Abstract
Acting as a “green” manufacturing route, the enzyme toolbox made up of galactose oxidase, catalase, and horseradish peroxidase can achieve a satisfactory yield of 2,5-diformylfuran derived from 30 mM hydroxymethylfurfural. However, as the concentration of hydroxymethylfurfural increases, the substrate causes oxidative damage to the activity of the tri-enzyme system, and the accumulated hydrogen peroxide produced by galactose oxidase causes tri-enzyme inactivation. The cost of tri-enzymes is also very high. These problems prevent the utilization of this enzyme toolbox in practice. To address this, galactose oxidase, catalase, and horseradish peroxidase were co-immobilized into Cu3(PO4)2 nanoflowers in this study. The resulting co-immobilized tri-enzymes possessed better tolerance towards the oxidative damage caused by hydroxymethylfurfural at high concentrations, as compared to free tri-enzymes. Moreover, the 2,5-diformylfuran yield of co-immobilized tri-enzymes (95.7 ± 2.7%) was 1.06 times higher than that of separately immobilized enzymes (90.4 ± 1.9%). This result could be attributed to the boosted protective effect provided by catalase to the activity of galactose oxidase, owing to the physical proximity between them on the same support. After 30 recycles, co-immobilized tri-enzymes still achieves 86% of the initial yield. Moreover, co-immobilized tri-enzymes show enhanced thermal stability compared with free tri-enzymes. This work paves the way for the production of 2,5-diformylfuran from hydroxymethylfurfural via co-immobilized tri-enzymes.
Highlights
It is well known that hydroxymethylfurfural (HMF) is formed by the dehydration of C6 sugars produced from lignocellulosic biomass [1,2]
Galactose oxidase from Dactylium dendroides (500–1500 U/mg protein, one unit generates a ∆A425 of 1.0 per minute at pH 6.0 at 25 ◦ C in a peroxidase and o-tolidine system), catalase from bovine liver (2000–5000 U/mg protein, one unit decomposes to 1.0 micromole of hydrogen peroxide per minute at pH 7.0 at 25 ◦ C), horseradish peroxidase (>200 U/mg protein, one unit offers 1.0 mg purpurogallin from pyrogallolin after 20 sec at pH 6.0 at 20 ◦ C), HMF, KBr, bovine serum albumin (BSA), choline chloride, and glycerol were obtained from Sigma-Aldrich Chemical Co
Cu3 (PO4 )2 nanoflowers to resist the oxidative damage aroused by the hydroxymethylfurfural substrate at a high concentration
Summary
It is well known that hydroxymethylfurfural (HMF) is formed by the dehydration of C6 sugars produced from lignocellulosic biomass [1,2]. As an important oxidized derivative of HMF, 2,5-diformylfuran (DFF) has been used as the starting material for synthesizing a host of new products, such as antifungal agents [4], pharmaceuticals [5], macrocyclic ligands [6], metal-organic compounds [7], furan-containing polymers [8,9], and cross-linking agents for poly(vinyl alcohol) [10,11], the selective oxidation of HMF to DFF has received increased attention recently [12]. A variety of chemical oxidants have been employed for the synthesis of DFF from HMF. An oxidation reaction of HMF to DFF driven by Mn (III)–salen catalysts provides DFF at an 89% yield in pH 11.3 buffered medium at room temperature [14]. The maximum observed yield of DFF is 57% with Co/Mn/Zr/Br as a catalyst
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