Brevibacillus laterosporus ZN5 Induces Different Carbonate Precipitations of Lead in Ammonification and Nitrate Assimilation Processes
Carbonate mineralization based on urea hydrolysis by bacteria has a significant implication in the remediation of heavy metals polluted environment, but a huge quantity of ammonium released due to the addition of urea may lead to non-point source pollution. In this study, a lead-resistant strain ZN5, identified as Brevibacillus laterosporus, which could induce different carbonate precipitations of Pb (II) through ammonification and nitrate assimilation processes without the addition of urea, was isolated. The maximum of pH values of bacterial fermentation suspensions were 9.07 and 9.22 during ammonification and nitrate assimilation processes, respectively. The minimum inhibitory concentrations of Pb (II) to strain ZN5 in two processes were 150 and 100 mg/L, respectively. Strain ZN5 could rapidly remove 94% and 70% of Pb (II) at an initial concentration of 15 mM through two processes, respectively. Furthermore, the induced carbonate precipitates of Pb (II) in ammonification and nitrate assimilation processes were dense spherical crystal of Pb3(CO3)2(OH)2 and loose irregular crystal of PbCO3, respectively, based on XRD and SEM-EDS. Besides, these two biominerals were relatively stable in dilute acid solution, especially the biomineral formed during nitrate assimilation process. These results showed that strain ZN5 had promising application in remediation of Pb-contaminated environment.
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