Production of biocement with marine bacteria; Staphylococcus epidermidis EDH to enhance clay water retention capacity

Abstract Seven bacterial strains, isolated from marine samples beside K. pneumonia ATCC 13883 as a reference strain, were screened for urease production and calcium precipitation. Results concluded that isolate EZ15, like K. pneumonia, was urease positive. It showed high calcium precipitation (35.7%) and its biocement yield was 13 g/l. So, it was selected as a promising isolate for biocement production. It was identified biochemically and genotypically as Staphylococcus epidermidis EDH with 98% similarity. Technically, the produced biocement was observed as needle-like crystals, and the biocement aggregates mixed with calcifying S. epidermidis EDH were photographed. Data also indicated that the produced biocement, like the commercial CaCO3, successfully packed the clay particles tightly and decreased its porosity considerably, leading to increased clay water retention capacity (WRC) compared to control. Moreover, the compressive pressure resistance of the prepared biocement blocks containing S. epidermidis EDH suspension increased regularly from 267 to 362 Kg/cm2 along 28 days of solidification. The breaking load of treated blocks showed a similar trend along the same period. Advanced techniques used and characterized the produced biocement as calcium carbonate crystals (calcite).