Decolorization of dye solutions by tyrosinase in enzymatic membrane reactors

BACKGROUND The main aim of this study was to investigate the decolorization performance of enzymatic membrane reactors (EMRs) using tyrosinase, including direct contact membrane reactor (DCMR) and immobilized enzyme membrane reactor (IEMR). The crosslinked polyacrylonitrile (PAN)/chitosan composite membrane was employed in a separation unit as support for tyrosinase immobilization to decolorize two common Acid Blue 113 (AB113) and Direct Black 22 (DB22) azo dyes for the first time. RESULTS According to the obtained results, the optimum enzyme amount, which could be immobilized on the membrane surface, was 25 units. The proper operating conditions for both DCMR and IEMR were determined as pH 6.5 and temperature 30 degrees C. Both the reactors initially accounted for around 96% and 94% decolorization for AB113 and DB22, respectively. To determine the reusability of EMRs after 10 cycles, 83.1% and 78.5% dye removal were achieved using IEMR for AB133 and DB22, respectively; while for DCMR, this amount reduced to 60.5% and 58.3% for AB113 and DB22, respectively. CONCLUSION The proposed IEMR maintained a high dye removal amount through the studied pH and temperature ranges. However, the performance of DCMR considerably reduced under the intensive operating conditions as well as in the long-term operation. As a result, the suggested immobilized enzyme showed superior and stable performance compared to the free one in the long-term operation. (c) 2019 Society of Chemical Industry