Precipitation of calcium carbonate in the presence of rhamnolipids in alginate hydrogels as a model of biomineralization

Abstract

This paper reports the effects of rhamnolipids presence in the alginate hydrogel and CO₃^2- solution, on the precipitation of CaCO₃ in the Ca²⁺ loaded alginate hydrogel. Characteristics of the formed particles are discussed. Model conditions containing alginate hydrogel and rhamnolipids were used in order to mimic the natural environment of biomineralization in biofilms. It has been shown that rhamnolipids affect the characteristics of precipitated calcium carbonate effect of using these biosurfactants depends on their concentration as well as whether they are directly present in the hydrogel matrix or the carbonate solution surrounding the hydrogel. The greatest effect compared to the control samples was found for the rhamnolipids in the form of micelles directly present in the hydrogel with the CaCl₂ cross-linked solution at concentration of 0.05 M. These conditions result in the highest increase in vaterite content, specific surface area, and pore volume. The mechanism of CaCO₃ precipitation in alginate hydrogel containing rhamnolipids has been proposed.