Calcite and Vaterite Biosynthesis by Nitrate Dissimilating Bacteria in Carbonatogenesis Process under Aerobic and Anaerobic Conditions

Abstract

This study deals with 16S-rDNA identified bacteria, Lysinibacillus sp., Raoultella sp., and Streptomyces sp. capable of precipitating CaCO3 through nitrate reduction aerobically and anaerobically. The produced CaCO3 crystals were analyzed using XRD, EDX, FTIR, TGA and SEM. The results showed that the carbonatogenic bacteria served as nucleation sites for CaCO3 precipitation with distinct variation in polymorph and morphology; reflecting strain-specific property. Notably, the amount of precipitated CaCO3 recorded 3.27 (aerobic), 1.55 (anaerobic), 4.15 (aerobic), 3.75 (aerobic) and 1.87 (anaerobic) g/100 mL of strains Lysinibacillus sp., Streptomyces sp. and Raoultella sp., respectively, after 240 h of incubation. The study of changes in media chemistry during carbonatogenesis process revealed positive correlation between bacterial growth, nitrate reductase activity, pH, EC, Ca2+ depletion, amount of deposited CaCO3 and NO3 − consumption. Therefore, the applications of these bacterial strains, which were employed for the first time in carbonatogenesis process, are promising in the environmental, biomedical and civil engineering fields.