Curvibacter sp. strain HJ-1 induces the formation of huntite

Abstract:

[Background] Whether in the nature or in experimental products, huntite is rare carbonate mineral. [Objective] Explore the cause of the unexpected discovery of the huntite during the culture experiments, on the basis of comprehensive analysis of the condition of all experiments related to huntite, to further explore the formation of the minerals. [Methods] A series of cultural experiments in the medium with Curvibacter sp. strain HJ-1 and initial Mg/Ca ratio of 5.0 were carried out for 30 days. During the incubation, cell density, pH, concentration of Ca2+ and Mg2+ in the medium were determined according to the scheduled time. Mineral type was identified by X-ray diffraction (XRD) and the morphology was observed by scanning electron microscopy (SEM). [Results] The pH value of the medium with strain HJ-1 increased, while the concentrations of Ca2+ and Mg2+ decreased gradually with incubation time. For control experiments (CK) without bacteria, the above three indicators were stable. The precipitation of huntite began to form on the 8th day and continued to the end of the experiment (30th day), while any minerals were not formed in the CK system. XRD patterns indicated that the number of crystal planes of huntite is increasing gradually. This means that the crystallinity of huntite tends to be better with incubation time. [Conclusion] The culture with Mg/Ca ratio of ≥2.0, the total concentration of calcium and magnesium ions of 0.03?0.07 mol/L, saturation index above 1.95 and presence of microorganisms is favorable for the formation of huntite.