BACKGROUND To help mitigate future problems in the supply of platinum group metals (PGM) due to their scarcity and high demand, new recovery processes must be developed. Microbial processes are a great alternative for the recovery of PGM from waste since they are clean and environmentally friendly techniques. This research studied the microbial reduction of Pt(II) using an anaerobic granular sludge under different physiological conditions. RESULTS The anaerobic granular sludge was able to reduce Pt(II) to Pt(0) nanoparticles that were deposited intracellularly as well as extracellularly as confirmed by X-ray diffraction (XRD) and transmission electron microscopy (TEM) analyses. Hydrogen (H-2) and formate supported the chemical reduction of Pt(II) while ethanol supported the biologically catalyzed reduction of Pt(II). Increasing initial concentrations of Pt(II), ethanol or biomass were each shown to increase the Pt(II) reduction rates. CONCLUSIONS This study reported for the first time the reduction of Pt(II) using anaerobic granular sludge and provided insights that could help develop biorecovery techniques to alleviate future problems in the supply of PGMs. (c) 2018 Society of Chemical Industry