Preparation of stable cross-linked enzyme aggregates (CLEAs) of NADH-dependent nitrate reductase and its use for silver nanoparticle synthesis from silver nitrate
•Immobilization of NADH-dependent nitrate reductase as CLEAs from cell extract•Effect of precipitant and cross-linking on enzyme activity recovery was studied.•Immobilization as CLEAs enhanced thermal stability of enzyme•Synthesis of silver nanoparticles of size 10–20 nm was demonstrated using CLEAs.•Reusability of CLEAs during silver nanoparticle synthesis was determined.
The NADH-dependent nitrate reductase from Fusarium oxysporum cell extract was directly immobilized as cross linked enzyme aggregates (CLEAs) and investigated for the synthesis of silver nanoparticles by a reduction of silver nitrate. The effects of precipitant type and cross-linking on activity recovery of enzyme in CLEAs were studied. After aggregation of enzyme with ammonium sulfate followed by cross-linking formed aggregates for 4 h with 8 mM glutaraldehyde, 93% activity recovery was achieved in CLEAs with enhanced thermal stability at 50 °C and 40 °C. Scanning electron microscopy analysis showed that immobilized NADH-dependent nitrate reductase was of spherical structure. CLEAs showed 90% catalytic yield even after 4 cycles of repeated use in silver nanoparticle synthesis at pH 7.2 and temperature 35 °C.
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Journal: Catalysis Communications - Volume 53, 5 August 2014, Pages 62–66