Radiation facilitated-immobilized lipase (RaFIL) mini biocatalytic reactor based on epoxy decorated PP tubes: Rapid colorimetric estimation of pesticide Chlorpyrifos

Abstract

Polypropylene (PP) based ultracentrifuge tubes (PPt) have been internally surface functionalized with epoxy groups via ⁶⁰Co gamma radiation mediated simultaneous grafting of monomer 2,3-Epoxypropyl methacrylate (PEPMA-g-PPt). Radiation dose, monomer concentration and solvent polarity are optimized to achieve grafting yield of ∼62.0 g.m⁻². Enzyme Lipase from Candida rugosa has been immobilized inside the tubes via a simple, room temperature covalent coupling reaction (immobilization yield ∼73.3%). Immobilized and free lipase have been assayed spectrophotometrically by monitoring the hydrolysis of substrate 4-Nitrophenyl palmitate (PNPP) to Paranitrophenol (PNP) (λ_max = 400 nm). The Radiation facilitated-immobilized Lipase system (RaFIL) demonstrates an operational temperature range enhancement from 50 °C (free lipase) to 70 °C, and a broader pH tolerance window with optimum pH increasing from 7.4 (free lipase) to 8.0, and ∼20% more activity as compared to the free enzyme at pH 10.0. The system retains its activity for >10 cycles over 30 days, with attrition losses of <15% after seven cycles. RaFIL has been successfully demonstrated to detect pesticide Chlorpyrifos within a linear range of 0–500 µg.ml⁻¹ with LOD of 60.4 µg.ml⁻¹ (R²=0.975). The system has potential applications as a facile, low cost biocatalytic technique for rapid, onsite detection of harmful pesticides in affected areas.

Graphical Abstract

Keywords:

• Radiation grafting
• immobilization
• lipase
• biocatalytic reactor
• pesticide
• chlorpyrifos