Chitosan and carboxymethyl chitosan mimic biomineralization and promote microbially induced calcium precipitation

This research aimed to evaluate chitosan (CTS) and carboxymethyl chitosan (CMCS) as polysaccharides that could mimic the role of bacterial extracellular polymeric substance (EPS) in the biomineralization process through bionic experiments. The introduction of COOH resulted in higher calcium precipitation efficiency of CMCS (65.07%) than CTS (55.66%). CaCO3 nucleation on the surface of CTS and CMCS was triggered through the binding of Ca2+ to NH2, OH, COOH and NHCOCH3 groups. Moreover, the experiment of polysaccharides mediated biomineralization was conducted. The maximum calcium precipitation efficiency reached 96.07% with the addition of 0.15% CMCS. Combining the characterization results, the synergetic mineralization mechanisms between polysaccharides and bacteria were proposed. Among them, bacterial metabolic by-products (alkalinity), active groups and adhesion of polysaccharides played a significant role. This work provides a reference for further understanding of the biomineralization mechanism, and gives a new insight into the intensified strategies of MICP technology.