Hmfca

All chemicals were of analytical grade and used without further purification. All aqueous solutions were prepared using ultrapure Milli-Q water (SG Water). KOH was purchased from Carl Roth. HMF, DFF, HMFCA, FFCA and FDCA were from Sigma-Aldrich. Pure elements (Co, As, Te) were supplied by Sigma-Aldrich, Merck, and Alfa Aesar with high purities. All high temperature steps were performed in a tubular furnace in 10 mm quartz ampules evacuated to a pressure of 4 × 10⁻² mbar. Nickel foam (99.5% purity) used as electrode material was purchased from Goodfellow.

All chemicals were of analytical grade. HMF, DFF, HMFCA, FFCA, FDCA, 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid (ABTS) and glyoxylic acid, together with the enzymes HRP and catalase were purchased from Sigma Aldrich (Lyon, France). The glyoxal oxidases from Pycnoporus cinnabarinus, PciGLOX1 and PciGLOX2, were heterologously produced in Aspergillus niger as described previously [25 (link)]. The same protocol was used to produce the third isoform, PciGLOX3, and is reported here for the first time. The aryl alcohol oxidase (AAO) from Ustilago maydis (UmaAAO) was produced as previously reported in our laboratory [36 (link)]. The sequences of PciGLOX1, PciGLOX2 and PciGLOX3 are available in GenBank under accession numbers KU215437, KU215438 and MK268804, respectively.

HMF was kindly provided by AVA Biochem. HMFCA, DFF, FDCA, p-methoxybenzyl alcohol, p-anisaldehyde (= p-methoxybenzaldehyde), catalase from bovine liver (2000–5000 U/mg), and D₂O were purchased from Sigma-Aldrich (St. Louis, MO, USA). FFCA was purchased from TCI America (Portland, OR, USA). AmplexRed^® and horseradish peroxidase (HRP) were obtained from Invitrogen (Walthem, MA, USA). H₂O₂ was purchased from Merck (Darmstadt, Hessen, Germany).