A selected bacterial strain for the self-healing process in cementitious specimens without cell immobilization steps

Area of Science:

• Microbiology
• Materials Science
• Biotechnology

Background:

• Microbial bioprecipitation offers a sustainable approach to self-healing cementitious materials.
• Bacillus strains are promising candidates for inducing self-healing through biological processes.

Purpose of the Study:

• To identify and evaluate Bacillus strains for self-healing cement applications.
• To optimize fermentation conditions for enhanced bacterial growth and enzyme production.

Main Methods:

• Fermentation of five Bacillus strains to assess cell growth and urease production.
• 16S rDNA analysis and biochemical testing for strain identification (Bacillus cereus, Bacillus thuringiensis).
• Evaluation of glycerol's impact on bacterial concentration and urease activity.

Main Results:

• Glycerol addition significantly increased bacterial concentration (≈ 4.2 × 10^7 cells/mL) and urease production (≈ 3,623 U/mL).
• Bioprecipitation treatment after 40 days promoted crack self-healing in cementitious specimens.
• Compressive strength of treated specimens increased by approximately 14.2%.

Conclusions:

• Optimized Bacillus fermentation with glycerol is effective for self-healing cement.
• This biomineralization approach enhances the sustainability and engineering properties of cement-based materials.
• The study validates Bacillus cereus and Bacillus thuringiensis for microbial-induced calcite precipitation in construction materials.