Interaction of Ca2+ and Fe3+ in co-precipitation process induced by Virgibacillus dokdonensis and its application.

Biomineralization has garnered significant attention in the field of wastewater treatment due to its notable cost reduction compared to conventional methods. The reinjection water from oilfields containing an exceedingly high concentration of calcium and ferric ions will pose a major hazard in production. However, the utilization of biomineralization for precipitating these ions has been scarcely investigated due to limited tolerance among halophiles towards such extreme conditions. In this study, free and immobilized halophiles Virgibacillus dokdonensis were used to precipitate these ions and the effects were compared, at the same time, biomineralization mechanisms and mineral characteristics were further explored. The results show that bacterial concentration and carbonic anhydrase activity were higher when additionally adding ferric ion based on calcium ion; the content of protein, polysaccharides, deoxyribonucleic acid and humic substances in the extracellular polymers also increased compared to control. Calcium ions were biomineralized into calcite and vaterite with multiple morphology. Due to iron doping, the crystallinity and thermal stability of calcium carbonate decreased, the content of OC = O, NC = O and CO-PO3 increased, the stable carbon isotope values became much more negative, and ß-sheet in minerals disappeared. Higher calcium concentrations facilitated ferric ion precipitation, while ferric ions hindered calcium precipitation. The immobilized bacteria performed better in ferric ion removal, with a precipitation ratio exceeding 90%. Free bacteria performed better in calcium removal, and the precipitation ratio reached a maximum of 56%. This research maybe provides some reference for the co-removal of calcium and ferric ions from the oilfield wastewater.

Ectopic Activation of Fgf8 in Dental Mesenchyme Causes Incisor Agenesis and Molar Microdontia.

Putatively, tooth agenesis was attributed to the initiation failure of tooth germs, though little is known about the histological and molecular alterations. To address if constitutively active FGF signaling is associated with tooth agenesis, we activated Fgf8 in dental mesenchyme with Osr-cre knock-in allele in mice (Osr2-creKI; Rosa26R-Fgf8) and found incisor agenesis and molar microdontia. The cell survival assay showed tremendous apoptosis in both the Osr2-creKI; Rosa26R-Fgf8 incisor epithelium and mesenchyme, which initiated incisor regression from cap stage. In situ hybridization displayed vanished Shh transcription, and immunostaining exhibited reduced Runx2 expression and enlarged mesenchymal Lef1 domain in Osr2-creKI; Rosa26R-Fgf8 incisors, both of which were suggested to enhance apoptosis. In contrast, Osr2-creKI; Rosa26R-Fgf8 molar germs displayed mildly suppressed Shh transcription, and the increased expression of Ectodin, Runx2 and Lef1. Although mildly smaller than WT controls prenatally, the Osr2-creKI; Rosa26R-Fgf8 molar germs produced a miniature tooth with impaired mineralization after a 6-week sub-renal culture. Intriguingly, the implanted Osr2-creKI; Rosa26R-Fgf8 molar germs exhibited delayed odontoblast differentiation and accelerated ameloblast maturation. Collectively, the ectopically activated Fgf8 in dental mesenchyme caused incisor agenesis by triggering incisor regression and postnatal molar microdontia. Our findings reported tooth agenesis resulting from the regression from the early bell stage and implicated a correlation between tooth agenesis and microdontia.

"Abraxane-Like" Radiosensitizer for In Situ Oral Cancer Therapy.

Radiotherapy plays a vital role in cancer therapy. However, the hypoxic microenvironment of tumors greatly limits the effectiveness, thus it is crucial to develop a simple, efficient, and safe radiosensitizer to reverse hypoxia and ameliorate the efficacy of radiotherapy. Inspired by the structure of canonical nanodrug Abraxane, herein, a native HSA-modified CaO2 nanoparticle system (CaO2-HSA) prepared by biomineralization-induced self-assembly is developed. CaO2-HSA will accumulate in tumor tissue and decompose to produce oxygen, altering the hypoxic condition inside the tumor. Simultaneously, ROS and calcium ions will lead to calcium overload and further trigger immunogenic cell death. Notably, its sensitizing enhancement ratio (SER = 3.47) is much higher than that of sodium glycididazole used in the clinic. Furthermore, in animal models of in situ oral cancer, CaO2-HSA can effectively inhibit tumor growth. With its high efficacy, facile preparation, and heavy-metal free biosafety, the CaO2-HSA-based radiosensitizer holds enormous potential for oral cancer therapy.

Recombinant human enamelin produced in Escherichia coli promotes mineralization in vitro.

BACKGROUND: Enamelin is an enamel matrix protein that plays an essential role in the formation of enamel, the most mineralized tissue in the human body. Previous studies using animal models and proteins from natural sources point to a key role of enamelin in promoting mineralization events during enamel formation. However, natural sources of enamelin are scarce and with the current study we therefore aimed to establish a simple microbial production method for recombinant human enamelin to support its use as a mineralization agent. RESULTS: In the study the 32 kDa fragment of human enamelin was successfully expressed in Escherichia coli and could be obtained using immobilized metal ion affinity chromatography purification (IMAC), dialysis, and lyophilization. This workflow resulted in a yield of approximately 10 mg enamelin per liter culture. Optimal conditions for IMAC purification were obtained using Ni2+ as the metal ion, and when including 30 mM imidazole during binding and washing steps. Furthermore, in vitro mineralization assays demonstrated that the recombinant enamelin could promote calcium phosphate mineralization at a concentration of 0.5 mg/ml. CONCLUSIONS: These findings address the scarcity of enamelin by facilitating its accessibility for further investigations into the mechanism of enamel formation and open new avenues for developing enamel-inspired mineralized biomaterials.

Modified five times simulated body fluid for efficient biomimetic mineralization.

Simulated body fluid (SBF) is widely utilized in preclinical research for estimating the mineralization efficacy of biomaterials. Therefore, it is of great significance to construct an efficient and stable SBF mineralization system. The conventional SBF solutions cannot maintain a stable pH value and are prone to precipitate homogeneous calcium salts at the early stages of the biomimetic process because of the release of gaseous CO2. In this study, a simple but efficient five times SBF buffered by 5 % CO2 was developed and demonstrated to achieve excellent mineralized microstructure on a type of polymer-aligned nanofibrous scaffolds, which is strikingly similar to the natural human bone tissue. Scanning electron microscopy and energy-dispersive X-ray examinations indicated the growth of heterogeneous apatite with a high-calcium-to-phosphate ratio on the aligned nanofibers under 5 times SBF buffered by 5 % CO2. Moreover, X-ray diffraction spectroscopy and Fourier transform infrared analyses yielded peaks associated with carbonated hydroxyapatite with less prominent crystallization. In addition, the biomineralized aligned polycaprolactone nanofibers demonstrated excellent cell attachment, alignment, and proliferation characteristics in vitro. Overall, the results of this study showed that 5 × SBFs buffered by 5 % CO2 partial pressure are attractive alternatives for the efficient biomineralization of scaffolds in bone tissue engineering, and could be used as a model for the prediction of the bone-bonding bioactivity of biomaterials.

Mimicking nature to develop halide perovskite semiconductors from proteins and metal carbonates.

Halide perovskite (HPs) nanostructures have recently gained extensive worldwide attentions because of their remarkable optoelectronic properties and fast developments. However, intrinsic instability against environmental factors-i.e., temperature, humidity, illumination, and oxygen-restricted their real-life applications. HPs are typically synthesized as colloids by employing organic solvents and ligands. Consequently, the precise control and tuning of complex 3D perovskite morphologies are challenging and have hardly been achieved by conventional fabrication methods. Here, we combine the benefits of self-assembly of biomolecules and an ion exchange reaction (IER) approach to customize HPs spatial shapes and composition. Initially, we apply a biomineralization approach, using biological templates (such as biopolymers, proteins, or protein assemblies), modulating the morphology of MCO3 (M = Ca2+, Ba2+) nano/microstructures. We then show that the morphology of the materials can be maintained throughout an IER process to form surface HPs with a wide variety of morphologies. The fabricated core-shell structures of metal carbonates and HPs introduce nano/microcomposites that can be sculpted into a wide diversity of 3D architectures suitable for various potential applications such as sensors, detectors, catalysis, etc. As a prototype, we fabricate disposable humidity sensors with an 11-95% detection range by casting the formed bio-templated nano/micro-composites on paper substrate.

A bioinspired doxorubicin-carried albumin Nanocage against aggressive Cancer via systemic targeting of tumor and lymph node metastasis.

Cancer metastasis and recurrence are obstacles to successful treatment of aggressive cancer. To address this challenge, chemotherapy is indispensable as an essential part of comprehensive cancer treatment, particularly for subsequent therapy after surgical resection. However, small-molecule drugs for chemotherapy always cause inadequate efficacy and severe side effects against cancer metastasis and recurrence caused by lymph node metastases. Here, we developed doxorubicin-carried albumin nanocages (Dox-AlbCages) with appropriate particle sizes and pH/enzyme-responsive drug release for tumor and lymph node dual-targeted therapy by exploiting the inborn transport properties of serum albumin. Inspired by the protein-templated biomineralization and remote loading of doxorubicin into liposomes, we demonstrated the controlled synthesis of Dox-AlbCages via the aggregation or crystallization of doxorubicin and ammonium sulfate within albumin nanocages using a biomineralization strategy. Dox-AlbCages allowed efficient encapsulation of Dox in the core protected by the albumin corona shell, exhibiting favorable properties for enhanced tumor and lymph node accumulation and preferable cellular uptake for tumor-specific chemotherapy. Intriguingly, Dox-AlbCages effectively inhibited tumor growth and metastasis in orthotopic 4T1 breast tumors and prevented postsurgical tumor recurrence and lung metastasis. At the same time, Dox-AlbCages had fewer side effects than free Dox. This nanoplatform provides a facile strategy for designing tumor- and lymph node-targeted nanomedicines for suppressing cancer metastasis and recurrence.

Deciphering the molecular toolkit: regulatory elements governing shell biomineralization in marine molluscs.

The intricate process of shell biomineralization in marine molluscs is governed by a complex interplay of regulatory elements, encompassing secretomes, transporters, and noncoding RNA. This review delves into recent advancements in understanding these regulatory mechanisms, emphasizing their significance in elucidating the functions and evolutionary dynamics of the molluscan shell biomineralization process. Central to this intricate orchestration are secretomes with diverse functional domains, selectively exported to the extrapallial space, which directly regulate crystal growth and morphology. Transporters are crucial for substrate transportation in the calcification and maintenance of cellular homeostasis. Beyond proteins and transporters, noncoding RNA molecules are integral components influencing shell biomineralization. This review underscores the nonnegligible roles played by these genetic elements at the molecular level. To comprehend the complexity of biomineralization in mollusc, we explore the origin and evolutionary history of regulatory elements, primarily secretomes. While some elements have recently evolved, others are ancient genes that have been co-opted into the biomineralization toolkit. These elements undergo structural and functional evolution through rapidly evolving repetitive low-complexity domains and domain gain/loss/rearrangements, ultimately shaping a distinctive set of secretomes characterized by both conserved features and evolutionary innovations. This comprehensive review enhances our understanding of molluscan biomineralization at the molecular and genetic levels.

Advances in microbial self-healing concrete: A critical review of mechanisms, developments, and future directions.

The self-healing bioconcrete, or bioconcrete as concrete containing microorganisms with self-healing capacities, presents a transformative strategy to extend the service life of concrete structures. This technology harnesses the biological capabilities of specific microorganisms, such as bacteria and fungi, which are integral to the material's capacity to autonomously mend cracks, thereby maintaining structural integrity. This review highlights the complex biochemical pathways these organisms utilize to produce healing compounds like calcium carbonate, and how environmental parameters, such as pH, temperature, oxygen, and moisture critically affect the repair efficacy. A comprehensive analysis of recently published peer-reviewed literature, and contemporary experimental research forms the backbone of this review with a focus on microbiological aspects of the self-healing process. The review assesses the challenges facing self-healing bioconcrete, including the longevity of microbial spores and the cost implications for large-scale implementation. Further, attention is given to potential research directions, such as investigating alternative biological agents and optimizing the concrete environment to support microbial activity. The culmination of this investigation is a call to action for integrating self-healing bioconcrete in construction on a broader scale, thereby realizing its potential to fortify infrastructure resilience and sustainability.

Phosphorus recovery and tetracycline Mitigation: The role of Bacillus cereus LB-9 in struvite biomineralization from wastewater.

Struvite biomineralization is an ecologically sound technology, adept at the efficient recovery and recycling of phosphorus from wastewater. However, the biomineralization process is often perturbed by the presence of antibiotics, notably tetracycline (TC), the impact of which on the biomineralization system has not been elucidated. This study examines the efficacy of Bacillus cereus LB-9 in struvite biomineralization, focusing on the precipitates' composition, morphology, and TC content. LB-9 facilitate an alkaline environment that effectively recovering nitrogen and phosphorus. These findings indicate that TC retards the initial formation of struvite and the concurrent recovery of nitrogen and phosphorus. However, at concentrations below 10 mg/L TC concentrations, TC enhanced struvite production (0.38g) by stimulating LB-9's growth and metabolic activity. Conversely, at a concentration of 10 mg/L TC, the strain's activity was markedly suppressed within the initial four days. This data suggests that TC promotes the strain's proliferation and metabolism, potentially through cellular secretions, thereby augmenting phosphorus recovery from wastewater. Notably, the recovered struvite doesn't contain TC, aligning with regulatory standards for agricultural application. In summary, LB-9-mediated struvite recovery is an effective strategy for producing phosphorus-enriched fertilizers and mitigating TC contamination, offering significant implications for wastewater treatment and industrial process development, particularly in the context of prevalent TC in wastewater.

Sulfide-carbonate-mineralized functional bacterial consortium for cadmium removal in flue gas.

Sulfide-carbonate-mineralized functional bacterial consortium was constructed for flue gas cadmium biomineralization. A membrane biofilm reactor (MBfR) using the bacterial consortium containing sulfate reducing bacteria (SRB) and denitrifying bacteria (DNB) was investigated for flue gas cadmium (Cd) removal. Cadmium removal efficiency achieved 90%. The bacterial consortium containing Citrobacter, Desulfocurvus and Stappia were dominated for cadmium resistance-nitrate-sulfate reduction. Under flue gas cadmium stress, ten cadmium resistance genes (czcA, czcB, czcC, czcD, cadA, cadB, cadC, cueR, copZ, zntA), and seven genes related to sulfate reduction, increased in abundance; whereas others, nine genes related to denitrification, decreased, indicating that cadmium stress was advantageous to sulfate reduction in the competition with denitrification. A bacterial consortium could capable of simultaneously cadmium resistance, sulfate reduction and denitrification. Microbial induced carbonate precipitation (MICP) and biological adsorption process would gradually yield to sulfide-mineralized process. Flue gas cadmium could transform to Cd-EPS, cadmium carbonate (CdCO3) and cadmium sulfide (CdS) bioprecipitate. The functional bacterial consortium was an efficient and eco-friendly bifunctional bacterial consortium for sulfide-carbonate-mineralized of cadmium. This provides a green and low-carbon advanced treatment technology using sulfide-carbonate-mineralized functional bacterial consortium for the removal of cadmium or other hazardous heavy metal contaminants in flue gas.

Nanocoated bacteria with H2S generation-triggered self-amplified photothermal and photodynamic effect for breast cancer therapy.

Phototherapy utilizing bacterial carriers has demonstrated efficacy in anti-tumor therapy, while the poor delivery of phototherapeutic agents and immunogenicity of microbial substances remain problematic. Herein, we develop a nanocoated bacterial delivery system (IF-S.T) that in situ forms the efficient photothermal agents via biomineralization and improves the intracellular oxygenation, thus triggering the self-enhanced photothermal therapy (PTT) and photodynamic therapy (PDT) on tumor. We densely coat self-assembled IF (ICGFe2+) nanocomplex onto the surface of LT2, a virulent strain of Salmonella typhimurium (S.T), by bioadaptive nanocoating techniques, masking bacterial virulence factors and reducing the potential immune adverse effects. Upon penetrating into the tumor environment, IF-S.T responds to H2O2 to trigger the removal of the IF coating, where S.T produces excess hydrogen sulfide (H2S). H2S reacts with Fe2+, yielding ferrous sulfide (FeS) for PTT, and inhibits mitochondrial respiration to enhance tumor cell oxygenation for PDT. Consequently, IF-S.T plus laser irradiation exhibits direct tumor cells killing and elicits robust antitumor immune responses, leading to the complete tumor elimination. Thus, IF-S.T represents a promising platform for effective tumor delivery of photoactive agents for improved PTT/PDT efficacy.

Efficient uranium sequestration ability and mechanism of live and inactivated strain of Streptomyces sp. HX-1 isolated from uranium wastewater.

Prokaryotes are effective biosorbents for the recovery of uranium and other heavy metals. However, the potential mechanism of uranium bioaccumulation by filamentous strain (actinobacteria) remains unclear. This study demonstrates the potential for and mechanism of uranium bioaccumulation by living (L-SS) and inactivated (I-SS) Streptomyces sp. HX-1 isolated from uranium mine waste streams. Uranium accumulation experiments showed that L-SS and I-SS had efficient uranium adsorption potentials, with removal rates of 92.93 and 97.42%, respectively. Kinetic and equilibrium data indicated that the bioaccumulation process was consistent with the pseudo-second-order kinetic, Langmuir, and Sips isotherm models. FTIR indicated that the main functional groups of L-SS and I-SS binding uranium were uranyl, carboxyl, and phosphate groups. Moreover, the results of XRD, XPS, SEM-EDS, and TEM-EDS analyses revealed for the first time that L-SS has biomineralization and bioreduction capacity against uranium. L-SS mineralize U(VI) into NH4UO2PO4 and [Formula: see text] through the metabolic activity of biological enzymes (phosphatases). In summary, Streptomyces sp. HX-1 is a novel and efficient uranium-fixing biosorbent for the treatment of uranium-contaminated wastewater.

Biomineralization for Reducing and Controlling Sand-Dust Storms.

The sand-dust weather and sand-dust storms have become a serious environmental disaster worldwide. It is an important challenge to develop technologies for desert sand solidification in order to prevent and control sand-dust weather. The biomineralization technology for solidifying desert sands has been a novel method for reinforced soils in recent years. The biomineralization solidification sand field tests are completed at the Wuma Highway solidification section in the Tengger Desert. The superiority of the biomineralization for solidifying sands is verified by measuring the water storage capacity of different reinforcement zones including bare sand zone, plant zone, biomineralization solidifying sand zone, and biomineralization combined plant solidifying sand zone. Simultaneously, the molecular dynamics calculation analysis is used to verify the role of biomineralization solidifying sands in preventing sand-dust storms. All results demonstrate that the biomineralization solidification sand method is effective for controlling and preventing sandstorm disasters.

Mechanistic insights into tris(2-chloroisopropyl) phosphate biomineralization coupled with lead (II) biostabilization driven by denitrifying bacteria.

The ubiquity and persistence of organophosphate esters (OPEs) and heavy metal (HMs) pose global environmental risks. This study explored tris(2-chloroisopropyl)phosphate (TCPP) biomineralization coupled to lead (Pb2+) biostabilization driven by denitrifying bacteria (DNB). The domesticated DNB achieved synergistic bioremoval of TCPP and Pb2+ in the batch bioreactor (efficiency: 98 %).TCPP mineralized into PO43- and Cl-, and Pb2+ precipitated with PO43-. The TCPP-degrading/Pb2+-resistant DNB: Achromobacter, Pseudomonas, Citrobacter, and Stenotrophomonas, dominated the bacterial community, and synergized TCPP biomineralization and Pb2+ biostabilization. Metagenomics and metaproteomics revealed TCPP underwent dechlorination, hydrolysis, the TCA cycle-based dissimilation, and assimilation; Pb2+ was detoxified via bioprecipitation, bacterial membrane biosorption, EPS biocomplexation, and efflux out of cells. TCPP, as an initial donor, along with NO3-, as the terminal acceptor, formed a respiratory redox as the primary energy metabolism. Both TCPP and Pb2+ can stimulate phosphatase expression, which established the mutual enhancements between their bioconversions by catalyzing TCPP dephosphorylation and facilitating Pb2+ bioprecipitation. TCPP may alleviate the Pb2+-induced oxidative stress by aiding protein phosphorylation. 80 % of Pb2+ converted into crystalized pyromorphite. These results provide the mechanistic foundations and help develop greener strategies for synergistic bioremediation of OPEs and HMs.

New Avenues for Capturing Mineralization Events at Biomaterial Interfaces with Liquid-Transmission Electron Microscopy.

Liquid-transmission electron microscopy (liquid-TEM) provides exciting potential for capturing mineralization events at biomaterial interfaces, though it is largely unexplored. To address this, we established a unique approach to visualize calcium phosphate (CaP)-titanium (Ti) interfacial mineralization events by combining the nanofabrication of Ti lamellae by focused ion beam with in situ liquid-TEM. Multiphasic CaP particles were observed to nucleate, adhere, and form different assemblies onto and adjacent to Ti lamellae. Here, we discuss new approaches for exploring the interaction between biomaterials and liquids at the nanoscale. Driving this technology is crucial for understanding and controlling biomineralization to improve implant osseointegration and direct new pathways for mineralized tissue disease treatment in the future.

Biological Surface Layer Formation on Bioceramic Particles for Protein Adsorption.

In the biomedical fields of bone regenerative therapy, the immobilization of proteins on the bioceramic particles to maintain their highly ordered structures is significantly important. In this review, we comprehensively discussed the importance of the specific surface layer, which can be called "non-apatitic layer", affecting the immobilization of proteins on particles such as hydroxyapatite and amorphous silica. It was suggested that the water molecules and ions contained in the non-apatitic layer can determine and control the protein immobilization states. In amorphous silica particles, the direct interactions between proteins and silanol groups make it difficult to immobilize the proteins and maintain their highly ordered structures. Thus, the importance of the formation of a surface layer consisting of water molecules and ions (i.e., a non-apatitic layer) on the particle surfaces for immobilizing proteins and maintaining their highly ordered structures was suggested and described. In particular, chlorine-containing amorphous silica particles were also described, which can effectively form the surface layer of protein immobilization carriers. The design of the bio-interactive and bio-compatible surfaces for protein immobilization while maintaining the highly ordered structures will improve cell adhesion and tissue formation, thereby contributing to the construction of social infrastructures to support super-aged society.

Carbonate precipitation and phosphate trapping by microbialite isolates from an alkaline insular lake (Bagno dell'Acqua, Pantelleria Island, Italy).

The Bagno dell'Acqua lake is characterized by CO2 emissions, alkaline waters (pH = 9) and Eh values which indicate strongly oxidizing conditions. A typical feature of the lake is the presence of actively growing microbialites rich in calcium carbonates and silica precipitates. Mineralogy, petrography and morphology analyses of the microbialites were coupled with the analysis of the microbial community, combining molecular and cultivation approaches. The DNA sequencing revealed distinct patterns of microbial diversity, showing pronounced differences between emerged and submerged microbialite, with the upper layer of emerged samples exhibiting the most distinctive composition, both in terms of prokaryotes and eukaryotes. In particular, the most representative phyla in the microbial community were Proteobacteria, Actinobacteriota, and Bacteroidota, while Cyanobacteria were present only with an average of 5%, with the highest concentration in the submerged intermediate layer (12%). The role of microorganisms in carbonate mineral formation was clearly demonstrated as most of the isolates were able to precipitate calcium carbonate and five of them were characterized at molecular level. Interestingly, when microbial isolates were cultivated only in filtered water, the precipitation of hazenite was observed (up to 85%), opening new prospective in P (phosphate) recovery from P depleted environments.

Amyloid and collagen templates in aortic valve calcification.

Calcific aortic valve disease (CAVD) is a widely prevalent heart disorder in need of pharmacological interventions. Calcified areas in aortic valves often contain amyloid fibrils that promote calcification in vitro. This opinion paper suggests that amyloid contributes to CAVD development; amyloid-assisted nucleation can accelerate hydroxyapatite deposition onto collagen matrix. Notably, acidic arrays in amyloid match calcium-calcium spacing in the amorphous hydroxyapatite precursor, while oscillating hemodynamic perturbations promote amyloid deposition in the valve. Lipoprotein(a), a genetic risk factor for CAVD, augments calcification via several mechanisms, wherein hydrolysis of oxidized phospholipids (oxPLs) by Lp(a)-associated enzymes helps generate orthophosphate, and apolipoprotein(a) blocks plasmin-induced fibril degradation. Current studies of amyloid-calcium-collagen interactions in solution and in fibrillar complexes allow deeper insight into the role of amyloid in calcification.

Impact of soil density on biomineralization using EICP and MICP techniques for earthen sites consolidation.

Enzyme-induced calcium carbonate precipitation (EICP) and microbially-induced calcium carbonate precipitation (MICP) techniques represent emerging trends in soil stabilization. However, the impact of soil density on biomineralization, particularly in historical earthen sites, remains unclear. This study compares the consolidation effects of EICP and MICP on cylindrical samples (10 cm × 5 cm) with three densities (1.5 g/cm3, 1.6 g/cm3, and 1.7 g/cm3) derived from the soil near the UNESCO World Cultural Heritage Site of Suoyang Ancient City, Gansu Province, China. Results showed that calcium carbonate production increased across all densities through bio-cementation, with higher densities producing more calcium carbonate. MICP-treated specimens exhibited larger increases in calcium carbonate production compared to those treated with EICP. Specimens with a density of 1.7 g/cm³ showed a wave velocity increase of 3.26% (EICP) and 7.13% (MICP), and an unconfined compressive strength increase of 8% (EICP) and 26% (MICP). These strength increases correlated with the generation of calcium carbonate. The findings suggest that biomineralization can be effectively utilized for in situ consolidation of earthen sites, emphasizing the importance of considering soil density in biologically-based conservation technologies. Furthermore, MICP shows potential advantages over EICP in providing stronger, compatible and more sustainable soil reinforcement.