Ultrasound-Assisted Esterification of Valeric Acid to Alkyl Valerates Promoted by Biosilicified Lipases

Abstract

A novel, environmentally friendly, and sustainable ultrasound-assisted methodology in the valorization of valeric acid to alkyl valerate using a biosilicified lipase from Candida antarctica is reported. This one-pot room temperature methodology of enzyme biosilicification leads to biosilicified lipases with improved activity and reaction efficiency as compared to free enzymes. Yields in the ultrasound-promoted esterification of valeric acid was ca. 90% in 2 h with 15% m/v of biosilicified lipase (Bio-lipase; 616 U/g biocatalyst enzymatic activity) and a molar ratio 1:2 (valeric acid:ethanol), slightly superior to that observed by the free enzyme (75% conversion, 583U/g biocatalyst enzymatic activity). The reuse of enzymes in these conditions was tested and the results show a relatively good reusability of these biosilicified enzymes under the investigated conditions, particularly preserving fairly stable specific activities (616 vs. 430 U/g biocatalyst after four reuses).

Sol-Gel Immobilisation of Lipases: Towards Active and Stable Biocatalysts for the Esterification of Valeric Acid

“…Despite these protein losses, the biocatalyst still retained significant amounts of lipase, remaining highly active during the investigated esterification reactions. These relevant results further supported the high stability of the immobilised enzymes compared with the free enzyme, particularly under the investigated conditions [ 20 ].…”

“…The hydrolytic free and immobilized enzyme, Candida antarctica lipase B (CalB), was employed in order to study the efficiency of the encapsulation or biosilicification procedure, conducted by CH and MW methodologies. The immobilized lipase was previously characterized by our group using different techniques such as Brunauer-Emmett-Teller surface area analysis (BET), thermogravimetric analysis (TGA) and X-Ray Photoelectron Spectroscopy (XPS) [ 20 ]. The reported results indicated that the biocatalyst started being a non-porous material, becoming highly porous after successive reuses due to the progressive loss of organic compounds.…”

“…Considering this, the aim of the present work was to optimize the catalytic esterification of valeric acid to ethyl valerate (marketed as green apple flavour) by using sol-gel biosilicified enzymes and comparing the performance of two different methodologies: conventional heating and MW-assisted processes. Moreover, different experiments with metal containing biocatalysts were carried out in order to improve their recovery and subsequent reuse [ 20 ].…”

Substrate-Specificity ofCandida rugosaLipase and Its Industrial Application

“…A recent novel approach based on lipase encapsulation by using biomimetic silica mineralization (the so-called biosilicification) was proved to offer the possibility to render active and stable biocatalysts entrapped within a silica support. − A lot of experiments are executed with Candida Antarctica lipase. One example shows that gel-entrapped CRL lipase was prepared by polycondensation of hydrolyzed tetramethoxysilane and isobutyltrimethoxysilane but certain modifications were introduced into the conventional immobilization procedure.…”

NH4F Modified Al-SBA-15 Materials for Esterification of Valeric Acid to Alkyl Valerates

“…To overcome the previously mentioned problems, heterogeneous catalysts were designed and employed in esterification reactions for the production of biofuels, including sulfonic resins [7], zeolites [8], and others based on zirconium oxide [9] and niobic acid [10]. Alternatively, this esterification reaction can be performed enzymatically under mild conditions [11,12].…”