Continuous enzymatic polymerization of phenol in a liquid–solid circulating fluidized bed

A liquid–solid circulating fluidized bed (LSCFB) system consisting of 3.8 cm I.D. and 4 m high riser and 12 cm I.D. and 3.5 m high down-comer was investigated in this study for the continuous polymerization of phenol. Approximately 8.5 kg immobilized particles containing soybean seed hull peroxidase enzymes were applied in the LSCFB system. The continuous enzymatic polymerization was carried out in the riser section by introducing phenol and hydrogen peroxide at the entrance of the riser. Under optimized hydrodynamic conditions and by keeping the molar concentration ratio of phenol to H2O2 of 1:2, 54% conversion of phenol was achieved. The down-comer of the LSCFB was utilized for the regeneration of the coated immobilized enzyme particles. The effect of the superficial liquid velocity and an initial substrate concentration was studied. Our experimental results show that an enzymatic reaction and the regeneration of the biocatalysts can be carried out simultaneously and independently in the LSCFB system. Furthermore, this work opens the possibilities for many bioprocesses where the deactivation of the biocatalysts is a major problem and the regeneration of the biocatalysts is required.