Co-Precipitation of Cd, Cr, Pb, Zn, and Carbonates Using Vibrio harveyi Strain Isolated from Mediterranean Sea Sediment

Heavy metal contamination is listed among the most alarming threats to the environment and human health. The detrimental effects of heavy metals in the natural environment span from a reduction of biodiversity to toxic effects on marine life—through microplastic born heavy metals, to impairment of microbial activity in the soil, and to detrimental effects on animal reproduction. A host of different chemical and biological technologies have been proposed to alleviate environmental contamination by heavy metals. Relatively less attention has been paid to the microbial precipitation of heavy metals, as a side mechanism of the most general process of microbially induced calcite precipitation (MICP). This process is currently receiving a great deal of interest from both a theoretical and practical standpoint, because of its possible practical applications in concrete healing and soil consolidation, and its importance in the more general framework of microbial induced mineral precipitation. In this study, we analyse the ability of the marine bacteria Vibrio harveyi in co-precipitating CaCO3 minerals, together with Cd, Cr, Pb, and Zn added in form of nitrates, from solutions containing CaCl2. The precipitated carbonatic minerals were a function of the different heavy metals present in the solution. The process of co-precipitation appears to be rather effective and fast, as the concentrations of the 4 heavy metals were reduced in 2 days by 97.2%, on average, in the solutions. This bioremediation technology could be used as environmental friendly procedure to de-contaminate suitable environmental matrices. The high performance of this process makes it particularly interesting for an upscaling from lab to field.