Next-generation nano-biocatalysts: extremozyme-based nanoparticle system for cypermethrin bioremediation

Extremozymes, with their exceptional catalytic activity and stability under extreme environmental conditions, have great potential for pesticide remediation. This study involves the isolation and screening of a new extremozyme-producing microbe, Proteus mirabilis JB1, for the production of alkaline-pH-stable laccase. A primary OFAT screening tested a broad range of carbon sources (glucose, lactose, xylose, sucrose, starch, glycerol, cellulose, trisodium citrate, sodium acetate), nitrogen sources (ammonium sulfate, sodium nitrate, urea, beef extract, peptone, casein, gelatin), salts (0.1 mM and 0.01 mM) such as CuSO₄, KCl, ZnCl₂, MgCl₂, MnCl₂, NiCl₂, NaCl, and CaCl₂, and pH levels (7-10). The highest enzyme activity of 0.999 U/ml was achieved using 0.25% (w/v) cellulose, 0.8% (w/v) urea, 0.1 mM MnCl₂, MgSO₄, CaCl₂, NaCl, and KCl, and 0.01 mM CuSO₄, FeSO₄, and NiCl₂ at pH 9 with good stability to surfactants (Tween 80, SDS), organic solvents (acetone, ethanol, methanol), and inhibitors (EDTA). PBD and CCD were then implemented to screen and optimize critical parameters-cellulose (1.5% w/v), urea (0.7% w/v), and MgSO₄ (0.05 mM)-to achieve an efficient increase in enzyme activity to 2.3 U/mL, demonstrating the strength and efficacy of the optimization process. Biogenic selenium nanoparticles (Bio-SeNPs) were fabricated and exhibited very high efficiency in pesticide degradation, achieving 100% degradation of cypermethrin without forming any toxic intermediates within 72 h. This research has provided a comprehensive and replicable technique covering microbial isolation, enzyme optimization, fabrication of a nanobiocatalyst, and its application. KEY POINTS: • A novel isolate, Proteus mirabilis, was employed for the production of the extremozyme laccase. • Optimization increased the yield by 9.58-fold. • Bio-SeNPs were employed to degrade cypermethrin, achieving 100% detoxification within 72 h.