Enzymatic Polymerization of Dihydroquercetin (Taxifolin) in Betaine-Based Deep Eutectic Solvent and Product Characterization

Maria Khlupova,Alexander Yaropolov,Alla Shestakova,Vyacheslav Chertkov,Irina Vasil’Eva,Olga Morozova,Galina Shumakovich,Elena Zaitseva

doi:10.3390/catal11050639

Maria Khlupova, Alexander Yaropolov + Show 6 more

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https://doi.org/10.3390/catal11050639

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Abstract

Deep eutectic solvents (DESs) are an alternative to conventional organic solvents in various biocatalytic reactions. Meanwhile, there have been few studies reporting on synthetic reactions in DESs or DES-containing mixtures involving oxidoreductases. In this work, we have studied the effects of several DESs based on betaine as the acceptor of hydrogen bonds on the catalytic activity and stability of laccase from the basidial fungus Trametes hirsuta and performed enzymatic polymerization of the flavonoid dihydroquercetin (DHQ, taxifolin) in a DES–buffer mixture containing 60 vol.% of betaine-glycerol DES (molar ratio 1:2). The use of the laccase redox mediator TEMPO enabled an increased yield of DHQ oligomers (oligoDHQ), with a number average molecular weight of 1800 g mol−1 and a polydispersity index of 1.09. The structure of the synthesized product was studied using different physicochemical methods. NMR spectroscopy showed that oligoDHQ had a linear structure with an average chain length of 6 monomers. A scheme for enzymatic polymerization of DHQ in a DES–buffer mixture was also proposed.

Highlights

We have evaluated the effects of betaine-based Deep eutectic solvents (DESs) and DES–buffer mixtures on the activity and stability of the fungal laccase Trametes hirsuta; we have performed biocatalytical polymerization of DHQ in a DES–buffer mixture using the laccase–mediator system and characterized the resulting product using various physicochemical methods
When using DESs as a medium for enzymatic reactions, it is necessary to take into account their effects on the activity and stability of the enzyme
DESs based on betaine as an acceptor of hydrogen bonds and various donors of hydrogen bonds were used in the work

Summary

Introduction

Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. The use of traditional organic solvents is often limited by their toxicity, explosiveness, and negative impacts on the environment. There has been a much greater focus on non-toxic, non-volatile, biodegradable, and environmentally friendly solvents to be used in chemical and biological reactions. In the 1990s, research on the replacement of traditional organic solvents was mainly focused on the use of various ionic liquids (ILs) [1,2,3]. The complexity of synthesis, high cost, and toxicity of ILs significantly limit their use in industry [2,4]

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