Biomimetic Regulation of Microbially Induced Calcium Carbonate Precipitation Involving Immobilization of Sporasarcina pasteurii by Sodium Alginate

Many researchers in the past decade have explored the controlled synthesis of calcium carbonate with specific size, morphology, and polymorphism. This study explored the biomimetic regulation of microbially induced calcium carbonate precipitation (MICP) via employing immobilization technology. Calcium alginate gel was used to immobilize Sporosarcina pasteurii, a urea-positive microorganism. CO32- was generated driven by ureolysis and reacted directly with Ca2+ that was cross-linked in sodium alginate to produce CaCO3 precipitation. Based on SEM, TEM, XRD, HRTEM, and SAED results, amorphous calcium carbonate, vaterite, and calcite appeared in order. This evolution of CaCO3 morphology and polymorphism apparently conforms to Ostwald's rule. Various concentrations (1-3%) of sodium alginate caused different alginate molecules to form due to the collapse of calcium alginate gel carrying negative charges and exerting a significant influence on the morphology of CaCO3 from hexagonal vaterite to capsule-shaped vaterite. The techniques discussed here can also be applied to other polysaccharides on CaCO3, which implies that they are valuable with regard to polymorphic regulation because abundant polysaccharide apparently favors the vaterite polymorph.