Enzyme-Mediated Precipitation of Heavy Metals Using Urease Extracted from Sporosarcina pasteurii

Heavy metal (HMs) pollution is a global concern that demands sustainable remediation approaches. Urease-induced carbonate precipitation provides an eco-friendly alternative that avoids dependence on live microbial systems.

This study evaluated urease extracted from Sporosarcina pasteurii for its ability to precipitate Pb²⁺ and Cd²⁺. A novel objective was to investigate whether pre-incubating urease with urea prior to heavy-metal exposure could enhance carbonate production and protect enzymatic activity.

Urease was extracted after 20 h growth. Optimal enzymatic conditions, kinetic parameters, and precipitation efficiency were assessed under varying conditions. The effect of pre-incubation was evaluated, and the precipitates were characterized using XRD.

The enzyme exhibited optimal activity at pH 8, 60 °C, and 0.25 M urea, with V_max 6.8 U mg^-¹ protein and K_m 89 mM. Pre-incubation increased carbonate production and reduced metal-induced inactivation. Maximum precipitation of Pb²⁺ and Cd²⁺ was achieved at a heavy metal concentration of 20 mM and a urea concentration of 250 mM, resulting in the formation of crystalline carbonates. The removal efficiencies were 82.2% for Cd²⁺ and 38.1% for Pb²⁺.

Extracted urease demonstrates selective affinity toward Cd²⁺ and Pb²⁺. Pre-incubation substantially enhances enzyme stability and precipitation efficiency, offering a cost-effective and sustainable approach for HMs remediation.