A feasible scale-up production of Sporosarcina pasteurii using custom-built stirred tank reactor for in-situ soil biocementation

Production of urease enzyme from ureolytic bacteria (e.g. Sporosarcina pasteurii) is essential for precipitation of CaCO3. This bioprocess is notably utilized for soil improvement, biocementation and bioremediation of heavy metals. Despite the viability for field-scale implementation as a suitable alternative to conventional treatment methods, most reports in the literature are constrained to laboratory-scale. Thus, this study demonstrates an economic strategy to scale-up the production and cultivation of ureolytic bacteria using a custom-built stainless steel stirred tank reactor (3 m(3)). Scalability of the bacterial cells was carried out from 214 L to 2400 L seed cultures for 90 h. Technical-grade ingredients (food-grade yeast extract media and chemicals) were used for scale-up production of the bacterial cells. The growth profile, pH and urease activity were subsequently monitored throughout the in-situ production period. Biocementation on sand mould specimens was also performed using bacterial cultures obtained from the reactor and low-grade cementation reagents. The sand columns were grouped into different treatment cycles to determine the effect of ureolysis. CaCO3 content, effluent pH and microstructural analyses (scanning electron microscopy with energy dispersive X-ray spectroscopy) of the treated soil samples were also evaluated. The results show that scale-up production of ureolytic bacteria cells under nonsterile conditions using a custom-built reactor for industrial MICP application is feasible.