Recombinant Organophosphorus Acid Anhydrolase and Silver Nanoparticles Immobilized Electrospun Nanofibers for Biocatalysis and Antimicrobial Functions

Abstract

Organophosphate compounds (OPs) are widely used pesticides among all existing pesticide categories, yet their toxicity and persistence pose significant environmental and health challenges. Nearly one-third of global pesticide poisoning cases occur in a single country, highlighting the urgent need for effective remediation. Although enzyme-based remediation is sustainable, its effectiveness is impeded by the limited recyclability and inherent instability of the free enzymes. The present research describes recombinant organophosphorus acid anhydrolase-FL variant (OPAA-FL) enzyme-conjugated polyvinyl alcohol (OPAA-PVA) nanofiber and silver nanoparticle-embedded-PVA (Ag-PVA) nanofiber-mediated biocatalytic hydrolysis of ethyl paraoxon (EP) to p-nitrophenol (PNP) and subsequently its reduction into p-aminophenol (PAP). The recombinant OPAA-FL enzyme was expressed in E. coli, purified, and subsequently immobilized onto an electrospun PVA nanofiber mat. In parallel, silver nanoparticle (AgNP)-embedded PVA (Ag-PVA) nanofibers were synthesized in situ through the reduction of AgNO3 in PVA solution upon dissolving at 80 °C. The OPAA-PVA nanofiber achieved 91.2% degradation of 350 μM EP within 30 min using a UV spectrophotometer, yielding PNP as the primary product. Consequently, the Ag-PVA nanofiber facilitated the NaBH4-assisted reduction of PNP to PAP. Additionally, Ag-PVA nanofibers exhibit an antimicrobial activity against bacteria. Overall, the integrated OPAA-PVA and Ag-PVA nanofiber system demonstrates an enhanced, sequential, and recyclable biocatalytic−nanocatalytic process for rapid degradation of EP to PNP with reduction of PNP to PAP along with antimicrobial properties, highlighting its strong potential for sustainable water bioremediation applications.