Biocalcification, also known as microbiologically induced calcite precipitation (MICP), is a phenomenon involving the activity of the enzyme urease. A large number of soil microorganisms exhibit urease-producing ability. A novel application of MICP to improve properties of bricks by a soil bacteria Bacillus pasteurii NCIM 2477 was studied. Most of the deterioration of brick structures takes place because of the presence of moisture. Deposition of calcite on the surface and in voids of bricks reduces the water absorption substantially. A favorable effect of microbes to improve the durability of bricks by reducing water absorption was demonstrated as a novel concept in this paper.

Microbiologically induced calcite precipitation in bricks by bacterium Bacillus pasteurii (NCIM 2477) using a media especially optimized for urease production (OptU) was demonstrated in this study. Effect of biocalcification activity on compressive strength and water absorption capacity of bricks was investigated. Various other parameters such as pH, growth profile, urease activity, urea breakdown and calcite precipitated were monitored during the 28 days curing period. Efficiency of B. pasteurii to form microbial aided calcite precipitate in OptU media resulted into 83.9% increase in strength of the bricks as compared to only 24.9% with standard media, nutrient broth (NB). In addition to significant increase in the compressive strength, bricks treated with B. pasteurii grown in OptU media resulted in 48.9 % reduction in water absorption capacity as compared to control bricks immersed in tap water. Thus it was successfully demonstrated that microbial calcification in optimized media by Bacillus pasteurii has good potential for commercial application to improve the life span of structures constructed with bricks, particularly structures of heritage importance.

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