Pycnoporus cinnabarinus glyoxal oxidases display differential catalytic efficiencies on 5-hydroxymethylfurfural and its oxidized derivatives

Marianne Daou,Saowanee Wikee,Eric Record,Françoise Duprat,Craig B Faulds,Emmanuel Bertrand,Bassem Yassine

doi:10.1186/s40694-019-0067-8

Abstract

Background5-Hydroxymethylfurfural (HMF), a major residual component of a lignocellulosic bio-refinery process, can be transformed into fundamental building blocks for green chemistry via oxidation. While chemical methods are well established, interest is also being directed into the enzymatic oxidation of HMF into the bio-plastic precursor 2,5-furandicarboxylic acid (FDCA).ResultsWe demonstrate that three glyoxal oxidases (PciGLOX) isoenzymes from the Basidiomycete fungus Pycnoporus cinnabarinus were able to oxidize HMF, with PciGLOX2 and PciGLOX3 being the most efficient. The major reaction product obtained with the three isoenzymes was 5-hydroxymethyl-2-furancarboxylic (HMFCA), a precursor in polyesters and pharmaceuticals production, and very little subsequent conversion of this compound was observed. However, small concentrations of FDCA, a substitute for terephthalic acid in the production of polyesters, were also obtained. The oxidation of HMF was significantly boosted in the presence of catalase for PciGLOX2, leading to 70% HMFCA yield. The highest conversion percentages were observed on 2,5-furandicarboxaldehyde (DFF), a minor product from the reaction of PciGLOX on HMF. To bypass HMFCA accumulation and exploit the efficiency of PciGLOX in oxidizing DFF and 5-formyl-2-furan carboxylic acid (FFCA) towards FDCA production, HMF was oxidized in a cascade reaction with an aryl alcohol oxidase (UmaAAO). After 2 h of reaction, UmaAAO completely oxidized HMF to DFF and further to FFCA, with FDCA only being detected when PciGLOX3 was added to the reaction. The maximum yield of 16% FDCA was obtained 24 h after the addition of PciGLOX3 in the presence of catalase.ConclusionsAt least two conversion pathways for HMF oxidation can be considered for PciGLOX; however, the highest selectivity was seen towards the production of the valuable polyester precursor HMFCA. The three isoenzymes showed differences in their catalytic efficiencies and substrate specificities when reacted with HMF derivatives.

Highlights

With the growing concerns about the depleting supply of fossil fuel and the global problem of climate change, the demands for sustainable substitutes for petroleum-based products are increasing
PciGLOX3 was heterologously produced in Aspergillus niger and purified
The enzyme showed a generally lower activity on the tested substrates compared to the other two PciGLOX enzymes, the specificity range for all three isoenzymes was similar except in the case of glycerol, which was only oxidized by PciGLOX2 and PciGLOX3 (Table 1)

Summary

Introduction

With the growing concerns about the depleting supply of fossil fuel and the global problem of climate change, the demands for sustainable substitutes for petroleum-based products are increasing. 75% of annual production of agro-industrial residues is in the form of carbohydrates, making this material highly exploitable [1]. Efforts are being directed for the conversion of plant carbohydrates into valuable chemicals and fuels. DFF is a stable derivative of HMF This molecule is considered important for the synthesis of pharmaceutical compounds [7], antifungal products [8], electroconductors [9] and polymeric materials [10]. Another important product from the oxidation of the aldehyde group of HMF is HMFCA

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Results

Conclusion