Table 2.
Oxidation of HMF, DFF, HMFA and FFA with different enzymes after 72 h
| Yield [%] | Enzyme | No enzyme | |||||
|---|---|---|---|---|---|---|---|
| AO | GAO | CAT | LAC | LPO | HRP | ||
| Substrate: HMF | |||||||
| HMF | 71.2 | 94.9 | 100 | 100 | 99.4 | 99.3 | 99.7 |
| DFF | 25.6 | 5.1 | – | – | – | – | 0.3 |
| HMFA | – | – | – | – | 0.6 | 0.7 | – |
| FFA | 3.1 | – | – | – | – | – | – |
| FDCA | – | – | – | – | – | – | – |
| Substrate: DFF | |||||||
| HMF | 0.4 | 2.1 | 0.7 | 0.7 | 0.7 | 0.7 | 0.5 |
| DFF | 96.4 | 96.6 | 98.2 | 98.0 | 98.2 | 98.4 | 98.5 |
| HMFA | – | – | – | – | – | – | – |
| FFA | 3.2 | 1.3 | 1.1 | 1.3 | 1.1 | 0.9 | 1 |
| FDCA | – | – | – | – | – | – | – |
| Substrate: HMFA | |||||||
| HMF | – | – | – | – | – | – | 100 |
| DFF | – | – | – | – | – | – | – |
| HMFA | 100 | 97.1 | 100 | 99.9 | 96.4 | 95.4 | – |
| FFA | – | 2.7 | – | – | 0.4 | 0.6 | – |
| FDCA | – | 0.2 | – | 0.1 | 3.1 | 4.0 | – |
| Substrate: FFA | |||||||
| HMF | – | – | – | – | – | – | – |
| DFF | – | – | – | – | – | – | – |
| HMFA | 18.2 | – | 0.3 | 0.2 | 0.9 | – | – |
| FFA | 70.2 | 99.4 | 99.1 | 98.6 | 95.9 | 99.3 | 99.5 |
| FDCA | 11.6 | 0.6 | 0.6 | 1.1 | 3.2 | 0.7 | 0.5 |
Reaction conditions: final reaction volume 5 mL, 1, 2 or 8 µM enzyme (1 µM AO, 2 µM CAT and 8 µM GAO, LAC, LPO and HRP) or no enzyme (control), 10 mM HMF, DFF, HMFA or FFA in 50 mM sodium phosphate buffer (pH 7) at 30 °C and constant stirring at 150 min−1. Reactions with AO also included 1 µM FAD. HMF 5-hydroxymethilfurfural, HMFA 5-hydroxymethyl-2-furoic acid, DFF 2,5-diformylfuran, FFA 5-formyl-2-furoic acid, FDCA 2,5-furandicarboxylic acid, AO alcohol oxidase from Pichia pastoris, GAO galactose oxidase from Dactylium dendroides, CAT catalase Aspergillus niger, LAC laccase from Trametes versicolor, LPO fungal lignin peroxidase, HRP horseradish peroxidase. The average relative error was ± 11% and was estimated based on selected repeated experiments