Enterobacter sp. biofilm at the air-water interface promotes carbonate precipitation

Abstract

Biofilm capable of carbonate mineralization can create supersaturated carbonate microenvironment around it. However, the contribution of biofilms in microbially-induced carbonate precipitation is still unclear. In this study, ammonification-driven carbonate precipitation of Enterobacter sp. generated biofilm at the gas-liquid interface of the medium during standing culture, and a mechanical method was applied to destroy biofilms, and the effect of biofilm composed of Enterobacter sp. at the air-water interface on the formation of carbonate were investigated by comparing whether biofilm was disrupted or not. It was found that biofilm destruction inhibited carbonate formation, which was reflected in the delay of the occurrence of mineral formation time point from day 4 to day 6 during the 10-day mineralization experiment, meanwhile, the mineral mass decreased by about 50% compared with the biofilm was not destroyed at day 10. The phenomenon of mineral formation around biofilm suggested that biofilms was more suitable for the formation of carbonate minerals. Those pieces of evidence indicated that the Enterobacter sp. biofilm at the gas-liquid interface accelerated carbonate precipitation. In addition, a particular form of concave spherical calcite was found only around biofilms. This result has value for the interpretation of the morphology of carbonate induced by microorganisms.