Nano–bio interfacial coupling regulates microbially induced calcium carbonate precipitation: Mechanistic insights and multi-objective optimization

Microbially induced calcium carbonate precipitation (MICP) is governed by the coupling between bacterial physiological activity and mineral nucleation; however, regulating such bio-mineral coupling remains challenging. Nanomaterials (NMs) offer reactive nano–bio interfaces that can link bacterial immobilization with heterogeneous CaCO₃ nucleation, yet their contribution to biomineralization efficiency remains mechanistically unclear. In this study, we report a nano-enabled strategy in which SnO₂ NMs serve as platforms for bacterial immobilization and heterogeneous mineral nucleation. Microscopic and elemental analyses reveal that SnO₂ NMs are preferentially immobilized on bacterial spore surfaces, forming a stable nano–bio interface without compromising cellular integrity. Biological assays demonstrate a concentration-dependent dual effect, where an optimal dosage of 150 mg/L increases spore germination from 0.68 to 0.78 and calcium precipitation activity (CPA) from 29.94% to 34.79%. At higher concentrations (≥200 mg/L), CPA decreases to 30.74% despite a substantial increase in metabolic activity (ETSA up to 42.84), indicating a decoupled and non-linear relationship between metabolic intensity and biomineralization performance. Multivariate analysis and response surface modeling showed that CPA was strongly correlated with spore germination (r = 0.91), whereas its relationship with metabolic activity was negligible (r = −0.03). Multi-objective optimization identified 150 mg/L as the concentration that produced the highest biomineralization performance. Microstructural characterization showed densely packed CaCO₃ crystals with uniform elemental distribution, consistent with enhanced crystal nucleation and growth. Overall, this study clarifies how nano–bio interfacial interactions influence bacterial activity and CaCO₃ precipitation, providing a framework for optimizing nano-assisted MICP systems.