Influence of culture media on bacterial organic acids production for sustainable indirect bioleaching of spent printed circuit boards

• Culture media affected bacterial organic acid production, altering types and yields. • Gluconic acid surpassed other produced acids, peaking at 2338.8 mg/l in one medium. • The spent printed circuit board was bioleached using the indirect leaching method. • B. megaterium metabolites from different media leached cerium at 30.3%, 23%, and 18%. . This study investigates, for the first time, how different culture media affect the production of organic acids by Bacillus megaterium . It examines the role of these metabolites in the bioleaching of rare earth elements (REEs) and other metals from spent printed circuit boards (SPCBs). This study explores the sustainable metal extraction from SPCBs, aiming to reduce the environmental impact of this secondary metal source. For this purpose, different culture media influenced the production of organic acids, siderophores, pH changes, glucose consumption, and bacterial growth. In media A, B, and C, gluconic acid was the dominant organic acid while other acids such as citric, oxalic, succinic, lactic, tartaric and malic were also produced. Some acids were absent in certain media, reflecting differences in metabolic activities in diverse culture media components. Indirect bioleaching experiments were performed at 10 g/l pulp density, 60°C, 160 rpm, and 24 h. Data revealed that REE extraction efficiencies varied across media, with Ce leaching reaching 30.3%, 23%, and 18% and Dy leaching at 6.9% and 6.5% in different media. The findings also highlight the influence of microbial metabolites on the leaching of Cu, Ag, Ni, Fe, Zn, and a wide range of metals (WRoM) from these complex waste matrixes. However, the metal leaching of all the reported metals varied across media due to differences in metabolite composition. Structural analyses assessed the effect of metabolites on the waste. This study complements our previous research and highlights the strain's metabolic capabilities beyond cyanide production. .