Feasibility of Microbial-Induced Calcite Precipitation in soils polluted by hydrocarbons

This study presents an investigation on the potential of biostimulation and bioaugmentation of Microbial-Induced Calcite Precipitation (MICP) in soils polluted by polycyclic aromatic hydrocarbons (PAH). Biostimulation of urea hydrolysis by soil autochthonous ureolytic bacteria was not detected over 62 days. Flow cytometry revealed Sproposarcina pasteurii at initial OD600 = 0.01 was able to grow in soil water extracts of increasing hydrocarbon concentration (TOC = 0.035-35 mg/L), showing no negative effects on cell membrane stability. Urease activity assays in soil water extracts inoculated with S. pasteurii (OD600 = 0.01 and 1) and soybean Glycine Max urease enzyme (1 and 100 g/L) indicated cell and enzyme urease inhibition was dependant on hydrocarbon and cell/enzyme concentrations. Glycine Max urease activity was unaffected at 100 g/L but at 1 g/L decreased with increasing hydrocarbon concentration up to 61%. S. pasteurii at OD600 = 1 readily decreased at the lowest hydrocarbon concentration (TOC = 0.35 mg/L) to an overall reduction of 31% at the highest concentration. Bioaugmentation of S. pasteurii (OD600, initial = 1) inoculated in the soil matrix successfully hydrolysed urea within 24 h. These results evidence for the first time the ability of model MICP bacteria S. pasteurii to grow and maintain relevant metabolic ureolytic activity in soils significantly polluted by PAH.