Functionalized AuNP-mycelial composites as engineered living materials for sustainable mercury remediation

Abstract

Heavy metal contamination, particularly mercury (Hg²⁺), poses severe environmental and health risks even at trace levels. Current methods face challenges such as high costs, secondary pollution, and structural complexity, which limit global adaptability. This study presents a naturally templated engineered living material (ELM) using Aspergillus niger mycelia functionalized with gold nanoparticles (AuNPs) for effective mercury bioremediation. A rapid colorimetric detection system using surface-modified AuNPs, either with conventional reductant (borate), nutrient (glucose), antibiotic (cefaclor), or ionic compound (citrate), achieved a response within 5 seconds with a detection limit down to 5 μM. Biofilters generated from AuNP-bound mycelia demonstrated efficient mercury removal, reducing Hg²⁺ from 5 ppb to 0.5 ppb, outperforming conventional polyethylene filters (Pierce™ 30 μM), and meeting World Health Organization (WHO) safety standards. The material maintained consistent performance over five reuse cycles (without any structural deformation, allowing for additional use cycles), with progressive mercury desorption for potential recovery. Growth conditions (nitrogen sources, AuNP concentration, surface functionalization, and duration of growth) could be used to influence AuNP assembly, fungal physiology, and activity of the composite materials. This scalable and cost-effective approach integrates nanotechnology with fungal bioremediation, providing a sustainable, adaptable solution for heavy metal pollution control.