Three-Phasic Flow Bioreactor for Obtaining 5-Formyl-2-Furancarboxylic Acid Catalyzed by an Immobilized Laccase Using Copper Sulfate as a Stabilizing Agent.

The effect of CuSO4 on the stability of an immobilized laccase during the oxidation of HMF to FFCA was determined in a batch bioreactor and in a triphasic flow bioreactor. The enzyme was immobilized on a support functionalized with an epoxide and glyoxyl group; the latter achieved the highest immobilization yield by activity (87.5%). In batch oxidation of HMF catalyzed by laccase immobilized on a support with glyoxyl groups reached the highest conversion percentages (100%). In the biocatalyst stability, the addition of 20 mM CuSO4 allowed achieving 50% HMF conversion at the end of the third cycle. In the absence of CuSO4, the biocatalyst was unable to catalyze the reaction. The oxidation in packed-bed flow bioreactor resulted in the production of FFCA only. With CuSO4, the stability of the biocatalyst was maintained for 48 h, with a FFCA yield of 95%. The UM values (0.2-5 cm/min) demonstrated that above an air flow rate of 0.1 mL/min, there are no mass transfer problems affecting the reaction yield. The space-time yield of FFCA (STY FFCA) (1.54 (mM/min)) was higher for the continuous system in the presence of CuSO4. Overall, this system provides a promising and scalable platform for sustainable industrial biocatalysis.