A novel approach to accelerate bacterially induced calcium carbonate precipitation using oxygen releasing compounds (ORCs)

Insights into the Current Trends in the Utilization of Bacteria for Microbially Induced Calcium Carbonate Precipitation

Nowadays, microbially induced calcium carbonate precipitation (MICP) has received great attention for its potential in construction and geotechnical applications. This technique has been used in biocementation of sand, consolidation of soil, production of self-healing concrete or mortar, and removal of heavy metal ions from water. The products of MICP often have enhanced strength, durability, and self-healing ability. Utilization of the MICP technique can also increase sustainability, especially in the construction industry where a huge portion of the materials used is not sustainable. The presence of bacteria is essential for MICP to occur. Bacteria promote the conversion of suitable compounds into carbonate ions, change the microenvironment to favor precipitation of calcium carbonate, and act as precipitation sites for calcium carbonate crystals. Many bacteria have been discovered and tested for MICP potential. This paper reviews the bacteria used for MICP in some of the most recent studies. Bacteria that can cause MICP include ureolytic bacteria, non-ureolytic bacteria, cyanobacteria, nitrate reducing bacteria, and sulfate reducing bacteria. The most studied bacterium for MICP over the years is Sporosarcina pasteurii. Other bacteria from Bacillus species are also frequently investigated. Several factors that affect MICP performance are bacterial strain, bacterial concentration, nutrient concentration, calcium source concentration, addition of other substances, and methods to distribute bacteria. Several suggestions for future studies such as CO₂ sequestration through MICP, cost reduction by using plant or animal wastes as media, and genetic modification of bacteria to enhance MICP have been put forward.

Microbially induced calcium carbonate precipitation: a widespread phenomenon in the biological world

Biodeposition of minerals is a widespread phenomenon in the biological world and is mediated by bacteria, fungi, protists, and plants. Calcium carbonate is one of those minerals that naturally precipitate as a by-product of microbial metabolic activities. Over recent years, microbially induced calcium carbonate precipitation (MICP) has been proposed as a potent solution to address many environmental and engineering issues. However, for being a viable alternative to conventional techniques as well as being financially and industrially competitive, various challenges need to be overcome. In this review, the detailed metabolic pathways, including ammonification of amino acids, dissimilatory reduction of nitrate, and urea degradation (ureolysis), along with the potent bacteria and the favorable conditions for precipitation of calcium carbonate, are explained. Moreover, this review highlights the potential environmental and engineering applications of MICP, including restoration of stones and concrete, improvement of soil properties, sand consolidation, bioremediation of contaminants, and carbon dioxide sequestration. The key research and development questions necessary for near future large-scale applications of this innovative technology are also discussed.

Application of microbially induced calcium carbonate precipitation in designing bio self-healing concrete

Concrete is one of the most broadly used construction materials in the world due to its number of performance characteristics. Despite the long life of concrete structure under ideal conditions, it tends to crack and this phenomenon results in a considerable reduction in service life and performance. Evidence of microbial involvement in the precipitation of minerals has led to a massive investigation on adapting this technology for addressing the concrete cracking issue. Calcium carbonate is one of most compatible materials with the concrete constituents and it can be induced via biological process. In this review paper, the effects of different factors, such as nucleation site, pH, nutrient and temperature, on the biosynthesis of calcium carbonate are elucidated. Moreover, the influences of effective factors on calcium carbonate polymorphism are extensively elaborated. Finally, the limitations for the future application of this innovative technology in construction industry are highlighted.

Microbial calcium carbonate precipitation with high affinity to fill the concrete pore space: nanobiotechnological approach

Despite the advantages of concrete, it has a pore structure and is susceptible to cracking. The initiated cracks as well as pores and their connectivity accelerate the structure degradation by permitting aggressive substances to flow into the concrete matrix. This phenomenon results in a considerable repair and maintenance costs and decreases the concrete lifespan. In recent years, biotechnological approach through immobilization of bacteria in/or protective vehicles has emerged as a viable solution to address this issue. However, the addition of macro- or micro scale size particles can decrease the integrity of matrix. In this study, the immobilization of bacteria with magnetic iron oxide nanoparticle (ION) was proposed to protect the bacterial cell and evaluate their effect on healing the concrete pore space. The results show that the addition of immobilized bacteria with IONs resulted in a lower water absorption and volume of permeable pore space. Crystal analysis using scanning electron microscope (SEM) and energy dispersive X-ray spectroscopy (EDS) revealed that CaCO₃ was precipitated in bio-concrete specimen as a result of microbial biosynthesis.

Mechanical properties of bio self-healing concrete containing immobilized bacteria with iron oxide nanoparticles

Concrete is arguably one of the most important and widely used materials in the world, responsible for the majority of the industrial revolution due to its unique properties. However, it is susceptible to cracking under internal and external stresses. The generated cracks result in a significant reduction in the concrete lifespan and an increase in maintenance and repair costs. In recent years, the implementation of bacterial-based healing agent in the concrete matrix has emerged as one of the most promising approaches to address the concrete cracking issue. However, the bacterial cells need to be protected from the high pH content of concrete as well as the exerted shear forces during preparation and hardening stages. To address these issues, we propose the magnetic immobilization of bacteria with iron oxide nanoparticles (IONs). In the present study, the effect of the designed bio-agent on mechanical properties of concrete (compressive strength and drying shrinkage) is investigated. The results indicate that the addition of immobilized Bacillus species with IONs in concrete matrix contributes to increasing the compressive strength. Moreover, the precipitates in the bio-concrete specimen were characterized using scanning electron microscope (SEM), X-ray diffraction (XRD), and energy-dispersive X-ray spectroscopy (EDS). The characterization studies confirm that the precipitated crystals in bio-concrete specimen were CaCO₃, while no precipitation was observed in the control sample.

Bio-reinforced self-healing concrete using magnetic iron oxide nanoparticles

Immobilization has been reported as an efficient technique to address the bacterial vulnerability for application in bio self-healing concrete. In this study, for the first time, magnetic iron oxide nanoparticles (IONs) are being practically employed as the protective vehicle for bacteria to evaluate the self-healing performance in concrete environment. Magnetic IONs were successfully synthesized and characterized using different techniques. The scanning electron microscope (SEM) images show the efficient adsorption of nanoparticles to the Bacillus cells. Microscopic observation illustrates that the incorporation of the immobilized bacteria in the concrete matrix resulted in a significant crack healing behavior, while the control specimen had no healing characteristics. Analysis of bio-precipitates revealed that the induced minerals in the cracks were calcium carbonate. The effect of magnetic immobilized cells on the concrete water absorption showed that the concrete specimens supplemented with decorated bacteria with IONs had a higher resistance to water penetration. The initial and secondary water absorption rates in bio-concrete specimens were 26% and 22% lower than the control specimens. Due to the compatible behavior of IONs with the concrete compositions, the results of this study proved the potential application of IONs for developing a new generation of bio self-healing concrete.