Extracellular polymeric substance of Rhodococcus opacus bacteria effects on calcium carbonate formation

An extracellular substance extracted from the bacterial strain Rhodococcus opacus was used as a template for calcium carbonate precipitation from CaCl2 and Na2CO3 solutions at 25 and 37 °C. Obtained crystals were characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD) and Raman spectroscopy. Kinetics of precipitation was investigated by conductivity measurements. The obtained results show that the used biopolymer does not affect the crystal structure but acts as a nucleation centers leading to the formation of calcite crystals with the regular size. This effect is concentration dependent i.e. the EPS concentration increase causes the crystal size decreases, and is greater if calcium chloride solution if mixed with EPS 15 min before the addition of sodium carbonate solution. The temperature increase strengthens this effect