New insights into the role of pH and aeration in the bacterial production of calcium carbonate (CaCO3)

Over recent years, the implementation of microbially produced calcium carbonate (CaCO 3 ) in different industrial and environmental applications has become an alternative for conventional approaches to induce CaCO 3 precipitation. However, there are many factors affecting the biomineralization of CaCO 3 , which may restrict its application. In this study, we investigated the effects of pH and aeration as the main two influential parameters on bacterial precipitation of CaCO 3 . The results showed that the aeration had a significant effect on bacterial growth and its rise from 0.5 to 4.5 SLPM could produce 4.2 times higher CaCO 3 precipitation. The increase of pH to 12 resulted in 6.3-fold increase in CaCO 3 precipitation as compared to uncontrolled-pH fermentation. Morphological characterization showed that the pH is an effective parameter on CaCO 3 morphology. Calcite was found to be the predominant precipitate during aeration-controlled fermentations, while vaterite was mainly produced at lower pH (up to 10) over controlled-pH fermentations. Further increase in pH resulted in a morphological transition, and vaterite transformed to calcite at the pH ranges between 10 and 12.