Influence of culturing media components on the growth and microbial induced calcium carbonate precipitation (MICP) activity of Lysinibacillus sphaericus

In order to identify appropriate environmental conditions and media components that are either essential or that enhance its growth and Microbial induced calcium carbonate precipitation (MICP) activity, in this study, a series of experiments were conducted to investigate the effects of media components and oxygen conditions on the growth rate and MICP activity of Lysinibacillus sphaericus strain MB 284. From these experiments, it was observed that aerobic conditions could lead to increased calcium carbonate production and up to three times faster growth rates by strain MB284 when compared to anoxic conditions. It was also determined that considering the measured growth rate, final biomass concentration, ureolysis activity, amount of calcium carbonate precipitation, and cost of media components for designing undefined culture media for industrial applications, yeast extract is the most economically appropriate option. In our attempts to grow strain MB284 in urea, sucrose, and ammonium acetate as its sole carbon source in minimal media, it was observed it is auxotrophic and that casamino acids and casein are essential for its growth. Even though our experiments agree with the literature that the addition of urea enhances the growth and MICP activity of L. sphaericus, it was discovered that when the initial urea concentration was greater than 3 g/l, the growth rate of strain MB284 can be temporarily inhibited until enough cells and urease are produced. These results reveal that the growth and MICP activity of strain MB284 during its application for bio-self healing can be highly dependent on environmental and nutrient conditions.