Lipase-catalyzed esterification of conjugated linoleic acid with <Emphasis Type="SmallCaps">l</Emphasis>-carnitine in solvent-free system and acetonitrile

Lipase-catalyzed esterification of conjugated linoleic acid (CLA) with l-carnitine in solvent-free system and acetonitrile was studied. Three lipases (Novzym 435, Amamo AY30 and Amano AYS) have been assayed as suitable biocatalysts in the reaction. It was found that Amano AY30 was the most effective biocatalyst in both solvent-free system and acetonitrile. The conversion rate varied from 8.05 to 60.9% in terms of reaction conditions such as the amount of lipase, the presence of water, the amount of molecular sieves and reaction time. The conversions of substrate in solvent-free system were higher than that in acetonitrile. When the substrates were 1 mmol CLA and 1 mmol l-carnitine, the maximum conversion (60.9%) was obtained in solvent-free system with 150 mg lipase AY30, 50% water content and 150 mg molecular sieves at the reaction time of 24 h. A novel CLA ester product was successfully isolated and characterized by ESI-MS and ¹H NMR.     

Lemon juice improves the extractability and quality characteristics of pectin from yellow passion fruit by-product as compared with commercial citric acid extractant

An environment-friendly procedure, allowing the extraction of safe pectin products with good functional properties from yellow passion fruit by-product, was developed using two natural acid extractants, namely, pure lemon juice and citric acid solvent. The results show that both of them solubilise, from cell wall material, pectins characterised by high galacturonic acid content (64–78% w/w), degree of esterification (52–73), viscosity-average molecular weight (70–95 kDa) and capable of forming gels in the presence of high soluble solids (sucrose) content and acid. However, compared to pure citric acid solvents, lemon natural juice and its concentrate isolate, under similar extraction conditions, pectins of superior quality characteristics, i.e., higher galacturonic acid content, degree of esterification, viscosity-average molecular weight and gelling power.     

Production of biodiesel from acid waste lard

The objective of the present work was: (i) to enable biodiesel production from acid waste lard; (ii) to study the esterification reaction as possible pre-treatment at different temperatures, catalyst amount and reaction times; (iii) to evaluate biodiesel quality according to EN 14214 after basic transesterification of the pre-treated fat; and (iv) to predict the impact of using such waste as raw material in mixture with soybean oil. Temperature and catalyst amount were the most important reaction conditions which mostly affected biodiesel quality, namely viscosity and purity. The selected pre-treatment conditions were 65 °C, 2.0 wt% H₂SO₄ and 5 h, which allowed obtaining a product with a viscosity of 4.81 mm² s⁻¹ and a purity of 99.6 wt%. The proposed pre-treatment was effective to enable acid wastes as single raw materials for biodiesel production with acceptable quality; however, low yields were obtained (65 wt%). Alkali transesterification of a mixture of waste lard and soybean oil resulted in a product with a purity of 99.8 wt% and a yield of 77.8 wt%, showing that blending might be an interesting alternative to recycle such wastes. Also, because in addition to using conventional and relatively economical processes, some biodiesel properties depending on the raw material composition (such as the iodine value) might even be improved.     

Anomeric selectivity in the synthesis of galloyl esters of d-glucose

The anomeric selectivity of the ester formation between d-glucopyranose and gallic acid was investigated under a variety of conditions. A new protocol was established that allows performing the reaction under conditions where mutarotation is very slow. Highly α- or β-selective transformations are possible when starting with α- or β-d-glucopyranose, respectively. Due to the kinetic anomeric effect, a high α-selectivity is more difficult to achieve than a high β-selectivity. The new methodology presented in this article was compared with established procedures for the synthesis of gallotannins. In addition to the advantages of a high yield and an easy purification protocol, the new procedure uniquely allowed for a highly selective synthesis of α-products.     

Modelling and experimental studies on lipase-catalyzed isoamyl acetate synthesis in a microreactor

A lipase-catalyzed synthesis of isoamyl acetate was studied in a continuously operated pressure-driven microreactor. The esterification of isoamyl alcohol and acetic acid occurred at the interface between n-hexane and an aqueous phase with dissolved lipase B from Candida antarctica. By adjusting flow rates of both phases, a parallel laminar flow with liquid–liquid boundary in the middle of the microchannel could be reestablished and a separation of phases was achieved at the y-shaped exit of the microreactor. Since product remained in the organic phase, this also enabled its continuous separation from the aqueous phase with the enzyme. A three-dimensional mathematical model was developed, considering the velocity profile developed for steady-state conditions between two immiscible fluids. The model contained convection, diffusion, and enzyme reaction terms, where esterification rate was described with a Ping-Pong Bi-Bi mechanism and inhibition by both substrates. Experimental data, which were in good agreement with model simulations, have demonstrated 35% conversion at residence time 36.5 s at 45 °C and at 0.5 M acetic acid and isoamyl alcohol inlet concentrations, which is much faster as in any literature reported so far. According to model simulations, obtained by non-equidistant finite differences numerical solutions of complex non-linear equations system, further microreactor design and process optimization are feasible.     

Effect of fatty acid chain length on initial reaction rates and regioselectivity of lipase-catalysed esterification of disaccharides

In a reaction medium mixture of 9:11 t-BuOH and pyridine (v/v) the effect of fatty acid chain length (C-4-C-12) on C. antarctica lipase B (Novozym 435, EC 3.1.1.3) catalysed esterification was studied. alpha and beta maltose 6'-O-acyl esters in an anomeric molar ratio of 1.0:1.1 were synthesised independently of the chain length, but the initial specific reaction rate increased with decreasing chain length of the acyl donor. The product yield followed the same trend with a lauryl ester yield of 1.1% (mol/mol) and a butyl ester yield of 27.6% (mol/mol) after 24 h of reaction. With sucrose as the acyl acceptor the 6'-O-acyl and 6-O-acyl monoesters were formed with fatty acids of chain length C-4 and C-10 while the 6',6-O-acyl diester was formed only with butanoic acid (C-4:0) as acyl donor. The 6'-O-acyl and 6-O-acyl monoesters and the 6',6-O-acyl diester of butanoic acid were produced in a molar ratio of 1.0:0.5:0.2 and with decanoic acid (C-10:0) the 6'-O-acyl and 6-O-acyl monoesters were formed in the ratio of 1.0:0.3. The highest initial reaction rate and yield were obtained with the shortest chain length of the acyl donor. Initial reaction rates and ester yields were affected by the solubility of the disaccharide, with higher reaction rates and yields with maltose than with sucrose, while no formation of esters were observed with either cellobiose or lactose as acyl acceptors.     

Whole cell catalyzed esterification of fatty acids to biodiesel using Aspergillus sp.

Abstract

Powdered biomass of Aspergillus sp. (RBD01) was used to carry out esterification of long chain fatty acids for biodiesel production. Dry biomass of Aspergillus sp. at 20% (w/w) with respect to the fatty acid was able to completely esterify oleic acid to ethyl ester at 35°C, in 36 h, with step wise addition of alcohol. Similar conditions also resulted in yield of 64.5% and 58% of ethyl ester from stearic acid and palmitic acid, respectively. However, the presence of methanol resulted in 87.5%, 71% and 41% of methyl ester from oleic, palmitic and stearic acid. Furthermore, it was found that the efficiency of biomass decreased by only 10% with its repeated use up to four cycles.     

Chemometric analysis of lipase-catalyzed synthesis of xylitol esters in a solvent-free system

Immobilized Candida antarctica lipase B-catalyzed esterification of xylitol and two fatty acids (capric and caproic acid) were studied in a solvent-free system. The Taguchi orthogonal array method based on three-level-four-variables with nine experiments was applied for the analysis and optimization of the reaction parameters including time, substrate molar ratio, amount of enzyme, and amount of molecular sieve. The obtained conversion was higher in the esterification of xylitol and capric acid with longer chain length. The optimum conditions derived via the Taguchi approach for the synthesis of xylitol caprate and xylitol caproate were reaction time, 29 and 18 h; substrate molar ratio, 0.3 and 1.0; enzyme amount, 0.20 and 0.05 g, and molecular sieve amount of 0.03 g, respectively. The good correlation between the predicted conversions (74.18% and 61.23%) and the actual values (74.05% and 60.5%) shows that the model derived from the Taguchi orthogonal array can be used for optimization and better understanding of the effect of reaction parameters on the enzymatic synthesis of xylitol esters in a solvent-free system.     

Homogeneous butyrylation and lauroylation of poplar wood in the ionic liquid 1-butyl-3-methylimidazolium chloride

Wood meal was dissolved under identical conditions in the ionic liquid 1-butyl-3-methylimidazolium chloride ([C₄mim]Cl) and homogeneously esterified with butyryl chloride and lauroyl chloride in the presence of triethylamine as a neutralizer. The effect of the molar ratio of reagent to the hydroxyl groups in wood on the properties of the esterified wood and the possible mechanism of the homogeneous esterification of wood in this reaction medium were studied. Furthermore, the physicochemical properties of the esterified wood were characterized by FTIR, solid-state CP/MAS ¹³C NMR, TGA/DTG and SEM. The results confirmed that the homogeneous modifications were successfully processed and highly substituted wood esters could be obtained by reacting the dissolved wood in this homogeneous system.     

Enzymatic synthesis of sialic acid derivative by immobilized lipase from Candida antarctica

The effects of important reaction parameters on the enhancement of sialic acid derivative lipophilic properties through the lipase-catalyzed esterification of N-acetyl neuraminic acid methyl ester are investigated in this study. It is found that the lipase Novozym 435 from Candida antarctica is particularly useful in the preparation of sialic acid methyl ester monononanoate (SAMEMN). The optimum temperature for the SAMEMN synthesis reaction using Novozym 435 is 60 °C, and nonanoic anhydride is found to be the best substrate among all acyl donors. The Novozym 435-catalyzed esterification of N-acetyl neuraminic acid methyl ester gave a maximum yield of 87.7% after 6 h in acetonitrile at 60 °C. Because the novel method developed is simple, yet effective, it could potentially be used industrially for the production of sialic acid derivatives.