Feruloyl esterase (FAE)-catalyzed esterification reaction is as a potential route for the biosynthesis of feruloylated oligosaccharides as functional ingredients. Immobilization of FAE from Humicola insolens on metal chelate-epoxy supports was investigated. The study of effects of immobilization parameters using response surface methodology revealed the significance of enzyme/support ratio (3.25-29.25 mg/g support), immobilization time (14-38 h), buffer molarity (0.27-1.25 M) and pH (4.0-8.0). The interactions between enzyme-to-support ratio/buffer molarity and enzyme-to-support ratio/pH were found to be critical for the modulation of the immobilization activity yield and the retention of specific activity, respectively. Optimum conditions for FAE-immobilization on metal chelate Sepabeads® EC-EP R were identified to be 22.75 mg FAE/g support, pH of 5.0, 27.7 h and buffer molarity of 0.86 M. At these conditions, an activity yield of 82.4%, a specific activity retention of 143.4%, and an enzyme activity of 395.4 μmol/min. g support were achieved. Further incubation of the immobilized FAE at pH 10.0 improved its thermostability. Increasing the pore size of the epoxy support improved the retention of FAE hydrolytic activity and the esterifying efficiency of the immobilized biocatalyst. Optimally immobilized and stabilized FAE on metal chelate-epoxy support retained up to 92.9% of the free enzyme feruloylation efficiency to xylooligosaccharides.. 相似文献
ABSTRACTEnzymes require a certain level of water in their structures in order to maintain their natural conformation, allowing them to deliver their full functionality. Furthermore, as a modifier of the solvent, up to a certain level, water can modify the solvent properties such as polarity/polarizability as well as the solubility of the reactants and the products. In addition, depending on the type of the reaction, water can be a substrate (e.g., in hydrolysis) or a product (e.g., in esterolysis) of the enzymatic reaction, influencing the enzyme turnover in different ways. It is found that regardless of the type of reaction, the functionality of enzyme itself is maximum at an optimum level of water, beyond which the enzyme performance is declined due to the loss in enzyme stability. Furthermore, mass transfer limitations caused by pathway blockage and/or by reduced solubilities of the reactants and/or products can also affect the enzyme performance at higher water levels. Controlling water content of ingoing CO2 and substrates as well as precise management of enzyme support and salt hydrates are important strategies to adjust water level in reaction media, especially in supercritical environments. 相似文献
Preparation of o-palmitoyl alkyl lactates with methyl, ethyl, propyl, isopropyl and butyl lactates were attempted in a complex esterification reaction using lipases as catalysts. Compared to lactic acid, alkyl lactates were found to be less inhibitory in nature as they resulted in slightly better yields at shake-flask level. Of the alkyl lactates tested, butyl lactate showed better esterification. Porcine pancreas lipase gave higher yields of esters than Rhizomucor miehei lipase (Lipozyme IM20). 相似文献
Two different kinds of bioprocess, ethanol fermentation and subsequent microbial esterification, were coupled using Issatchenkia terricola IFO 0933 in an interface bioreactor. The strain produced ethyl decanoate (Et-DA) by esterification of exogenous decanoic acid (DA) with ethanol produced via fermentation. The efficiency of the new coupling system depended on the concentration of glucose in a carrier and DA in an organic phase (decane) in an agar plate interface bioreactor. Optimum glucose content and DA concentration were 4% and 29 mM, respectively. 相似文献
Alcohol induced reversal of enantioselectivity in the esterification of 2-chloropropionic acid using lipase from Candida cylindracea has been investigated. It was found that an alcohol having substituents both at the α- and the β-carbon preferentially esterified the S-acid, while a straight chain alcohol preferentially esterified the R-acid. Intermediate enantioselectivities were obtained with alcohols having substituents either at the α- or the β-carbon, but still in favor of the R-acid. An acyl binding domain composed of three subsites is proposed for this lipase; one for the hydrocarbon chain, a second for a methyl substituent and a third for an electronegative substituent. 相似文献
High- and low-methoxyl pectins were treated with pectin methylesterase (PME) and the functional properties of the resulting pectin gels were characterized. The degree of esterification of high- and low-methoxyl pectins decreased from 74.5% to 6.3% and 40.0% to 6.5%, respectively while not changing their molecular weight. Also, the addition of glucono-delta-lactone (GDL) dramatically affected the gel strength and the pH reduction by the GDL led to the increased syneresis of the pectin gels, which was also observed in the PME-treated samples. When flavor compounds were incorporated into the pectin gels, the flavor release from the gels increased with decreasing the degree of esterification due to increased hydrophilic properties. 相似文献
This work reports experimental equilibrium data for the esterification of pure oleic acid and a fatty acid mixture with ethanol, using an immobilized Candida antarctica B lipase as catalyst. Reactions are performed in a solvent-free system, containing a mixture of substrates and different amounts of distilled water. According to the initial amount of water and the extent of the reaction, one or two liquid phases are present. Therefore, when the equilibrium is achieved, the liquid–liquid and chemical reaction equilibria have to be simultaneously satisfied.
Several reports dealing with enzymatic reactions performed in two-phase systems have found that the value of the reaction equilibrium constant calculated from overall experimental concentrations varies not only with temperature but also with substrate ratio and water content. Although this approach is a valuable way to explore equilibrium shifts in biphasic systems, it is limited to ideal systems with constant partition coefficients. The aim of this work is to consider the biphasic nature of the reactive mixture through a computational procedure that simultaneously takes into account liquid–liquid and reaction equilibria. This approach enables the determination of a classical temperature-dependent thermodynamic equilibrium constant, which accurately fits experimental equilibrium conversions over a wide range of operating conditions. 相似文献