Genomic and functional characterization of ureolytic Bacillus bombysepticus QCSJ3 and its application in self-healing cementitious composites through encapsulation.

Developing sustainable, long-lasting building materials is essential for reducing the environmental footprint of civil infrastructure and addressing global climate challenges. This study presents a microbial-based strategy for healing cracks in cementitious composites, aiming to extend structural durability and reduce the need for carbon-intensive repairs. An autochthonous ureolytic strain was isolated from carbonate-rich soils in southern Brazil and identified as Bacillus bombysepticus QCSJ3 through whole-genome sequencing. Functional annotation revealed that B. bombysepticus QCSJ3 possesses the genetic machinery required for calcium carbonate precipitation through the ureolytic pathway and its associated genetic components. The strain was incorporated during the mixing and molding of cementitious specimens in both free and encapsulated forms, with or without urea Supplementation. After 70 days, specimens treated with encapsulated B. bombysepticus QCSJ3 in the presence of urea exhibited complete (100%) healing of cracks up to 400 μm, as well as a 19% increase in tensile strength. Free-form application also demonstrated substantial crack closure (up to 86%). These results demonstrate the feasibility of integrating microbial biotechnology with building materials to develop self-healing composites that reduce repair frequency, extend service life, and promote climate-resilient infrastructure. This study provides both genomic and functional evidence Supporting the use of encapsulated ureolytic microorganisms as a scalable and eco-efficient solution aligned with the Sustainable Development Goal 13 (SDG13) - Climate Action.