Optimization of lipase-catalyzed synthesis of octyl hydroxyphenylpropionate by response surface methodology

Biosynthesis of diisooctyl 2,5-furandicarboxylate by Candida antarctica lipase B (CALB) immobilized on a macroporous epoxy resin

Diisooctyl 2,5-furandicarboxylate (DEF), an ester derivative of 2,5-furandicarboxylic acid (FDCA, a bio-based platform chemical), resembles the physical and chemical properties of phthalates. Due to its excellent biodegradability, DEF is considered a safer alternative to the hazardous phthalate plasticizers. Although FDCA esters are currently mainly produced by chemical synthesis, the enzymatic synthesis of DEF is a green, promising alternative. The current study investigated the biosynthesis of DEF by Candida antarctica lipase B (CALB) immobilized on macroporous resins. Out of five macroporous resins (NKA-9, LX-1000EP, LX-1000HA, XAD-7HP, and XAD-8) evaluated, the LX-1000EP epoxy resin was identified as the best carrier for CALB, and the XAD-7HP weakly polar resin was identified as the second best. The optimal immobilization conditions were as follows: CALB (500 μL) and LX-1000EP (0.1 g) were incubated in phosphate butter (20 mM, pH 6.0) for 10 h at 35°C. The resulting immobilized CALB (EP-CALB) showed an activity of 639 U/g in the hydrolysis of p-nitrophenyl acetate, with an immobilization efficiency of 87.8% and an activity recovery rate of 56.4%. Using 0.02 g EP-CALB as the catalyst in 10 mL toluene, and the molar ratio of 2,5-dimethyl furanediformate (1 mmol/mL) and isooctyl alcohol (4 mmol/mL) that was 1:4, a DEF conversion rate of 91.3% was achieved after a 24-h incubation at 50°C. EP-CALB had similar thermal stability and organic solvent tolerance compared to Novozym 435, and both were superior to CALB immobilized on the XAD-7HP resin. EP-CALB also exhibited excellent operational stability, with a conversion rate of 52.6% after 10 repeated uses. EP-CALB could be a promising alternative to Novozym 435 in the biomanufacturing of green and safe plasticizers such as DEF.

Highly Efficient Synthesis of Chlorogenic Acid Oleyl Alcohol Ester under Non-Catalytic and Solvent-Free Conditions

As a natural polyphenolic compound, chlorogenic acid (CGA) has attracted increasing attention for its various biological activities, such as antioxidant, liver protection, intestinal barrier protection, and effective treatment of obesity and type II diabetes. However, the poor solubility of CGA in hydrophobic media limits its application in the food, drug and cosmetic industries. In order to obtain new hydrophobic derivatives, a highly efficient synthesis approach of CGA oleyl alcohol ester (CGOA) under non-catalytic and solvent-free conditions was developed in this study. The influences of reaction temperature, reaction time, substrate molar ratio, and stirring rate on the CGA conversion were investigated. The results showed that the optimal conditions were as follows: reaction temperature 200 °C, reaction time 3 h, molar ratio of CGA to oleyl alcohol 1:20, and stirring rate 200 rpm. Under these conditions, the CGA conversion could reach 93.59%. Then, the obtained crude product was purified by solvent extraction and column chromatography, and the purify of CGOA was improved to 98.72%. Finally, the structure of CGOA was identified by FT-IR, HPLC-MS and NMR. This study provides a simple and efficient strategy for the preparation of CGOA with the avoidance of catalysts and solvents.

Catalytic Routes to Produce Polyphenolic Esters (PEs) from Biomass Feedstocks

Polyphenolic esters (PEs) are valuable chemical compounds that display a wide spectrum of activities (e.g., anti-oxidative effects). As a result, their production through catalytic routes is an attractive field of research. The present review aims to discuss recent studies from the literature regarding the catalytic production of PEs from biomass feedstocks, namely, naturally occurred polyphenolic compounds. Several synthetic approaches are reported in the literature, mainly bio-catalysis and to a lesser extent acid catalysis. Immobilized lipases (e.g., Novozym 435) are the preferred enzymes thanks to their high reactivity, selectivity and reusability. Acid catalysis is principally investigated for the esterification of polyphenolic acids with fatty alcohols and/or glycerol, using both homogeneous (p-toluensulfonic acid, sulfonic acid and ionic liquids) and heterogeneous (strongly acidic cation exchange resins) catalysts. Based on the reviewed publications, we propose some suggestions to improve the synthesis of PEs with the aim of increasing the greenness of the overall production process. In fact, much more attention should be paid to the use of new and efficient acid catalysts and their reuse for multiple reaction cycles.

One-pot synthesis of highly functionalized pyrimido[1,2-b]indazoles via 6-endo-dig cyclization

An efficient synthesis of nitrogen ring junction pyrimido-indazoles has been developed.

Green and efficient production of octyl hydroxyphenylpropionate using an ultrasound-assisted packed-bed bioreactor

A solvent-free system to produce octyl hydroxyphenylpropionate (OHPP) from p-hydroxyphenylpropionic acid (HPPA) and octanol using immobilized lipase (Novozym® 435) as a catalyst in an ultrasound-assisted packed-bed bioreactor was investigated. Response-surface methodology (RSM) and a three-level-three-factor Box-Behnken design were employed to evaluate the effects of reaction temperature (x  1), flow rate (x  2) and ultrasonic power (x  3) on the percentage of molar production of OHPP. The results indicate that the reaction temperature and flow rate were the most important variables in optimizing the production of OHPP. Based on a ridge max analysis, the optimum conditions for OHPP synthesis were predicted to consist of a reaction temperature of 65°C, a flow rate of 0.05 ml/min and an ultrasonic power of 1.74 W/cm2 with a yield of 99.25%. A reaction was performed under these optimal conditions, and a yield of 99.33 ± 0.1% was obtained.

Optimization of ultrasound-accelerated synthesis of enzymatic caffeic acid phenethyl ester by response surface methodology

The ultrasound-accelerated enzymatic synthesis of caffeic acid phenethyl ester (CAPE) from caffeic acid and phenethyl alcohol was investigated in this study. A commercial immobilized lipase from Candida antarctica, called Novozym® 435, was used as the catalyst. A 5-level-4-factor central-composite rotatable design (CCRD) and response surface methodology (RSM) were employed to evaluate the effects of reaction time, substrate molar ratio, enzyme amount, and ultrasonic power on percent molar conversion of CAPE. The results indicated that reaction time, substrate molar ratio, and ultrasonic power significantly affected percent molar conversion, whereas enzyme amount did not. A model for synthesis of CAPE was established. Based on ridge max analysis, the optimum condition for CAPE synthesis was predicted to be reaction time 9.6 h, substrate molar ratio 1:71, enzyme amount 2938 PLU, and ultrasonic power 2 W/cm(2) with the molar conversion value of 96.03 ± 5.18%. An experiment was performed under this optimal condition and molar conversion of 93.08 ± 0.42% was obtained.

Optimized enzymatic synthesis of caffeic acid phenethyl ester by RSM

In this study, optimization of enzymatic synthesis of caffeic acid phenethyl ester (CAPE), catalyzed by immobilized lipase (Novozym 435) from Candida antarctica was investigated. Novozym 435 was used to catalyze caffeic acid and 2-phenylethanol in an isooctane system. Response surface methodology (RSM) and 5-level-4-factor central-composite rotatable design (CCRD) were employed to evaluate the effects of synthesis parameters, such as reaction temperature (30-70 degrees C), reaction time (24-72 hours), substrate molar ratio of caffeic acid to 2-phenylethanol (1:10-1:90) and enzyme amounts (100-500 PLU) on percentage conversion of CAPE by direct esterification. Reaction temperature and time had significant effects on percent conversion. On the basis of ridge max analysis, the optimum conditions for synthesis were: reaction time 59 hours, reaction temperature 69 degrees C, substrate molar ratio 1:72 and enzyme amount 351 PLU. The molar conversion of predicted values and actual experimental values were 91.86+/-5.35% and 91.65+/-0.66%, respectively.

Lipophilic (hydroxy)phenylacetates by solvent-free lipase-catalyzed esterification and transesterification in vacuo

Various long-chain alkyl (hydroxy)phenylacetates were prepared in high yield by lipase-catalyzed transesterification of the corresponding short-chain alkyl hydroxyphenylacetates and fatty alcohols in equimolar ratios. The reactions were performed in vacuo at moderate temperatures in the absence of solvents and drying agents in direct contact with the reaction mixture. Immobilized lipase B from Candida antarctica (Novozym 435) was the most effective biocatalyst for the various transesterification reactions. Generally, Novozym 435-catalyzed transesterifications of short-chain alkyl (hydroxy)phenylacetates with long-chain alcohols led to higher conversions and enzyme activities than the corresponding esterifications. For example, the transesterification activity was up to 4-fold higher than the esterification activity for the formation of oleyl 4-hydroxy-3-methoxyphenylacetate using Novozym 435 as a biocatalyst. The relative transesterification activities were as follows: phenylacetate > 3-methoxyphenylacetate approximately 4-methoxyphenylacetate > 4-hydroxy-3-methoxyphenylacetate > 3-hydroxyphenylacetate approximately 4-hydroxyphenylacetate >> 2-methoxyphenylacetate >> 3,4-dihydroxyphenylacetate. With respect to the position of methoxy and hydroxy substituents, the transesterification activity of Novozym 435 decreased in the order meta approximately para >> ortho. Compounds with inverse chemical structures, for example, tyrosyl oleate, were obtained by Novozym 435-catalyzed esterification and transesterification of fatty acids and their methyl esters, respectively, with 2-phenylethan-1-ols. In contrast to the transesterifications of short-chain alkyl (hydroxy)phenylacetates with fatty alcohols, higher conversions and enzyme activities were observed for the Novozym 435-catalyzed esterifications of (hydroxy)phenylethanols with long-chain fatty acids than the corresponding transesterifications with fatty acid methyl esters.

Solvent-free enzymatic preparation of feruloylated monoacylglycerols optimized by response surface methodology

The ability of immobilized lipase B from Candida antarctica (Novozym 435) to catalyze the direct esterification of glyceryl ferulate (FG) and oleic acid for feruloylated monoacylglycerols (FMAG) preparation in a solvent-free system was investigated. Enzyme screening and the effect of glycerol on the initial reaction rate of esterification were also investigated. Response surface methodology (RSM) was used to optimize the effects of the reaction temperature (55-65 degrees C), the enzyme load (8-14%; relative to the weight of total substrates), oleic acid/(FG + glycerol) (6:1-9:1; w/w), and the reaction time (1-2 h) on the conversion of FG and yield of FMAG. Validation of the RSM model was verified by the good agreement between the experimental and the predicted values of FG conversion and FMAG yield. The optimum preparation conditions were as follows: temperature, 60 degrees C; enzyme load, 8.2%; substrate ratio, 8.65:1 (oleic acid/(FG + glycerol), w/w); and reaction time, 1.8 h. Under these conditions, the conversion of FG and yield of FMAG are 96.7 +/- 1.0% and 87.6 +/- 1.2%, respectively.

Optimal formation of hexyl laurate by Lipozyme IM-77 in solvent-free system

A medium-chain ester, hexyl laurate, with fruity flavor is primarily used in personal care formulations as an important emollient for cosmetic applications. To conform to the "natural" interests of consumers, the ability of immobilized lipase from Rhizomucor miehei (Lipozyme IM-77) to catalyze the direct esterification of hexanol and lauric acid by using a solvent-free system was investigated in this study. Response surface methodology (RSM) and four-factor-five-level central composite rotatable design (CCRD) were employed to evaluate the effects of synthesis parameters, such as reaction time (10-50 min), temperature (45-85 degrees C), lipase amount (10-30 mg/volume; 0.077-0.231 batch acidolysis units of Novo (BAUN), and pH memory (5-9), on percentage molar conversion of hexyl laurate by lipase-catalyzed direct esterification. Reaction time, temperature, and enzyme amount had significant effects on percent molar conversion. On the basis of ridge maximum analysis, the optimum synthesis conditions for hexyl laurate were a reaction time of 40.6 min, a temperature of 58.2 degrees C, an enzyme amount of 25.4 mg/volume (0.196 BAUN), and a pH memory of 5.9. The predicted percentage molar conversion of hexyl laurate was 69.7 +/- 1.4%.