• 한국생물공학회:학술대회논문집
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• 한국생물공학회 2005년도 생물공학의 동향(XVII)
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• pp.495-495
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• 2005

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2008년도 추계학술대회 논문집
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• pp.67-70
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• 2008

Biological conversion of biomass into fuels and chemicals requires hydrolysis of the polysaccharide fraction into monomeric sugars. Hydrolysis can be performed enzymatically, and with dilute or concentrate mineral acids. In this study, dilute sulfuric acid used as a catalyst for the hydrolysis of rapeseed straw. The purpose of this study is to optimize the hydrolysis process in a 15ml bomb tube reactor and investigate the effects of the acid concentration, temperature and reaction time on the hemicellulose removal and consequently on the production of sugars (xylose, glucose and arabinose) as well as on the formation of by-products (furfural, 5-hydroxymethylfurfural and acetic acid). Statistical analysis was based on a model composition corresponding to a $3^3$ orthogonal factorial design and employed the response surface methodology (RSM) to optimize the hydrolysis conditions, aiming to attain maximum xylose extraction from hemicellulose of rapeseed straw. The obtained optimum conditions were: acid concentration of 0.77%, temperature of $164^{\circ}C$ with a reaction time of 18min. Under these conditions, 75.94% of the total xylose was removed and the hydrolysate contained 0.65g $L^{-1}$ Glucose, 0.36g $L^{-1}$ Arabinose, 3.59g $L^{-1}$ Xylose, 0.51g $L^{-1}$ Furfural, 1.36g $L^{-1}$ Acetic acid, and 0.08g $L^{-1}$ 5-hydroxymethylfurfural.

• 한국식생활문화학회지
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• 제5권2호
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• pp.243-251
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• 1990

두릅나무 순의 saponin을 추출하여 그 구조를 밝혀 본 결과는 다음과 같다. 1. 자연산 날 것 식용적기의 crude saponin에서 aglycon으로 oleanolic acid와 hederagenin외에 1,3-methylenedioxy-3-dehydroxyoleanolic acid를 동정하였으며 당으로 ${\alpha},\;{\beta}-glucose$와 arabinose, rhamnose를 확인하였다. 2. 자연산 날 것 식용적기에 가장 많은 ‘b’ saponin(elatoside $Fh_2$)을 분리하여 동정한 결과 그 구조는 3-0-$[{\alpha}-L-arabinopyranosyl(1{\rightarrow}2)-{\beta}-D-glucopyranosyl]$-28-O-${\beta}-D-glucopyranosyl$ oleanolic acid라 추정된다.

• Journal of Microbiology and Biotechnology
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• 제18권3호
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• pp.434-442
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• 2008

We observed that an inclusion body (IB) of recombinant ${\beta}$-galactosidase that was produced by the araBAD promoter system in Escherichia coli (E. coil) showed enzyme activity. In order to improve its activity, the lowering of the transcription rate of the ${\beta}$-galactosidase structural gene was attempted through competition between an inducer (L-arabinose) and an inducer analog (D-fucose). In the deep-well microtiter plate culture and lab-scale fermentor culture, it was demonstrated that the addition of D-fucose caused an improvement in specific ${\beta}$-galactosidase production, although ${\beta}$-galactosidase was produced as an IB. In particular, the addition of D-fucose after induction led to an increase in the specific activity of ${\beta}$-galactosidase IB. Finally, we confirmed that the addition of D-fucose after induction caused changes in the structure of ${\beta}$-galactosidase IB, with higher enzyme activity. Based on these results, we expect that an improved enzyme IB will be used as a biocatalyst of the enzyme bioprocess, because an enzyme IB can be purified easily and has physical durability.

• 한국식품저장유통학회지
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• 제9권4호
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• pp.429-433
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• 2002

Candida sp. L-16 균주가 생산하는 D-xylulokinase는 배양균체를 초음파 파쇄한 조효소액으로 하여 황산암모늄 염석, DEAE-cellulose, chromatography, Sephadex G-100과 Sephadex G-200 gel filtration 과정으로 정제하여 최종 수율 11.2%로 약 23.2배 정제하였다. 정제 효소의 분자량은 SDS-PAGE로 분석한 결과 분자량은 75,000 dalton으로, Sephadex G-200겔 여과에 의해 150,000 dalton으로 나타나 dimer로 확인되었다. 효소 활성에 미치는 최적 반응 온도는 4$0^{\circ}C$로 나타났고, 온도안정성은 비교적 불안정하여 3$0^{\circ}C$이상에서는 빠르게 실활되었다. 정제 효소의 최적 반응 pH는 pH 8.0이었고, pH 7.0에서 pH 9.0 사이에서 비교적 효소활성이 높았다. 본 효소는 D-xylulose, D-arabinose, D-ribose등에서는 높은 기질특이성을 가지고 있었으나 D-xylose, D-glucose, L-arabinose 등은 기질로서 작용하지 못하였다. 정제 효소의 활성화 에너지값(Ea)은 $25^{\circ}C$ 내지 4$0^{\circ}C$$^{\circ}C$의 온도 범위에서 4.75kcal/mol이었다. 효소의 활성화제로는 EDTA, cysteine-HCl, DTT, glutathione 등이 존재하며 억제제로는 6-phosphogluconic acid, 2-koeto-gluconic acid 등으로 나타났다.

• Journal of Microbiology and Biotechnology
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• 제14권3호
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• pp.474-482
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• 2004

The $\alpha$-L-arabinofuranosidase (Arfase) gene of Bacillus stearothermophilus No. 236 was cloned and sequenced. The ORF of the gene, designated arfA, encoded a 507 -residue polypeptide with calculated molecular mass of 57 kDa. The Arfase produced by a recombinant Escherichia coli strain containing the arfA gene was purified to apparent homogeneity and characterized. The molecular mass of the Arfase determined by SDS-PAGE was 60 kDa. However, according to gel filtration, it was estimated to be approximately 190 kDa. These results indicated that the functional form of the Arfase is trimeric. The optimal pH and temperature for the enzyme activity were pH 6.5 and $55^{\circ}C$, respectively. The half-life of the enzyme at $60^{\circ}C$ was about 6 h. Kinetic experiments at $45^{\circ}C$ with pNPM (p-nitrophenyl $\alpha$-L-arabinofuranoside) as a substrate gave the $K_m and V_{max}$ values of 1.19 mM and 26.1 U/ mg, respectively. When the enzyme was combined with Bacillus stearothermophilus No. 236 endoxylanase and $\beta$-xylosidase, it hydrolyzed arabinoxylan into L-arabinose and xylose more efficiently than Arfase alone. This synergistic effect suggested that the complete hydrolysis of xylan with large amounts of arabinose side chains required Arfase as well as endoxylanase and $\beta$-xylosidase.

• Journal of Microbiology and Biotechnology
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• 제21권10호
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• pp.1053-1056
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• 2011

Optimal conditions for a high cell density fermentation were investigated in a recombinant Escherichia coli producing salmosin, a platelet aggregation inhibitor. The optimized carbon and nitrogen sources were glycerol 10 g/l, yeast extract 30 g/l, and bacto-tryptone 10 g/l, yielding the dry cell weight (DCW) of 10.61 g/l in a 500 ml flask culture. The late-stage induction with 1% L-arabinose in a 5 l jar fermentor showed the highest DCW of 65.70 g/l after 27 h of the fed-batch fermentation. Around 2,200 mg/l of the protein was expressed as an inclusion body that was then refolded to obtain the active salmosin of 96 mg/l. We also confirmed the inhibitory activity against platelet aggregation of the active salmosin from the high cell density fermentation.

• 미생물학회지
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• 제42권4호
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• pp.326-331
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• 2006

본 연구에서는 경기도 안양에 있는 하천에서 분리한 홍색 비황 광합성 세균Rhodopseudomonas sp. KH4에서 생성된 extracellular polysaccharide (EPS)의 중금속 흡착특성에 대해 연구하였다. 100 mg/L의 Cd과 Cu의 최적 흡착조건(온도$40^{\circ}C$ Cd; pH 8, Cu; pH 5)에서 1.0 g/L의 EPS를 첨가하였을 때, Cd의 경우 30분 동안 842 mg/L, Cu의 경우 10분 동안 70.0 mg/L가 흡착되었다. 또한 Cd과 Cu가 각각 100 mg/L씩 공존되어 있는 경우, pH 5, $25^{\circ}C$에서 EPS 1.0 g/L 첨가하였을 때 Cd과 Cu가 각각 16.8 mg/L, 48.7 mg/L가 흡착되었다. 또한 Langmuir 등은 흡착식으로 부터 EPS 1.0 g/L, pH 5, $25^{\circ}C$에서 Cd과 Cu의 흡착량은 각각 76.9 mg/L, 67.1 mg/L로 실제 경험치와 큰 차이를 보이지 않았다. 에탄올 침전법으로 정제된 KH4 strain으로부터 생성된 EPS는 gas-liquid chromatography (GLC) 분석에 의한 중성당 분석 결과, arabinose, glucose, mannose가 각각 2.4%, 7.1%, 90.5%로 mannose가 대부분을 구성하였다.

• Journal of Microbiology and Biotechnology
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• 제20권6호
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• pp.1018-1021
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• 2010

Metallic and non-metallic isomerases can be used to produce commercially important monosaccharides. To determine which category of isomerase is more suitable as a template for directed evolution to improve enzymes for galactose isomerization, L-arabinose isomerase from Escherichia coli (ECAI; E.C. 5.3.1.4) and tagatose-6-phosphate isomerase from Staphylococcus aureus (SATI; E.C. 5.3.1.26) were chosen as models of a metallic and non-metallic isomerase, respectively. Random mutations were introduced into the genes encoding ECAI and SATI at the same rate, resulting in the generation of 515 mutants of each isomerase. The isomerization activity of each of the mutants toward a non-natural substrate (galactose) was then measured. With an average mutation rate of 0.2 mutations/kb, 47.5% of the mutated ECAIs showed an increase in activity compared with wild-type ECAI, and the remaining 52.5% showed a decrease in activity. Among the mutated SATIs, 58.6% showed an increase in activity, whereas 41.4% showed a decrease in activity. Mutant clones showing a significant change in relative activity were sequenced and specific increases in activity were measured. The maximum increase in activity achieved by mutation of ECAI was 130%, and that for SATI was 190%. Based on these results, the characteristics of the different isomerases are discussed in terms of their usefulness for directed evolution of non-natural substrate isomerization.

• 생물환경조절학회지
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• 제15권1호
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• pp.91-99
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• 2006

This study was conducted to determine the influence of postharvest dipping treatment with aminoethoxyvinylglycine (AVG) on ethylene production and composition of non-cellulosic neutral sugars in cell walls of 'Tsugaru' apple fruits during storage. Fruits were harvested on August 20, soaked in AVG 50 and 75 $mg L^{-1}$ solution for 5 minutes, and stored in cold storage chamber at $0{\pm}1^{\circ}C$ for 60 days. Fruit quality factor, ethylene productions, and cell wall component changes were investigated at 20 days interval. As a result, the fruit firmness and acid content were much higher in AVG treated fruits than those of untreated one during 60 days of cold storage. Ethylene production of AVG treated fruits was reduced to the level of 1/10 compared with untreated one. As to the change of non-cellulosic neutral sugars in the cell walls of 'Tsu- garu' fruits, the major sugar was arabinose and galactose in water, CDTA and $Na_2CO_3$ soluble fractions. The content of arabinose and galactose in untreated fruits increased as the softening of fruits was in progress, but the fruits treated with AVG showed a little change during storage, so it is predicted that these two cell wall compositional sugars were not solubilized by the treatment of AVG. Accordingly, the marketability of 'Tsu- garu' fruits could remarkably increase when soaking the fruits in AVG solution after harvest.