Attachment on mortar surfaces by cyanobacterium Gloeocapsa PCC 73106 and sequestration of CO2 by microbially induced calcium carbonate

The action and role of carbonatogenic microorganisms in bioconsolidation of stones

AIMS

Biomineralization is one of the first microbial strategies to cope with a changing environment during the evolution of life on Earth. Indeed, the coevolution of rocks and microorganisms induced massive microbial calcium carbonate precipitation, which played a fundamental role in shaping the Earth as we know it today. In the search for microbial strategies that can be developed to counteract global warming and meet the needs of the world's population, bacterial enzymes and metabolic activities have emerged as promising solutions.

METHODS AND RESULTS

Microbially induced calcium carbonate precipitation has received much attention for biotechnological applications such as carbon sequestration, the improvement of building materials and drug delivery. Thus, biomineralization covers many areas of interest from engineering to medicine, but curiously, we are far from knowing the biological dynamics that underlie this phenomenon.

CONCLUSIONS

This review discusses the role of microbes in calcium carbonate precipitation, with emphasis on carbonatogenic bacteria used in Cultural Heritage for sustainable bioconsolidation.

Bioconsolidation strategies for carbonate lithologies: Effectiveness and mechanisms in calcarenite, travertine, and marble

Toxic substances are often employed in conventional stone preservation techniques, whereas biorestoration offers material compatibility along with significant benefits for cultural heritage preservation, environmental safety, and sustainability. However, the application of this innovative technique to natural rocks is not fully understood. In this study, we evaluated the efficiency of a carbonatogenic bacterial strain (Lysinbacillus fusiformis 3.20) on three natural carbonate rocks: Calcarenite (CA), Travertine (TR) and Marble (MA), having different porosities. We integrated surface analyses (Field Emission Scanning Electron Microscopy, Atomic Force Microscopy, and X-Ray Diffraction) with bulk analyses (Porosity, Ultrasonic Wave Velocity, and Dynamic Elastic Moduli) to investigate the bioconsolidation processes. The results indicated that the biomineralization treatment had no effect on MA samples, while it improved the physical and mechanical properties of both CA and TR, evidenced by the formation of new bioprecipitates. Total and effective porosity decreased, particularly in CA, while ultrasonic wave velocities (Vp and Vs) and Young's modulus increased, with Poisson's ratio remaining unchanged. Comparative observations suggest that connected, randomly distributed, and low aspect ratio pores facilitate microbial activity by enabling deeper bacterial penetration into the stone, supporting nutrient distribution and the formation of calcium carbonate precipitates. When the treatment is effective, stiffness and strength are expected to increase due to reduced effective porosity, while resistance to shear deformation remains nearly constant, as does the relationship between porosity and wave velocities.

Advanced bacteria-based biomaterials for environmental applications

A large amount of anthropogenic CO2 emissions are derived from Portland cement production, contributing to global warming, which threatens human health and exposes flora and fauna to ecological imbalance. With concerns about the high maintenance and repair costs of concrete, the development of microbially induced calcium carbonate precipitation (MICP)-based self-healing concrete has been extensively examined. Bacterial carriers for microcrack healing could enhance the concrete's self-healing capacity by maintaining bacterial activity and viability. To reduce cement consumption, the development of sustainable engineered living materials (ELMs) based on MICP has become a promising new research topic that combines synthetic biology and material science, and they can potentially serve as alternatives to traditional construction materials. This review aims to describe bacterial carriers and the ongoing development of advanced ELMs based on MICP. We also highlight the emerging issues linked to applying MICP technology at the commercial scale, including economic challenges and environmental concerns.

Microbial induced carbonate precipitation for remediation of heavy metals, ions and radioactive elements: A comprehensive exploration of prospective applications in water and soil treatment

Improper disposal practices have caused environmental disruptions, possessing by heavy metal ions and radioactive elements in water and soil, where the innovative and sustainable remediation strategies are significantly imperative in last few decades. Microbially induced carbonate precipitation (MICP) has emerged as a pioneering technology for remediating contaminated soil and water. Generally, MICP employs urease-producing microorganisms to decompose urea (NH2CONH2) into ammonium (NH4+and carbon dioxide (CO2), thereby increasing pH levels and inducing carbonate precipitation (CO32-), and effectively removing remove contaminants. Nonetheless, the intricate mechanism underlying heavy metal mineralization poses a significant challenge, constraining its application in contaminants engineering, particularly in the context of prolonged heavy metal leaching over time and its efficacy in adverse environmental conditions. This review provides a comprehensive idea of recent development of MICP and its application in environmental engineering, examining metabolic pathways, mineral precipitation mechanisms, and environmental factors as well as providing future perspectives for commercial utilization. The use of ureolytic bacteria in MICP demonstrates cost-efficiency, environmental compatibility, and successful pollutant abatement over tradition bioremediation techniques, and bio-synthesis of nanoparticles. limitations such as large-scale application, elevated Ca2+levels in groundwater, and gradual contaminant release need to be overcome. The possible future research directions for MICP technology, emphasizing its potential in conventional remediation, CO2 sequestration, bio-material synthesis, and its role in reducing environmental impact for long-term economic benefits.

Impact of bacterial admixtures on the compressive and tensile strengths, permeability, and pore structure of ternary mortars: Comparative study of ureolytic and phototrophic bacteria

The addition of bacterial biomass to cementitious materials can improve strength and permeability properties by altering the pore structure. Photoautotrophic bacteria are understudied mortar bio-additives that do not produce unwanted by-products compared to commonly studied ureolytic species. This study directly compares the impact of the addition of heterotrophic Bacillus subtilis to photoautotrophic Synechocystis sp. PCC6803 on mortar properties and microstructure. Cellulose fibers were used as a bacteria carrier. A commercial concrete healing agent composed of dormant bacterial spores was also tested. Strength, water absorption tests, mercury intrusion porosimetry, differential scanning calorimetry, thermogravimetric analysis, and scanning electron microscopy were applied to experimental mortar properties. The photoautotrophic modifications had a stronger positive impact on mortar strength and permeability properties than sporulated heterotrophic modifications due to differences in surface properties and production of exopolysaccharides. The findings provide support for photoautotrophic species as additives for mortars to move away from ammonia-generating species.

Microbial-induced calcium carbonate precipitation: Influencing factors, nucleation pathways, and application in waste water remediation

Microbial-induced calcium carbonate precipitation (MICP) is a technique that uses the metabolic action of microorganisms to produce CO₃^2- which combines with free Ca²⁺ to form CaCO₃ precipitation. It has gained widespread attention in water treatment, aimed with the advantages of simultaneous removal of multiple pollutants, environmental protection, and ecological sustainability. This article reviewed the mechanism of MICP at both intra- and extra-cellular levels. It summarized the parameters affecting the MICP process in terms of bacterial concentration, ambient temperature, etc. The current status of MICP application in practical engineering is discussed. Based on this, the current technical difficulties faced in the use of MICP technology were outlined, and future research directions for MICP technology were highlighted. This review helps to improve the design of existing water treatment facilities for the simultaneous removal of multiple pollutants using the MICP and provides theoretical reference and innovative thinking for related research.

Influencing factors on ureolytic microbiologically induced calcium carbonate precipitation for biocementation

Microbiologically induced calcium carbonate precipitation (MICP) is a technique that has received a lot of attention in the field of geotechnology in the last decade. It has the potential to provide a sustainable and ecological alternative to conventional consolidation of minerals, for example by the use of cement. From a variety of microbiological metabolic pathways that can induce calcium carbonate (CaCO₃) precipitation, ureolysis has been established as the most commonly used method. To better understand the mechanisms of MICP and to develop new processes and optimize existing ones based on this understanding, ureolytic MICP is the subject of intensive research. The interplay of biological and civil engineering aspects shows how interdisciplinary research needs to be to advance the potential of this technology. This paper describes and critically discusses, based on current literature, the key influencing factors involved in the cementation of sand by ureolytic MICP. Due to the complexity of MICP, these factors often influence each other, making it essential for researchers from all disciplines to be aware of these factors and its interactions. Furthermore, this paper discusses the opportunities and challenges for future research in this area to provide impetus for studies that can further advance the understanding of MICP.