Earticle

본 연구는 바이오디젤 제조를 위한 원료로서 커피찌꺼기(spent coffee grounds, SCG)를 이용하여 바이오디젤로 전환 하기 위한 반응 조건을 최적화하고자 한다. SCG에서 추출한 오일은 3.3%의 높은 유리지방산(free fatty acid, FFA)을 함 량하고, 이를 낮추기 위한 방법으로 산 촉매와 알칼리 촉매 전처리를 비교하였다. 산 촉매는 알칼리 촉매보다 효과적이고, 반응 후 오일의 수율은 98%이다. 산 촉매 전처리에 관련된 주요 인자를 반응표면분석법으로 최적화한 결과, 최적반응조 건은 0.87% H2SO4, 21.2% methanol, 74.7oC이고, 이 조건에서 예상되는 산가(Acid value, AV)는 1.40 mgKOH/g (FFA 0.7%)이다. 전처리된 SCG 오일을 바이오디젤로 전환하는 촉매로 KOH는 가장 효율적이다. 최적반응조건인 methanol 몰 비 6:1, 1.25% KOH, 65oC에서 생성된 fatty acid methyl ester 함량을 정량한 결과 97 ~ 98% 전환율을 보였다.

This study used spent coffee grounds (SCG) for producing biodiesel and was aimed at optimizing reaction conditions for converting to biodiesel. Two pretreatment methods using acid and alkali catalysts were examined to reduce high free fatty acid (FFA) content of 3.3% in the oil extracted from SCG. It was ascertained that acid catalyst was effective compared with alkali, showing the yield of 98%. And then the factors related in acid-catalyzed esterification were optimized using response surface methodology. The optimal reaction conditions were 0.87% sulfuric acid, 21.2% methanol, and a temperature of 74.7oC. Under these conditions, the expected FFA content was 0.7%. Alkali-catalyzed transesterification using KOH efficiently converts pretreated SCG oil to biodiesel. At the experimental optimal conditions (methanol to oil molar ratio of 6:1, 1.25% KOH, and 65oC), a conversion ratio of 97-98% was confirmed based on the generated fatty acid methyl ester.

Water, as a reaction solvent, has received considerable attention in synthetic organic chemistry due to being low-cost and green. In this study, green esterification of Kraft lignin and oleic acid at room temperature was investigated, and only water was used as a reaction solvent. A surfactant-combined system (p-toluenesulfonic acid/4-dodecylbenzenesulfonic acid) was designed to simultaneously solubilize lignin and disperse oleic acid, producing microreactors for esterification. After the reaction, adding water into the reaction mixture could easily precipitate the lignin ester. Its yield was 30.3 ± 0.9%. The lignin ester was characterized by 1H NMR, FT-IR, GPC, TGA, DSC, PSA, and contact angle analyzer. The results showed the successful esterification of lignin and oleic acid, indicating the effectiveness and feasibility of esterification of macromolecules in water. Due to long oleyl chains substituting hydroxyl groups of lignin, the lignin ester showed a significant decrease in glass transition temperature, an obvious increase in contact angle, and exhibited excellent thermoplasticity and hydrophobicity. Additionally, the result of PSA showed some lignin-ester particles fell in the nano-size range.

Candida rugosa lipase를 이용하여 효소 농도, 반응온도, 알콜 농도 및 종류 등의 반응조건에 따른 racemic ibuprofen 에 스테르화 반응의 초기반응속도, 전환율 그리고 입체 선택성을 조사하였다. 제조된 S-(+)-ibuprofen alkyl ester는 황산을 촉매로 하는 가수분해반응에 의해 순수한 S-(+)-ibuprofen으로 전환되었다. 에스테르화 반응에서는 반응온도 60℃에서 최대 활성을 보였으며, 그 이상의 온도에서는 효소의 활성 저하로 전환율과 enantiomeric excess값이 동시에 현격하게 감소하는 경향을 보였다. 알코올 농도가 증가할수록 알콜의 효소반응 저해제 작용으로 인하여 초기반응속도가 감소하는 경향을 보였으며, 최종 전환율은 Ibuprofen와 Alcohol의 몰 비가 1/1에서 최고 값을 나타냈다. 알콜 종류에 따른 알코올 체인 길이가(C2～C10) 증가할수록 전환율은 증가하였는데, 특히 알코올 체인 길이가 가장 큰 데칸올이 가장 높은 전환율을 보였다. 반응온도가 60℃ 이상의 높은 경우를 제외하고 에스테르화 반응조건에 따라 입체 선택성 즉 enantiomeric excess의 큰 변화는 없었다. 화학적 가수분해 반응은 비교적 짧은 반응시간(3시간)내에 평형반응에 도달하였으며, 알코올 체인 길이에 관계없이 거 의 95% 이상의 높은 전환율 및 입체 선택성을 나타냈다. Lipase에 의한 ibuprofen 에스테르화 반응의 최적 조건과 화학적인 가수분해 반응을 통해서 racemic ibuprofen으로부터 높은 수율의 S-(+)-ibuprofen을 확보할 수 있었다.

The enantioselective esterification of racemic ibuprofen catalyzed by a Candida rugosa lipase was studied according to reaction conditions such as a lipase concentration, reaction temperature, alcohol chain length and alcohol concentration. The S-(+)-ibuprofen alkyl esters prepared were converted to S-(+)-ibuprofen by hydrolysis with sulfuric acid as a catalyst. High conversions in the esterifications were obtained at 60℃ and an equimolar ratio of octanol to ibuprofen. The initial reaction rate of the esterification decreased with increasing octanol concentration. Conversion and initial reaction rate increased with increasing alcohol chain length. Values of enantiomeric excess(ee) according to esterification reaction conditions did not change below 60℃. On the other hand, values of conversion and ee for the chemical hydrolysis of S-(+)-ibuprofen alkyl esters were independent of alcohol alkyl chain length. Optical resolution of racemic ibuprofen was achieved by lipase catalyzed esterification and chemical hydrolysis. The separation method provided a high yield and enantioselectivity for the production of S-(+)-ibuprofen from racemic ibuprofen.

Enzymatic syntheses of sugar fatty acid (FA) esters are important because of their wide range of applications in the food, cosmetic, and pharmaceutical industries. These molecules are commonly synthesized from F As and mono-, or di-saccharides by chemical or enzymatic esterification. Previously, sugar esters were produced using oligosaccharide, and interfacial tension values and inhibitory effects towards tumor cell lines were improved when higher DP saccharides were used. In this study, the direct esterification of maltoheptaose (G7) with vanous length of F As was investigated by the catalytic action of Candida antartica lipase B. Among the F As palmitic acid (PA) was the best substrate for the G7 ester formation. Optimal reaction conditions including solvent composition and molar ratio of G 7: P A were established for the G7-PA. The conversion yield and sugar ester structure were analyzed using various instrumental analyses. The results showed that G7-PA monoester was successfully synthesized with a molar ratio of I :20 (G7: PA) in I 0% DMSO of t-butanol at 60°C, and the conversion yield was over than 21%. The position of ester bond formation was identified that PA was attached to C-6 of the reducing end glucosyl moiety. The melting temperature of G7- PA monoester was reached at 56 °C, lower than that of pure G7 and PA. In addition, the G7- p A esters and commercial sucrose esters were compared as emulsifiers. Both type of sugar esters prevented coalescence during 7 days and showed good emulsifying properties in 0/W emulsions since the droplets diameter did not have significant change during the storage.

Liquefied-wood polymer composite was prepared and mechanical properties was evaluated to develop potential utility of liquefied wood. The liquefied wood was made from waste wood and chemical modified with acetic anhydride and maleic anhydride (MA), phtalic anhydride (PA). The composite sheet was prepared from modified liquefied-wood and polymer(PE). The mechanical, chemical and microscopical properties composite sheet were investigated. The results were summarized as follows, 1. The tensile strength was increased and breaking elongation of composite sheet was decreased with the time of acetylation and the dosage of MA. 2. The Young's modulus of composite sheet was gradually decreased with the dosage of PA. 3. The peak intensity of 1737cm-1 in FT-IR spectra of chemical modified liquefied woods was increased. 4. The dispersity of liquefied woods with PE was improved with chemical modification.

양잠누에 (Bombyx mori)의 고치에서 생산되는 섬유 단백 질인 피브로인은 대부분의 단백질과 달리 크기가 작은 아미 노산인 글리신 (glycine) 알라닌 (alanine) 세린 (serine)의 조 성비가 각각 48, 32 및 11%로 전체의 91%를 차지하며 [1], 글리신과 알라닌, 세린 및 타이로신 (tyrosine)이 교대로 치환 된 Gly-X (X: Ala 65%, Ser 23%, Tyr 9%)가 반복되는 아미노산 서열 구조를 가지고 있다 [2]. Jeong 등 [3]은 이와 같이 아미노산 서열이 반복되는 특성을 이용하여 피브로인을 파파인으로 가수분해하여 [Gly - X]n - (n = 2, 4, 6 및 8)인 짝수의 올리고 펩타이드가 대부분인 가수분해물을 얻을 수 있다고 보고하였다. 다른 단백질의 가수분해물의 펩타이드 조성은 매우 다양한 반면, 피브로인 가수분해물은 매우 제한 적인 종류의 짝수 펩타이드로 주로 구성되어 있고 산업적 인 수준으로 대량 얻을 수 있어 다양한 정밀화학제품의 원료 로 활용할 수 있을 것으로 예상된다. 예를 들어 펩타이드와 글리세리드 (glyceride)가 결합한 1-peptidyl-2-arachidonoyl- 3-stearoyl-sn-glyceride는 양의 혈청에서 발견되는 면역활성 물질이다 [4]. 이와 같이 지방산의 종류나 펩타이드의 종류를 달리하여 다양한 펩타이드 글리세리드를 합성할 수 있고, 이들 중에는 특별한 생리활성을 가지는 펩타이드 글리세리드 가 있을 수 있으나, 아직까지 이와 같은 다양한 펩타이드 글 리세리드를 합성한 보고는 없다. 현재까지는 펩타이드 대신 아미노산 글리세리드가 새로운 바이오 계면활성제로서 개발 할 목적으로 효소적인 방법으로 합성된 바 있다 [5]. 펩타이 드 혼합물을 효소적으로 가공하여 기능을 개선시키는 방법은 알려져 있으나, 이 과정에서 각각의 펩타이드의 조성의 변화 를 질랑분석기를 이용하여 추적한 결과는 보고된 바 없다. 그리고 혼합물의 특성상 여러 종류의 기질이 단일 효소와 반응하는 경우, 효소 반응의 특성, 기질특이성에 따른 펩타 이드 혼합물의 조성의 변화 및 이 과정에서 효소의 기질 특이성을 역추적할 수 있다. 따라서 본 연구에서는 피브로인 펩타이드를 효소적으로 수 식하여 펩타이드 글리세리드를 합성하는 중간단계로 파파인 을 이용하여 글리세롤 에스터화 반응을 통하여 피브로인 펩 타이드의 글리세릴 에스터를 합성하는 반응을 수행하였다. 특히 파파인은 펩타이드 가수분해 활성뿐만 아니라 에스터 분해효소 (esterase)의 활성을 동시에 가지고 있으므로 [6], 효소적으로 에스터를 합성하는데 사용되어 왔다. 그동안 파 파인은 유기용매가 첨가된 조건하에서 주로 아미노산인 알라 닌을 알코올류를 에스터 결합시키거나 [7], 펩타이드에 에탄 올을 에스터 결합시키거나 [8] 혹은 D, L 아미노산의 분활하 는데 [9] 사용되었다. 이후 Mintin 등 [10]은 파파인으로 N 말단이 보호된 여러 종류의 아미노산에 글리세롤을 에스터 결합시키는 반응을 성공하였다. 효소적 에스터화 반응의 촉 매로 빈번하게 사용되는 트립신과 달리 파파인은 넓은 기질 특이성 [11]을 가지고 있으므로 다양한 기질에 글리세릴 에스 터를 형성할 수 있을 것으로 예상된다. 따라서 본 연구에서는, 파파인으로 가수분해된 피브로인 펩타이드에 추가적으로 글리세롤을 공급하고 반응조건을 변화시켜 피브로인 펩타이드에 글리세릴 에스터 결합을 형성시키는 역반응을 시도하였다. 에스터 결합을 형성하기 위해서는 카복실기가 해리되지 않은 상태에서 -COOH의 OH기가 효소의 활성부위의 아미노산의 잔기와 수소결합 을 형성한 후 분리되어야 하므로, 에스터화 반응은 펩타이 드의 카복실기의 pKa 값보다 충분히 낮은 pH 3에서 과량 의 글리세롤을 첨가하여 반응시키고 각각의 펩타이드의 글리세릴 에스터의 생성 여부는 전기분무 이온화형 질량분 석기 (ESI-MS)를 이용하여 분석하였다. 아울러 생성된 글리 세릴 에스터는 카복시 말단이 에스터화되어 중성용액에서 양전하를 띠는 점을 활용하여 이온교환수지 칼럼을 이용 하여 회수하였다.

Papain hydrolysate of fibroin was found to be mainly composed of several even-numbered peptides that can be produced at a large scale and can be used as a precursor for biological fine-chemicals such as peptide detergents. Thus, the hydrolysate was further modified to synthesize a peptide mixture of glyceryl esters using the identical enzyme for the production of such chemicals. Formation of glyceryl ester of each peptide was confirmed by identifying peaks of the nominal mass shift of +74 Da in mass spectrometry. Analysis of the mass spectra indicated that glyceryl esters of di- and tetra-peptides were the major constituents of the mixture and that alanylglycine was most preferentially esterified. It also suggests that papain prefers dipeptide to tetrapeptide and alanine to serine or tyrosine at P2 position as substrate for glyceryl esterification. The glyceryl esters were recovered using ion exchange resin and the yield of glyceryl esterification recorded was 17.8% by weight.

Ac-Tyr-OH의 에스테르화 반응은 water/water­m miscible organic solvent를 이용하여 단일상계 (one phase system) 조건 하에서 -achymotrypsin의 촉 매작용으로 진행하였으며, 그 결과는 다음과 같다. Ac- Tyr-OH(1OmM)이 함유된 에탄올(lOml)[ 4 % %(v/v) buffer 함유] 용액에서 a-chymotrypsin의 촉매작용에 의한 에스테르화 반응에 영향을 마치는 흡착물질 chitin, chitosan, Sephadex G-25 및 G-50, CM 및 DEAE-Sephadex, CM 및 DEAE cellulose 중 chitin을 첨가하였을 경우, 에스테르화 수율이 62%로 가장 높았다. 그리고 에스테르화 수 율에 마치는 최적반응조건은 chitin/a-chymotry psm의 비가 20(w/w), 온도35℃ , pH 8.0 빛 유기 용매에 첨가된 수용액의 농도는 2%(v/v)였다. 또한, water/water-miscible organic solvent system 에서 chitin의 첨가는 효소의 안정성에 기여하는 것으로 나타났다. 최적반응조건 하에서 에스테르화 반응의 수율, Km 및 Vmax 값은 각각 93%, 3.093mM 및 1.088mM/mg/hr이었다.

The esterification of Ac-Tyr-OH was carried out in one-phase system containing ethanol by -chymotrypsin. The results of the esterification reaction are as follows. Chitin-a-chymotrypsin complex was found to be an effective catalyst for the esterlfication of Ac-Tyr-OH in ethanol organic solvent. The optimal conditions for the esterification were chitn/-chymotrypsin ratio, 20(w/w); reaction temp.,35℃ ; reaction pH, 8.0; reaction time, 24 hrs. Also, addition of chitin in water/water-miscible organic solvent was effective for the stability of the enzyme. The esterification yield, Km and Vmax under optimal conditions were 93%, 3.093mM and 1.088mM/mg/hr, respectively.

methacrylic acid과 ethylene glycol과의 에스테르화 반응을 ZSM-5에 지지된 heteropolyacids [HPA: $H_4SiW_{12}O_{40}$(STA)와 $H_3PW_{12}O_{40}$(PTA)] 하에서 수행하였다. 비교를 위하여, 지지하지 않은HPA, $H_2SO_4$, $BF_3$와 PTSA 하에서 같은 반응을 수행하였다. 연구한 촉매 중에서, HPA는 $H_2SO_4$, $BF_3$와 PTSA와 비교하여 더 좋은 활성을 보여주었다. 촉매 활성을 HPA지지 ZSM-5 촉매와 비교하였는데, 그 결과 ZSM-5위에 지지된 30 wt% PTA는 bulk PTA와 거의 같은 활성을 나타내었다. 이 반응은 methacrylic acid에 관하여 1차 속도 법칙을 따랐으며, 반응 생성물은 $^1H$-NMR과 FT-IR을 이용하여 확인하였다.

Esterification of methacrylic acid with ethylene glycol was carried out over Heteropolyacids [HPA: $H_4SiW_{12}O_{40}$ (STA) and $H_3PW_{12}O_{40}$ (PTA)] supported on ZSM-5. For comparison, the same reaction was carried out over unsupported HPA, $H_2SO_4$, $BF_3$ and PTSA. Among the catalysts studied, HPA showed better activity compared to $H_2SO_4$, $BF_3$ and PTSA. Catalytic activity was compared with HPA supported ZSM-5 catalysts. Typical results indicated that 30 wt% PTA supported on ZSM-5 showed nearly the same activity as that of bulk PTA. It was found that the reaction follows first order kinetics with respect to methacrylic acid. The reaction products were identified by $^1H$-NMR and FT-IR.

esters of the acid analytes were synthesized using $H_2SO_4$ as the catalyst. Efficiency of derivatization and instrumental molecular-response were compared with herbicides methylated with $BF_3-methanol$(14% W/V), $H_2SO_4-methanol$(33% V/V), and diazomethane. The molecular integrity of TFE-2,4-D, TFE-dicamba, and TFE-mecoprop, in the mixture, was confirmed by the GC/MSD method. The TFE-Esterification efficiency was maximized by adjusting the volume of $H_2SO_4$ the reaction time, and temperature. Optimal efficiency for the herbicide mixture was obtained by adding 1 ml of $H_2SO_4$ and 1 ml of TFE to the dried sample and allowing the reaction to proceed at $22^{\circ}C$ for 8 hr or using 0.5 ml $H_2SO_4$ and 1 ml of TFE at $60^{\circ}C$. For 120 min increasing the temperature and decreasing the reaction time were required for maximum esterification efficiency. The sensitivity of the GC/ECD to the TFE esters was about $2{\sim}20$ times greater than that to the methyl ester derivatives. The herbicides were extracted and esterified to TFE derivatives simultaneously from soil leachates previously spiked with the analytes. Herbicide recovery, peak resolution, and detector sensitivity were excellent without using column cleanup procedures.

The four different preparative methods of ${\alpha}-benzyl\;and\;{\beta}$-benzyl esters of N-benzyl-L-aspartic acid from L-aspartic acid are described.

Racemic N-benzylaspartic acid (4) was prepared from maleic anhydride and used to modify and develop some efficient methods for the preparation of N-benzylaspartic anhydride hydrobromide (5). Thus, successive treatment of the compound 4 with 30% HBr in acetic acid and acetic anhydride afforded the title compound 5 in 75% yield. From this compound 5, ${\alpha}$-benzyl and ${\alpha}$-methyl N-benzylaspartates were also prepared.

A lipase-catalyzed esterification reaction of (S)-naproxen ethyl ester by CALB (Candida antarctica lipase B) enzyme was performed in supercritical carbon dioxide. Experiments were performed in a high-pressure cell for 10 h at a stirring rate of 150 rpm over a temperature range of 313.15 to 333.15 K and a pressure range of 50 to 175 bar. The productivity of (S)-naproxen ethyl ester was compared with the result in ambient condition. The total reaction time and conversion yields of the catalyzed reaction in supercritical carbon dioxide were compared with those at ambient temperature and pressure. The experimental results show that the conversion and reaction rate were significantly improved at critical condition. The maximum conversion yield was 9.9% (216 h) at ambient condition and 68.9% (3 h) in supercritical state. The effects of varying amounts of enzyme and water were also examined and the optimum condition was found (7 g of enzyme and 2% water content).

Microemulsions gelled by the aid of natural polymers, i.e. microemulsion-based organogels (MBGs), have become of interest as novel tools for enzyme immobilization in hydrophobic solvents [1,2]. Sodium bis(2-ethylhexyl) sulfosuccinate (AOT)is frequently employed as an amphiphile for stable MBG formation.(omitted)

Atom-economical esterification is of great importance in green chemistry. In this work, we demonstrated the catalyst and additive free esterification of alcohols by their reaction with 2-acyl-4,5-dichloropyridazin-3(2H)-ones without solvent at $100^{\circ}C$. Aliphatic and aromatic alcohols were converted into the corresponding esters in good to excellent yields. It is noteworthy that the reaction is solvent-free, atom-economic, easy-workup, and rapid and that the process is inexpensive.

The first esterification reactor in the continuous polymerization of poly(ethylene terephthalate) has been analyzed by solving the material balances for the two-phase system with respect to the solubility of terephthalic acid. The Newton-Raphson method was used to solve the material balance equations instead of the Simplex method that is frequently used for finding a minimum point of a residual rather than a solution of an equation. A solution for the material balance equations, with the constraint of non-zero liquid phase fraction, could not be obtained with the solubility data of Yamada et al., but could be obtained with solubilities over a minimum value that is larger than their data. Thus, the solubility data of Yamada et al. are considered to be too small. On the other hand, the solubility data of Baranova and Kremer are so large that they gave a solution with the liquid phase only. Based on our results, several typical solubility curves satisfying the constraint of a non-zero liquid phase fraction are suggested in this study; we studied the reaction characteristics of the system using these curves. A higher temperature and a lower pressure are preferred for reducing the content of diethylene glycol.