Induced Calcium Carbonate Research Articles

Bioaugmentation of Industrial Wastewater and Formation of Bacterial–CaCO3 Coupled System for Self-Healing Cement

This study investigates the potential of bioaugmentation with Bacillus species to enhance wastewater treatment and develop a bacterial–CaCO3 system for self-healing cement applications. Utilizing microbiologically induced calcium carbonate precipitation (MICP), this study evaluates the dual functionality of Bacillus licheniformis and B. muralis strains. For wastewater treatment, the bioaugmentation process achieved significant pollutant reductions, including a 99.52% decrease in biochemical oxygen demand (BOD5), a 92.13% reduction in chemical oxygen demand (COD), and a substantial removal of heavy metals and nutrients. This process also produced high concentrations of CaCO3 precipitate enriched with viable bacterial cells, demonstrating an eco-friendly approach to improving water quality. For self-healing cement applications, bioaugmented CaCO3 crystals were coated with nutrient and sodium silicate layers to form a bacterial–CaCO3 coupled system. This system demonstrated a 92% recovery in compressive strength after 180 days, highlighting its ability to autonomously repair microcracks in cement-based materials. The layered encapsulation strategy ensured bacterial viability and a controlled activation mechanism, offering a scalable and sustainable solution for infrastructure resilience. This dual-function approach addresses critical environmental and construction challenges by linking efficient wastewater treatment with innovative self-healing material development, contributing to global sustainability and circular economy goals.

A Comprehensive Review of Biomaterials Synthesized Using the MICP Process for Sustainable Construction

Building materials and infrastructure contribute to approximately 13% of global CO₂ emissions annually, according to the International Energy Agency (IEA, 2022). This underscores the urgent need to transition to more sustainable construction materials. Emerging biomaterials, developed through innovative processes such as the Microbially Induced Calcium Carbonate Precipitation (MICP) process, are being explored as potential alternatives to conventional materials. These biomaterials, including bio-concrete, bio- cement, and bio-bricks, are produced using waste materials and biological processes, such as bacteria and plant-based resources that act as carbon sinks, offering an eco-friendly solution to construction challenges. Many researchers and companies are actively experimenting with these materials to solve pressing environmental problems, with promising results. However, challenges remain in optimizing these materials for large-scale production and ensuring their performance under real-world conditions. Despite these obstacles, ongoing research is continually pushing the boundaries of biomaterials' potential in construction, with numerous studies focused on improving their properties and addressing current limitations. This paper provides a comprehensive review of the advantages and disadvantages of biomaterials in comparison to traditional construction materials. It explores how these bio- based materials—synthesized through the MICP process—can offer significant benefits, such as self-healing properties, low-cost production, and reduced environmental impact. The review also discusses the challenges that still need to be overcome and the ongoing research aimed at making biomaterials a viable alternative to conventional materials. As part of the field of engineering, this paper highlights the critical role of biotechnology in advancing sustainable construction practices and the continued evolution of biomaterials in engineering applications.

Exploration of urease-aided calcium carbonate mineralization by enzyme analyses of Neobacillus mesonae strain NS-6.

Urease containing nickel cofactor is crucial for urea-hydrolytic induced calcium carbonate (CaCO3) precipitation (UICP). However, limited information exists regarding the influence of amino acid residues interacting with nickel ions in its structure on induced CaCO3 mineralization. Herein, RT-qPCR was used to demonstrate that the addition of NiCl2 dramatically upregulated the expression of urease structural gene ureC that was correlated with nickel binding in Neobacillus mesonae strain NS-6. Homology modeling and molecular docking were employed to construct the three-dimensional structure of urease and seek the key residues involved in nickel binding process, and virtual mutation technology was adopted to inform three key residues coordinated with nickel ions and urea, His249, His275, and Asp363. Four metrics, including root mean square deviation values for mutations of those key residues in urease-urea complexes severally and wild-type, were calculated by molecular dynamics simulations when they were mutated into alanine, respectively. Subsequently, the mutations of H249A, H275A, and D363A were characterized using western blotting to reveal a decrease in the relative expression and activity of urease, along with a corresponding reduction in CaCO3 precipitation. Ultimately, the mutations also exhibited that they had lower substrate affinity and catalytic efficiency for urea through enzymatic properties analysis. The findings suggested that those residues played a pivotal role in UICP of strain NS-6, which would expand the theoretical basis for modulating urease activity.IMPORTANCEUrease-producing bacterium is of great importance in diverse application fields, such as environmental remediation, due to its key driving characteristics in catalyzing urea hydrolysis via urea-hydrolytic induced CaCO3 precipitation (UICP). As essential cofactors of urease, nickel ions play a crucial role in regulating urease catalysis and maintaining structural stability. Numerous investigations have emphasized the impact of nickel ions on urease activity in recent years, to our best knowledge, only a few literatures have studied the molecular-level regulation of nickel-ligand residues. This study focused on the highly urease-producing bacterial Neobacillus mesonae NS-6 to explore the effects of specific nickel-ligand residues on the urease-aided CaCO3 mineralization process using molecular simulation predictions and targeted mutation experiments. The aim was to provide a molecular-level understanding of the interactive effects between urea and critical residues associated with the urease active center, as well as propose an effective modification strategy to enhance the application of UICP in future environmental areas.

Modeling the uncoupled damage-healing behavior of self-healing cementitious material with phase-field method

Microbially induced calcium carbonate precipitation (MICCP), which is a biochemical process that utilizes microbial metabolic activities to precipitate calcium carbonate (CaCO3), can be used for damage-healing by crack filling. In this study, we develop a computational uncoupled damage-healing framework to predict the fracture-healing responses of a multifunctional vascular cementitious composite. The framework integrates a numerical model for self-healing cementitious materials into a damage model developed using the phase-field method. The numerical self-healing model is utilized to compute the MICCP healing based on the chemical and enzyme kinetics of microbial activities, whereas the phase-field method is employed to capture the fracture response of the material. This framework comprises three stages: Stage 1 — damage, Stage 2 — healing, and Stage 3 — re-damage of the healed structure. Using the load–displacement curve of the healed cementitious material, the proposed uncoupled damage-healing models can predict the recovery in material stiffness based on the MICCP healing ratio. The proposed framework can be applied to a wide range of fracture-healing problems in self-healing cementitious materials utilizing MICCP as the healing methodology.

Effect of Exposure Environment and Calcium Source on the Biologically Induced Self-Healing Phenomenon in a Cement-Based Material

Microbially induced calcium carbonate precipitation (MICP) presents a sustainable, environmentally friendly solution for repairing cracks in cement-based materials, such as mortar and concrete. This self-healing approach mechanism enables the matrix to autonomously close its own cracks over time. In this study, specimens (50 mm in diameter and 25 mm in height) were exposed to submersion and a wet–dry cycle environment. The solution considered a nutrient-rich suspension with calcium lactate, urea, calcium nitrate, and Bacillus subtilis or Sporosarcina pasteurii in a biomineralization approach. The self-healing efficiency was assessed through optical microscopy combined with image processing, focusing on the analysis of the superficial crack closure area. S. and B. subtilis exhibited notable capabilities in effectively healing cracks, respectively, 8 mm2 and 5 mm2 at 35 days. Healing was particularly effective in samples placed in a submerged environment, especially with a 69 mM concentration of calcium lactate in bacterial suspensions containing B. subtilis, where 87.5% of a 4 mm2 crack was closed within 21 days. In contrast, free calcium ions in the solution, resulting from anhydrous cement hydration, proved ineffective for S. pasteurii biomineralization in urea-rich environments. However, the addition of an external calcium source (calcium nitrate) significantly enhanced crack closure, emphasizing the critical role of calcium availability in optimizing MICP for bio-agents in cement-based materials. These findings highlight the potential of MICP to advance sustainable self-healing concrete technologies.

Complete genome sequence of Sporosarcina pasteurii type strain DSM33.

Here, we present the complete genome sequence of Sporosarcina pasteurii type strain DSM33, a model organism for microbially induced calcium carbonate precipitation. This genome consists of a single 3.3-Mb chromosome and is an improvement upon draft S. pasteurii genome sequences currently available in public databases.

Enhancing crack self-healing properties of low-carbon LC3 cement using microbial induced calcite precipitation technique

Limestone Calcined Clay Cement (LC3) is a promising low-carbon alternative to traditional cement, but its reduced clinker content limits its self-healing ability for microcracks, affecting durability. This study explores the application of Microbial Induced Calcite Precipitation (MICP) technique to enhance the crack self-healing capacity of LC3-based materials. Bacillus pasteurii was utilized to induce calcium carbonate precipitation to improve the crack self-healing capacity of LC3, thereby addressing its limited durability due to reduced clinker content. Experimental tests focused on optimizing the growth conditions for B. pasteurii, evaluating the compressive strength, capillary water absorption, and crack self-healing rates of the modified LC3 material. Results showed that under optimal conditions (pH of 9, inoculation volume of 10%, incubation temperature of 30°C, and shaking speed of 150 rpm), the bacterial strain exhibited maximum metabolic activity. The Microbe-LC3 mortar demonstrated a self-healing rate of up to 97% for cracks narrower than 100 μm, significantly higher than unmodified LC3. Additionally, the compressive strength of Microbe-LC3 was enhanced by approximately 15% compared to standard LC3 mortar after 28 days. The capillary water absorption was reduced, indicating improved durability due to the microbial-induced calcium carbonate filling the pores. This study confirms that MICP technology is a viable approach to significantly enhance the performance of LC3, contributing to the development of more durable and sustainable cementitious materials for construction applications.

A One-Dimensional Reactive Transport Model for Microbially Induced Calcium Carbonate Precipitation (MICP) in Phreeqc

Microbially induced calcium carbonate precipitation (MICP) is a geotechnical solution with a low ecological footprint. Conducting MICP inside a porous medium can be used for biocementation. Despite many models and tools being published for simulating MICP, a computationally light, easy-to-use, and freely-available simulation tool is lacking. In this work, we present a reactive transport model using the native capabilities of the Phreeqc software (a free and open-source geochemical solver). We model MICP inside a column packed with sands and inoculated with bacteria. Our model is a one-dimensional representation of the column that accounts for the kinetics of precipitation and ureolysis as well as porosity change. We verify our model by simulating previously published MICP experiments to show our model gives reasonably well predictions. Sensitivity analysis of our model’s input parameters and discussions around their range are presented. Additionally, we calculate the supersaturation of calcite as a function of space and time—a feature that could be important for precipitation, but it is commonly ignored in MCIP modeling. Our scripts developed for running simulations are accessible publicly. Due to the low computational effort required for the simulations, our Phreeqc scripts can be used to design and test different treatment recipes for conducting MICP.

Improvement of the Sand Quality by Applying Microorganism Induced Calcium Carbonate Precipitation to Reduce Cement Usage

This research aimed to study the utilization of microorganisms in the soil. These microorganisms were applied to improve the quality of soil and sand to reduce cement consumption. The process of microbial-induced precipitation of calcium carbonate (MICP) was used in this study, a bonding process to create a binding between sand particles from the naturally occurring processes of microorganisms. The study was conducted to determine the maximum growth rate of bacteria (maximum growth curve) of five strains as follows Proteus mirabilis TISTR 100, Bacillus thuringiensis TISTR 126, Staphylococcus aureus TISTR 118, Bacillus sp. TISTR 658 and Bacillus megaterium TISTR 067 in Nutrient Broth (NB) culture medium at 37°C. Christensen's Urea Agar slant (UA) was a preliminary screen for urease-producing bacteria. The color change of indicator color was seen in the slant, comparing the results (+) and control (-). The researchers have selected bacterial strains capable of producing significant amounts of enzymes to hydrolyze urea. It was found that the amount of calcium carbonate sediment produced by five strains of bacteria, namely Proteus mirabilis TISTR 100, Bacillus thuringiensis TISTR 126, Staphylococcus aureus TISTR 118, Bacillus sp. TISTR 658 and Bacillus megaterium TISTR 067 had the amount of sediment produced as follows: 3.430, 3.080, 2.590, 1.985, and 1.615 mg/ml, respectively. It was found that the species Bacillus sp. TISTR 658 does not produce the most calcium carbonate sediment. Nevertheless, it made the sand samples stick together tightly and form the perfect lumps. Therefore, improving the sand's composition has shown the potential to apply the MICP process to reduce the cement used.

Bacillus cereus GS-5 immobilized sintered fly ash lightweight aggregate for strength, durability, and autonomous crack healing in bacterial concrete

This paper investigates the impact of ureolytic bacteria, specifically Bacillus cereus GS-5 immobilized sintered fly ash lightweight aggregate, on the self-healing, strength, and durability characteristics of the bacterial concrete. Different concentrations of bacterial cells (105 to 107 cells/mL) were used, and a part of conventional aggregate was replaced by microbe immobilized lightweight aggregate as part of producing concrete mixes. Various systematic tests, such as compressive strength, water absorption, rapid chloride permeability, and self-healing capability, were conducted after defined time intervals. The results of the experiments demonstrated that the compressive strength of the bacterial concrete increased by an average of 25.65% as compared to the control specimens. A simulated crack width of 0.5mm was successfully effectively healed in the specimen by microbial induced calcium carbonate precipitation. The SEM images confirmed the precipitation, structure, and dispersion of the calcium carbonate crystals, whereas XRD analysis revealed the formation of the calcite crystalline phases within the calcium carbonate crystals. Calcite precipitation resulted in reduced porosity of the bacterial concrete, which was confirmed by reduced chloride permeability (5% - 17%), water permeability (29% - 60%), and water absorption (3% - 32%) with respect to the control specimen. It has been concluded that Bacillus cereus GS-5 immobilized sintered fly ash lightweight aggregate would serve as an effective concrete admixture, providing advantages such as self-healing of cracks, better durability, and improved mechanical performances.

Experimental and simulation study of calcium carbonate non-uniform distribution characteristics of bio-cemented sand

The innovative technology of microbially induced calcium carbonate precipitation (MICP) soil modification is widely used in soil reinforcement, soil remediation, environmental remediation and other fields, and has gradually become a hot research direction. Recent research is more focused on the overall physical and mechanical characteristics of the uniform reinforced specimen. There is limited research on the distribution characteristics of calcium carbonate along the seepage path during the reinforcement process. However, the distribution characteristics of calcium carbonate play a significant role in the physical and mechanical characteristics of the solid, especially in the large-scale MICP reinforcement process. In this study, based on the microbial mineralization reaction tests of different concentrations of cement solution at the laboratory sample scale, the calcium carbonate distribution on the surface of the sample at the microscale SEM observation and the CT scanning reconstruction of the micro pore structure characteristics of the microbial reinforced soil, we discussed the characteristics of the non-uniform reduction of calcium carbonate distribution and porosity in the process of microbial consolidation. Based on the Kozeny-Carman equation, the conceptual model of effective porosity was introduced, and the time relationship between porosity and calcium carbonate precipitation was considered to establish a bio-chemical-seepage multi-physics field coupling model. The precipitation of calcium carbonate in the axial direction of the model sample exhibits an uneven feature of more at the top and less at the bottom, and the distribution characteristics of porosity also show an uneven feature of more at the top and less at the bottom.

Evaluation of encapsulated Bacillus subtilis bio-mortars for use under acidic conditions

This research aimed to examine the effects of an acidic environment on the mechanical properties and durability of bio-mortar (BM) encapsulated with Bacillus subtilis bacteria, in comparison to normal mortar (NM). The results at 28 days indicated that both 3% and 6% HCl significantly increased the compressive strength of the BM by 25% and 50%, respectively, compared with that of the NM. However, when 11% HCl was introduced, the compressive strength of the BM decreased to 50% lower than that of the NM. Furthermore, the water absorption rate of the BM was 33% lower than that of the NM. The mass loss for both 3% and 6% HCl was comparable, whereas at 11% HCl, BM experienced a mass loss that was 68% greater than that of NM. These findings suggest that with 3% and 6% HCl, the microbially induced calcium carbonate precipitation (MICP) process effectively generated CaCO3, which filled the pores and enhanced the structural integrity of the BM, leading to improved compressive strength and durability. Conversely, at 11% HCl, the MICP benefits in BM were diminished due to adverse environmental conditions that negatively affected the bacterial cells, highlighting the limitations of the HCl concentration for optimizing MICP efficiency in mortar.

Insights into self-healing capacity of cement matrix containing high-efficiency bacteria under challenging conditions

This study provides novel insights into enhancing the self-healing capacity of cement matrix through the integration of natural Bacillus isolates derived from leached and calcified soils. The challenging and highly alkaline environment of cement matrix typically impedes bacterial activity, making the successful application of these bacteria in such conditions particularly significant. In this research, Bacillus licheniformis-Bacillus muralis co-culture was identified as highly effective in inducing calcium carbonate precipitation, a critical factor for self-healing. The selected co-cultured bacterial activity resulted in the formation of up to 2.885 g/100 mL of CaCO₃, while the co-culture's effectiveness was demonstrated by the complete repair of a 0.5 mm crack within 96 h demonstrating a repair rate of approximately 0.125 mm per 24 h. Furthermore, the study showed that the bacterial co-culture could survive and remain active under varying environmental conditions, including wet-dry cycles and extreme pH levels, which are typical of construction sites. This rapid crack closure, achieved without additional protective measures for the bacteria, marks a significant advancement in the application of microbial co-cultures for enhancing the durability of cement-based materials. The study also provides a detailed analysis of bacterial behavior under various environmental stresses typical of construction sites, highlighting the robustness and practical applicability of this biotechnological approach. As the long-term output, the obtained results represent a substantial advancement in the practical application of microbial co-cultures for self-healing effect of cement-based materials.

Comparison and mechanism study on solidification of loose pisha sandstone by indigenous bacteria and sporosarcina pasteurii

Pisha sandstone is a kind of sandstone which is easy to collapse by water in Shanxi, Shaanxi and Inner Mongolia of China, and suffers from hydraulic erosion all the year round. In recent years, some scholars have used microbial induced calcium carbonate precipitation (MICP) technology to solidify Pisha sandstone to improve the water erosion resistance of Pisha sandstone. However, for the climate environment with low average temperature in Pisha sandstone area, the commonly used Sporosarcina pasteurii are not well adapted. The purpose of this study is to use the indigenous strainsto solidify the loose Pisha sandstone, and to compare the growth adaptability, mechanical properties and water erosion resistance of the solidified layer with Sarcina pasteurii at different temperatures, and to explore the mechanism of different temperatures and strains affecting the microbial solidification of Pisha sandstone from the micro scale. At the same time, a mixed bacterial liquid solidification test was also set up. The results showed that the solidified thickness of indigenous strains was 4.65 % higher than that of Sporosarcina pasteurii, and the thickness and strength of mixed strains were increased by 19.57 % and 36.62 %, respectively. The growth and solidification effect of indigenous strains were less affected by low temperature. Compared with Sporosarcina pasteurii, at low temperature, the bacterial concentration decrease of indigenous strains was reduced by 26.13 %, the thickness loss of solidified layer was reduced by 13.04 %, and the strength loss of solidified layer was reduced by 13.39 %. The effect of low temperature on the growth of bacteria is mainly reflected in affecting the maximum concentration of bacteria and the growth rate. The effect on MICP mainly reflected in affecting the life activities of bacteria and the crystal form and morphology of calcium carbonate. The research results provide a theoretical basis for the MICP technology application of indigenous strains and multi-strains in Pisha sandstone area soil reinforcement and solidification slope.

Visualising the strength development of FICP-treated sand using impedance spectroscopy

Fungal Induced Calcium Carbonate Precipitation (FICP) is a novel method used in geotechnical engineering that enhances the engineering properties of sand by using the potential of fungal activity. This research is the first attempt to monitor the strength of FICP treated sand using embedded Piezoelectric (PZT) patch based Electromechanical Impedance (EMI) spectroscopy. In the past, the strength of such treated sand has been determined through the destructive methods like Unconfined Compressive Strength (UCS) test. In this study, the sand is mixed with the filamentous fungus Aspergillus Niger and the cementation solution (urea and \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\:{\ ext{C}\ ext{a}\ ext{C}\ ext{l}}_{2}$$\\end{document} in the ratio of 1:1) is injected after every 24 h. Results recorded from the cost-effective EVAL AD5933 chip indicate that the shifting of frequency impedance signals in each phase is in good alignment with UCS and calcium carbonate content (CCC). Following the 28-day treatment period, the treated sand achieves a maximum UCS of 3.93 MPa, accompanied by a CCC of 15.19%. In order to correlate EMI signals with treatment cycles, UCS, and CCC, various multi linear regression (MLR) equations for statistical metrics like root mean square deviation (RMSD), mean absolute percentage deviation (MAPD), and correlation coefficient deviation (CCD) are developed. Additionally, Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray (EDX) analyses have been conducted to observe the success of the FICP process in the sand.

Study on Dynamic Strength Characteristics of Sand Solidified by Enzyme-Induced Calcium Carbonate Precipitation (EICP).

Saturated sand foundations are susceptible to liquefaction under dynamic loads. This can result in roadbed subsidence, flotation of underground structures, and other engineering failures. Compared with the traditional foundation reinforcement technology, enzyme-induced calcium carbonate precipitation technology (EICP) is a green environmental protection reinforcement technology. The EICP technology can use enzymes to induce calcium carbonate to cement soil particles and fill soil pores, thus effectively improving soil strength and inhibiting sand liquefaction damage. The study takes EICP-solidified standard sand as the research object and, through the dynamic triaxial test, analyzes the influence of different confining pressure (σ3) cementation times (CT), cyclic stress ratio (CSR), dry density (ρd), and vibration frequency (f) on dynamic strength characteristics. Then, a modified dynamic strength model of EICP-solidified standard sand was established. The results show that, under the same confining pressure, the required vibration number for failure decreases with the increase in dynamic strength, and the dynamic strength increases with the rise in dry density. At the same number of cyclic vibrations, the greater the confining pressure and cementation times, the greater the dynamic strength. When the cementation times are constant, the dynamic strength of EICP-solidified sand decreases with the increase in the vibration number. When cementation times are 6, the dynamic strength of the specimens with CSR of 0.35 is 25.9% and 32.4% higher than those with CSR of 0.25 and 0.30, respectively. The predicted results show that the model can predict the measured values well, which fully verifies the applicability of the model. The research results can provide a reference for liquefaction prevention in sand foundations.

Role of bacteria on bio-induced calcium carbonate formation: insights from droplet microfluidic experiments

Microbially induced calcium carbonate precipitation (MICP) has emerged as a promising solution for geotechnical issues. However, the role of bacteria in the formation of calcium carbonate (CaCO3) remains incompletely understood. In this study, a droplet microfluidic chip was developed to observe the growth process of calcium carbonate and bacterial behaviour during the MICP process under various bacterial density conditions. Scanning electron microscope was then utilised to analyse the calcium carbonate morphology, and Raman spectroscopy was employed to identify calcium carbonate polymorphs. Nucleation within microspaces showed a stochastic nature. Within the droplets where crystals formed, all crystals manifested as cubic calcite. Higher bacterial density led to the formation of larger and more irregularly shaped crystals, with crystal size showing a significant correlation with urease activity. In droplets where no crystals formed, higher bacterial density and urease activity resulted in the precipitation of amorphous calcium carbonate on the bacterial surface. However, this precipitation pattern differed from the formation of monocrystalline calcium carbonate. The results demonstrate that bacteria act primarily as urease secretors to regulate crystal growth during the MICP process, while their role as nucleation sites for crystals remains debatable. This study provides new insights into the bio-induced calcium carbonate formation mechanism.

Microbially Induced Calcium Carbonate Precipitation UsingLysinibacillussp.: A Ureolytic Bacteriumfrom Uttarakhand for Soil Stabilization.

Microbially induced calcium carbonate precipitation (MICP) is a soil remediation method that has emerged as a viable and long-term solution for enhancing soil mechanical qualities. The technique of MICP that has been extensively researched is urea hydrolysis, which occurs naturally in the environment by urease-producing bacteria as part of their fundamental metabolic processes. The objectives of the current study include screening and identifying native ureolytic bacteria from soil in Uttarakhand, optimizing growth factors for increased urease activity, and calcite precipitation by the bacteria using response surface methodology. Additionally, it was assessed how well the isolated bacteria in the medium biomineralized when using synthetic media and cheaper alternatives such as cow urine and eggshell as sources of urea and Ca2+, respectively. The isolated strain identified as Lysinibacillus sp. was found to be the very active strain after soil samples were screened for ureolytic bacteria. It was discovered that optimization studies with values of pH 8, urea concentration (0.8M), inoculum concentration (3%), and incubation time (48h) yielded a higher activity of 33.7 U/mL (threefold increase), and a higher calcium carbonate precipitation (enzyme activity: 10.96 U/mL, pH: 8.92, soluble Ca2⁺: 25.53mM and insoluble Ca2⁺: 0.856g). The calcite precipitation in broth media supplemented with ready-made substrates and alternative sources demonstrated a similar result of increased pH and ammonia release. Thus, the current study successfully paves the way for several possibilities to stabilize the slopy soils prone to landslides and erosion in Uttarakhand and pinpoint an economic approach through biomineralization.

Regulating the Process of Microbially Induced Calcium Carbonate Precipitation through Applied Electric Fields: Evidence and Insights Using Microfluidics

Regulating the Process of Microbially Induced Calcium Carbonate Precipitation through Applied Electric Fields: Evidence and Insights Using Microfluidics

MICP treated sand: insights into the impact of particle size on mechanical parameters and pore network after biocementation

Microbiologically Induced Calcium Carbonate Precipitation (MICP) is a technology for improving soil characteristics, especially strength, that has been gaining increasing interest in literature during the last few years. Although a lot of influencing factors on the result of MICP are known, particle size and shape of the particles remain poorly understood. While destructive measuring of compressive strength or calcium carbonate content are important for the characterization of samples these methods give no insight into the internal structures and pore networks of the samples. X-ray microcomputed tomography (micro-CT) is a technique that is used to characterize the internals of rocks and to a certain degree MICP-treated soils. However, the impact of filtering and image processing of micro-CT Data depending on the type of MICP sample is poorly described in the literature. In this study, single fractions of local quarry were treated with MICP through the ureolytic microorganism Sporosarcina pasteurii to investigate the influence of particle size distribution on calcium carbonate content, unconfined compressive strength and the reduction of water permeability. Additionally, micro-CT was conducted to obtain insights into the resulting pore system. The impact of the Gauss filter und Non-local means filter on the resulting images and data on the pore network are discussed. The results show that particle size has a significant impact on the result of all tested parameters of biosandstone with lower particle size leading to higher strength and generally higher calcium carbonate content. Micro-CT data showed that the technology is feasible to gain valuable insights into the internal structures of biosandstone but the resolution and signal-to-noise ratio remain challenging, especially for samples with particle sizes smaller than 125 µm.