Highly efficient and selective production of FFCA from CotA-TJ102 laccase-catalyzed oxidation of 5-HMF

5-Formyl-2-furancarboxylic acid (FFCA) is increasingly important building blocks, which has promising applications in fuels, chemical intermediates, drugs, etc. However, highly selective oxidation of 5-hydroxymethylfurfural (5-HMF) to FFCA by enzyme catalysis is a new challenging problem due to the absence of specific enzymes. Recently we identified a kind of laccase (CotA-TJ102) from Bacillus subtilis TJ-102 could convert selectively 5-HMF to FFCA, and no further oxidation production (such as FDCA). The initial conditions resulted in low 5-HMF conversion ratio at 23.5% and low FFCA yield at 19.3% after 96 h, but high FFCA selectivity at 82.4%. Then the proposed mechanism in detail for the selective oxidation of HMF to FFCA by CotA-TJ102 was deduced and discussed. After optimization of reaction parameters such as pH, TEMPO concentration and temperature, FFCA could be obtained in a high yield of 98.55% with a 5-HMF conversion ratio of nearly 100% after a short reaction time of 12 h. Finally, after immobilization of CotA-TJ102 on magnetic nanoparticles, the FFCA yield remained 83.28% for 10 of recycling times based on the high FFCA selectivity (>96%), which reflected high stability and good reusability. Therefore, this enzymatic approach constitutes a promising method for the green production of FFCA.