Manganese-modified corn silk composite mycelial pellets immobilized bioreactor for simultaneous removal of nitrate, zinc, and nickel

The non-compliant discharge of electroplating wastewater containing nitrate (NO3−-N) and heavy metals (HMs) harms aquatic ecosystems and makes it more difficult to control water pollution. This study prepared manganese-modified corn silk (Mn/CS) composite mycelial pellets (Mn-CMP) by combining Mn/CS with the fungal strain Alternaria sp. YNX. These Mn-CMP were then used as novel immobilized carriers to immobilize the strain Zoogloea sp. ZY8 to construct a dual-species immobilized bioreactor. Under optimal conditions, with influent concentrations of 20.0 mg L−1 NO3−-N, 1.0 mg L−1 Zinc(II) (Zn(II)), and 1.0 mg L−1 nickel(II) (Ni(II)), the bioreactor achieved simultaneous removal of NO3−-N at 97.50%, Zn(II) at 99.50%, and Ni(II) at 96.87%. During this process, manganese (Mn) oxides acted as electron shuttles and active sites to enhance electron transfer, while oxygen-containing functional groups promoted HMs adsorption, and bioprecipitation further facilitated HMs immobilization. Furthermore, high-throughput sequencing revealed core functional genes for nitrogen and energy metabolism, which microorganisms regulated to respond to environmental changes. This study provided a new perspective for using Mn-CMP to immobilize functional bacteria to treat industrial wastewater co-contaminated with NO3−-N and HMs.