Effect of (in)organic additives on microbially induced calcium carbonate precipitation

Aim
This study aimed to understand the morphological effects of (in)organic additives on microbially induced calcium carbonate precipitation (MICP).

Methods and results
MICP was monitored in real-time in the presence of (in)organic additives: bovine serum albumin (BSA), biofilm surface layer protein A (BslA), magnesium chloride (MgCl2) and poly-L-lysine. This monitoring was carried out using confocal microscopy to observe the formation of CaCO3 from the point of nucleation, in comparison to conditions without additives. Complementary methodologies, namely scanning electron microscopy, energy-dispersive X-ray spectroscopy and X-ray diffraction, were employed to assess the visual morphology, elemental composition, and crystalline structures of CaCO3, respectively, following the crystals’ formation. The results demonstrated that in the presence of additives, more CaCO3 crystals were produced at 100 minutes compared to the reaction without additives. The inclusion of BslA resulted in larger crystals than reactions containing other additives, including MgCl2. BSA induced a significant number of crystals from the early stages of the reaction (20 minutes) but did not have a substantial impact on crystal size compared to conditions without additives. All additives led to a higher content of calcite compared to vaterite after a 24-hour reaction, with the exception of MgCl2, which produced a substantial quantity of magnesium calcite.

Conclusions
The work demonstrates the effect of several (in)organic additives on MICP and sets the stage for further research to understand additive effects on MICP to achieve controlled CaCO3 precipitation.