23.7% improvement in FDCA production (242.0 mM). Subsequently, an aldehyde dehydrogenase, AldH, which was responsible for the oxidation of the intermediate 5-formyl-2-furoic acid (FFA) to FDCA, was identified and characterized. Finally, FDCA production was further improved by overexpressing AldH, resulting in a 96.2% yield of 264.7 mM FDCA. Importantly, the identification of these key genes not only contributes to our understanding of the FDCA synthesis pathway in R. ornithinolytica BF60 but also allows for improved FDCA production efficiency. Moreover, this work is likely to provide a valuable reference for producing other furanic chemicals.

• 한국식품영양학회지
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• 제28권5호
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• pp.745-751
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• 2015

본 연구에서는 숙성 온도와 기간에 따른 마늘의 품질특성변화를 살펴보기 위하여 통마늘을 $60^{\circ}C$에서 60일간, $70^{\circ}C$에서 40일간 숙성 처리하여 pH, 총산도, 갈변도, 5-HMF 함량, fructose 함량, SAC 함량, 총 폴리페놀 함량 및 DPPH radical 소거활성 측정하였다. 숙성 온도가 높고 숙성 기간이 길어질수록 마늘의 pH는 감소하고, 총 산도, 갈변도 및 5-HMF 함량은 증가하는 경향을 보였다. 특히, 5-HMF 함량은 $60^{\circ}C$ 숙성 처리 시 0.08~3.30 mg/100 g으로 증가량이 적은 반면, $70^{\circ}C$ 숙성 처리 시 0.05~106.07 mg/100 g으로 숙성 25일차부터 급격히 증가하는 것으로 나타났다. Fructose 함량은 $60^{\circ}C$의 숙성온도에서는 0.77~14.57%으로 지속적으로 증가한 반면, $70^{\circ}C$ 숙성 온도에서는 30일차까지 1.07~19.75%까지 증가 후 15.11%로 감소하는 것으로 나타났다. SAC 함량은 생마늘의 경우 48.11 mg/100 g이었으며, $60^{\circ}C$에서 20일 숙성 시 100.50 mg/100 g으로, $70^{\circ}C$에서 5일 숙성 시 85.55 mg/100 g까지 증가한 후 숙성 기간이 경과할수록 SAC 함량은 감소하였다. 생마늘의 총 폴리페놀 함량은 98.38 mg/100 g이었고, $60^{\circ}C$ 숙성 처리 시 591.82 mg/100 g까지, $70^{\circ}C$ 숙성 처리 시에는 665.22 mg/100 g까지 생마늘에 비해 각각 6.01배 및 6.67배 증가하였다. DPPH radical 소거활성의 경우, 숙성 온도가 높고 숙성 기간이 길어질수록 증가하는 경향을 보였다. 따라서 마늘 섭취가 용이하고 항산화 활성이 우수한 숙성 마늘 제조를 위해서는 $70^{\circ}C$에서 30일, 숙성 마늘의 유효성분인 SAC의 다량 생산을 위해서는 $60^{\circ}C$에서 15일간 숙성 처리하는 하는 것이 적합할 것으로 판단되며, 이상의 결과는 항산화 효과가 강화 및 SAC 함량 증진 등 선택적인 숙성 마늘의 제조에 활용이 가능할 것으로 기대된다.

• 한국식품과학회지
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• 제31권4호
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• pp.894-898
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• 1999

둥굴레속 중에서도 흔하지 않는 용둥굴레(약초로 다룰 때는 옥죽이라고도 함)를 이용하여 제조되는 옥죽차를 사용하여 향기성분의 연구를 행하였다. 옥죽차의 제조법은 천성산 일대에서 인공재배하여 $4{\sim}5$년 자란 용둥굴레의 뿌리를 9번 찌고 9번 건조하는 방법인 9증 9포(九蒸九曝)법을 적용하는데, 그 제조 과정중의 향기성분을 단계별로 Likens and Nickerson의 연속증류추출법으로 추출하고, GC 및 GC-MS법으로 분석, 동정하였다. 그 결과 원재료에는 향기성분이 거의 없었으나, 찌고 덖는 과정을 거치는 동안 furfural, furfuryl alcohol, 2-acetylfuran, 5-methylfurfural, 5-hydroxymethylfurfural 및 2-methyl-dihydro-2(3Η)-furanone등과 methylpyrazine과 2,3-dimethylpyrazine 등의 pyrazine류, acetic acid 및 propionic acid등의 acid류가 생성되었다.

• Preventive Nutrition and Food Science
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• 제18권1호
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• pp.50-59
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• 2013

Black jujube was made by aging dried jujube and its physiochemical characteristics, antioxidant activities and ${\alpha}$-glucosidase inhibitory activities were evaluated. The moisture and sugar contents were increased depending on the period of aging times and the pH was reduced thereby increasing acidity. The color of black jujube extract was changed from red to black resulting in decreases of Hunter color values L, a and b. As the aging progressed, sucrose was decomposed by increasing glucose and fructose, indicating higher contents of the total reducing sugars. Among the six different types of organic acids extracted from dried jujube, the levels of oxalic acid and citric acid were increased as the aging progressed. The total polyphenol contents in ethanol and water extracts of dried jujube were 7.74 and 8.12 mg/g, respectively. The water extract of black jujube aged for 48 hr contained the highest polyphenol contents at 16.82 mg/g. The 5'-hydroxymethylfurfural (5'-HMF) contents of black jujube extract significantly increased by longer aging times, and contained higher contents in the ethanol extract than water extract. The ethanol extract of black jujube showed the highest 5'-HMF content with 338.89 mg% after aging for 3 days. Also, $IC_{50}$ values of black jujube aged for 72 hr evaluated by DPPH and ABTS radical assays were 0.54 and 0.59 mg/mL, respectively. ${\alpha}$-Glucosidase inhibitory activities of black jujube at the concentration of 3.33 mg/mL (ethanol extract) increased from 65 to 80 % after aging for 72 hr.

• Preventive Nutrition and Food Science
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• 제13권1호
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• pp.54-59
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• 2008

This study was conducted to investigate the effect of pH on the formation of furfural compounds from glucose and fructose reacting with amino acid enantiomers in the Maillard reaction. Hydroxymethylfurfural (HMF) content was highest at pH 4.0, and decreased with increasing pH. HMF was significantly higher in glucose-based systems than fructose-based systems. Furfuryl alcohol (FFA) and 5-methyl-2-furaldehyde (MF) were not increased with increasing pH, and only small amounts were formed. In addition, 2-furaldehyde (F) was found to increase in the systems, as pH increased. However, the content was small and variable. 2,5-Dimethyl-4-hydroxy-3(2H)-furanone (DMHF) was only found in Glc/D-Asn, Glc/L-Lys and Fru/D-Lys system, but the content was not increased with increasing pH. 2-acetylfuran (AF) was higher in Glc (or Fru)/L-Lys and Glc (or Fru)/D-Lys systems at pH 7.0. However, at pH 4.0, the content of AF was higher in the Glc (or Fru)/Gly and Glc (or Fru)/L-Asn systems. Therefore, this study aimed to observe the effect of pH, sugars and amino acid enantiomers on the production of furfural and related compounds by the Maillard reaction. A clear tendency was observed for some classes of compounds to be more easily formed at higher or lower pH. HMF was more readily formed at lower pH, while FFA, F, DMHF and MF were inhibited by acidic conditions. Particularly, compounds like FFA, F and MF were not affected by pH changes. In addition, DMHF and MF were only formed in L-Lys and D-Lys system.