Biomineralization of Carbonates Induced by Mucilaginibacter gossypii HFF1: Significant Role of Biochemical Parameters

Although the precipitation of carbonate minerals induced by various bacteria is widely studied, the changes in the biochemical parameters, and their significant role in the biomineralization processes, still need further exploration. In this study, Mucilaginibacter gossypii HFF1 was isolated, identified, and used to induce carbonate minerals at various Mg/Ca ratios. The biochemical parameters were determined in order to explore the biomineralization mechanisms, including cell concentration, pH, ammonia, carbonic anhydrase activity, and alkaline phosphatase activity. The characteristics of extracellular minerals and intracellular inclusions were both analyzed. In addition, the amino acid composition of the extracellular polymeric substance was also tested. Results show that the biochemical parameters provide an alkaline environment for precipitation, due to the combined effect of ammonia, carbonic anhydrase, and alkaline phosphatase. Biotic minerals are characterized by preferred orientation, specific shape, and better crystalline and better thermal stability, indicating their biogenesis. Most of the amino acids in the extracellular polymeric substance are negatived charged, and facilitate the binding of magnesium and calcium ions. The particles with weak crystalline structure in the EPS prove that it acts as a nucleation site. Intracellular analyses prove the presence of the intracellular amorphous inclusions. Our results suggest that the changes in the biochemical parameters caused by bacteria are beneficial to biomineralization, and play a necessary role in its process. This offers new insight into understanding the biomineralization mechanism of the bacteria HFF1.