Bioprospecting Ureolytic Rock Bacteria for Calcium Carbonate Precipitation Inducer

Abstract

The application of calcium carbonate precipitation-inducing bacteria in the past two decades has become an alternative in green technology development, particularly in construction as self healing agent of concrete and in the waste treatment as contaminants remover (e.g., radioactive pollutants and heavy metals). This study aimed to obtain potential bacterial isolates from rock samples that can induce calcium carbonate precipitation and characterize the precipitate produced. This study began with the isolation of bacteria from rock samples taken from an arid area (Malaka, East Nusa Tenggara) using Nutrient Broth-urea-CaCl2 media. Colonies showing the formation of calcium carbonate precipitation were then purified and selected for the ureolytic activity assay using Christensen's urea agar. Bacterial isolates with high ureolytic activity were selected for further characterization of their ability to produce calcium carbonate precipitation. Five bacterial isolates with the best precipitation ability were obtained. Each isolate had a different ability to induce calcium carbonate precipitation, and the resulting crystal morphology was also different. Isolate M 2.6 was the best bacterial isolate capable of inducing the highest calcium carbonate precipitation, which was 2.6 g/L. This isolate was later identified as Mesobacillus campisalis. The calcium carbonate precipitate produced by the five selected isolates ranged from 1.4 g/L to 2.6 g/L. The Field Emission Scanning Electron Microscopy (FESEM)-Energy Dispersive Spectroscopy (EDS) characterization revealed that the precipitate resulting from the bacterial isolates was calcium carbonate. This was indicated by the mass percent value, which was dominated by three main elements, namely O, Ca, and C, with a mass ratio of approximately matching CaCO3.