Abstract

Bacterial chemical reactions, such as urea hydrolysis can induce calcium carbonate precipitation. The induced production of calcium carbonate formed by microorganisms has been widely used in environmental and engineering applications. The present study aimed to isolate, identify and optimize growth conditions of urease positive bacteria from urea rich soil in Gaza Strip. Bacterial isolates, which tolerated ≥10% urea concentration, were selected for the investigation. Eight isolates recovered and identified to be spore forming, urease positive, alkaliphile, halotolerant, and presumptively belonged to Bacillus species.  All isolates showed best growth at temperature 37°C, and pH 9-9.5. After exposure to UV irradiation, most isolates showed improved tolerance to urea concentration, however, other strains showed a decline in their adaption to urea concentrations. The mutant form of isolate in soil sample #3 showed the highest tolerance to urea concentrations at all exposure intervals, when compared with wild type. Moreover, all isolates precipitated calcium carbonate. The locally recovered isolates are promising contributors in the process of calcite Biomineralizaion and may be utilized in the remediation of concrete cracks, increase of compressive strength of concrete, decrease water permeability, and solve the problems of soil erosions.

Key words: Calcite bio-mineralization, microbial induced calcium carbonate precipitation (MICP), urease, Bacillus spp., Gaza strip.