Bioremediation of organophosphorus compounds using highly stable packed bed microreactor developed with OPH (organophosphorus hydrolase) coated nanofiber

Cellulose nanofibers (CNF) provide a large surface area for enzyme immobilization and facilitate easy recovery from solution, enabling repeated use. The crosslinked coating of organophosphorus hydrolase (OPH) on these nanofibers significantly enhanced enzyme stability compared to the free form. Among the tested systems, diethylaminoethyl cellulose/magnetic particle-OPH (DEAE/MP-OPH) exhibited the highest activity retention, maintaining approximately 90% of its initial activity after 30 days. Similarly, carboxymethyl cellulose/margnetic nanopaticle-OPH (CMC/MP-OPH) and cellulose nanofiber-OPH (CNF-OPH) showed improved stability over free OPH, retaining 78% and 70% of their initial activities, respectively, at the end of the reaction period.These OPH-coated nanofibers played a crucial role in the bioremediation of paraoxon, a highly toxic organophosphorus compound. When used in a packed bed reactor (PBR) integrated with CNF-OPH, the system achieved a bioremediation rate of 0.081 mM/min (compared to 0.0084 mM/min in a continuous stirred-tank reactor, CSTR). The degradation rate using the PBR was 9.6 times higher than that with the CSTR. With a residence time of only 4 min, the PBR achieved complete removal (100%) of paraoxon from the solution. The enhanced stability in the PBR arises from the absence of mechanical agitation and a uniform flow regime that minimizes physical stress on the immobilized enzyme. The integration of immobilized OPH with PBR operation provides a highly efficient, stable, and scalable platform for the continuous remediation of organophosphate pollutants.