Biocalcifying Bacillus subtilis cells effectively consolidate deteriorated Globigerina limestone

Area of Science:

• Geology
• Microbiology
• Conservation Science

Background:

• Ancient limestone structures are susceptible to deterioration.
• Natural microbially induced calcite precipitation (MICP) can consolidate limestone.
• Existing conservation methods may alter stone properties or be less eco-friendly.

Purpose of the Study:

• To investigate the efficacy of biocalcifying bacteria for consolidating deteriorated limestone.
• To evaluate the mechanical and physical improvements in treated limestone.
• To assess the eco-friendliness and industrial relevance of the biomineralization treatment.

Main Methods:

• Deteriorated limestone samples were treated with Bacillus subtilis.
• Mechanical tests (e.g., drilling resistance) were performed.
• Physical properties (salt resistance, water absorption, porosity) were analyzed.

Main Results:

• Bacillus subtilis achieved uniform bioconsolidation to a depth of 30 mm.
• Drilling resistance increased significantly, comparable to freshly quarried limestone.
• Treated limestone exhibited enhanced salt resistance, reduced water absorption, and preserved porosity (±6%).

Conclusions:

• Biomineralization using Bacillus subtilis is an effective and eco-friendly method for limestone consolidation.
• The treatment preserves the natural properties and pore network of limestone.
• This biomineralization technique shows industrial relevance and compares favorably with commercial stone consolidants.