Exploitation of microalgae biomineralization to produce biomaterials from marble extraction leftovers

Microalgae and cyanobacteria are able to biomineralize through microbially induced calcium carbonate (CaCO3) precipitation (MICP) via the photosynthetic pathway, which involves carbon concentrating mechanisms and is favoured by the presence of extracellular polysaccharides. MICP processes are studied to produce new materials like bioconcrete and self-healing biomaterials, able to auto-repair microfractures and reduce crack formation. Currently MICP is exploited in stone monument restoration. The present work aimed to identify microalgae able to induce CaCO3 precipitation, and to optimize the step of microalgal biomass pretreatment for the realization of a novel biomaterial starting from leftovers of Carrara’s marble cave extraction, through a transdisciplinary approach including biodesign and material driven design. Two eukaryotic microalgae and eight cyanobacteria, grown in two different culture systems, were tested to quantify polysaccharide production and then screened to quantify CaCO3 precipitation induction in a Ca-enriched medium. The strains showing the most interesting results were selected to optimize, by changing incubation conditions, the step of biomass preparation prior to biomaterial components mixing. From the biomasses produced in the optimization trial, sample artifacts were obtained and tested for their mechanical properties. The screening led to the selection of three cyanobacterial strains, showing the best characteristics in terms of calcium precipitation. They then underwent process optimization. The results of this step and of the response to mechanical solicitation of the biomaterials obtained will be also presented.