Surfactin as a Green Agent Controlling the Growth of Porous Calcite Microstructures

Abstract

This study presents a new, simple way to obtain mesoporous calcite structures via a green method using an eco-friendly surface-active compound, surfactin, as a controlling agent. The effects of synthesis time and surfactin concentration were investigated. The obtained structures were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC) coupled with gas mass spectrometry (QMS) analysis. The experimental data showed that surfactin molecules significantly changed the morphology of the calcite crystals, roughening and deforming the surface and creating a greater specific surface area, even at low biosurfactant concentrations (10 ppm). The size of the crystals was reduced, and the zeta potential value of calcium carbonate was more negative when more biosurfactant was added. The XRD data revealed that the biomolecules were incorporated into the crystals and slowed the transformation of vaterite into calcite. It has been shown that as long as vaterite is present in the medium, the calcite surface will be less deformed. The strong influence of surfactin molecules on the crystal growth of calcium carbonate was due to the interaction of surfactin molecules with free calcium ions in the solution as well as the biomolecules adsorption at the formed crystal surface. The role of micelles in crystal growth was examined, and the mechanism of mesoporous calcium carbonate formation was presented.

Searching for microbial contribution to micritization of shallow marine sediments

“…These problems could be addressed using omics technologies (metagenomics, metatranscriptomics, metaproteomics and metabolomics) to unravel new microbial taxa and metabolisms (Strous et al, 2012). For example, bacterial biosurfactants have been recently shown to promote calcium carbonate precipitation in pure culture (Bastrzyk et al, 2019; Bastrzyk et al, 2020; Stroescu et al, 2012), and metagenomic investigations could be used to assess the presence of genes encoding for such compounds, and their potential impact in micritized sediments. New functions affecting the H + /HCO 3 − balance in shallow marine sediments could be discovered in already‐known phyla.…”