Continuous biotransformation of bisphenol A and diclofenac by laccase in an enzymatic membrane reactor

A novel enzymatic membrane reactor (EMR) was explored for continuous removal of two trace organic contaminants (TrOCs) ubiquitously detected in wastewater - namely bisphenol A (BPA) and diclofenac (DCF) - by a commercially available laccase from Aspergillus oryzae. An ultrafiltration membrane prevented washout of the enzyme and allowed continuous removal of BPA and DCF (>85% and >60%, respectively) under a loading rate of 570 ± 70 µg/L d (BPA) and 480 ± 40 µg/L d (DCF). The BPA and DCF removal could be further improved to >95% and >80%, respectively, by dosing to the EMR a natural redox-mediator compound - syringaldehyde (5 µM) - believed to act as an electron shuttle between laccase and the target pollutants. Of particular interest was the significant retention of the TrOCs on the gel layer of enzyme on the membrane surface, and their subsequent biodegradation.