Exploring non-ureolytic fungal biomineralisation: Strain-dependent calcium carbonate precipitation from organic calcium sources.

This study investigates a non-ureolytic approach to fungal-based Microbially Induced Calcium Carbonate Precipitation (MICP) using organic calcium sources. As prior research has mainly focused on bacterial-based MICP, this study systematically evaluates the ability of filamentous fungi to induce non-ureolytic calcium carbonate formation. Five fungal strains, i.e., Trichoderma reesei, Neurospora crassa, Penicillium chrysogenum, Fusarium oxysporum, and Pleurotus ostreatus, were assessed using calcium acetate and calcium lactate as organic calcium sources. All strains, except P. ostreatus, facilitated calcium precipitation under at least one of the tested conditions. Notably, P. chrysogenum achieved apparent precipitation efficiencies around 90%, while F. oxysporum exceeded 96% under selected acetate and lactate conditions and exhibited more consistent growth across the tested conditions. Structural characterisation confirmed that calcium carbonate deposited on and around fungal biomass, with calcite and vaterite crystals identified as the main polymorphs. These findings show that filamentous fungi can mediate non-ureolytic calcium carbonate precipitation from organic calcium sources, with clear differences in growth, pH response, calcium removal, and mineral formation among fungal species. The study provides a microbiological basis for understanding fungal-driven carbonate biomineralisation and supports further investigation of filamentous fungi under non-ureolytic MICP conditions.