Ecofriendly solidification of sand using microbially induced calcium phosphate precipitation.

This study introduces microbiologically induced calcium phosphate precipitation (MICPP) as a novel and environmentally sustainable method of soil stabilization. Using Limosilactobacillus sp., especially NBRC 14511 and fish bone solution (FBS) extracted from Tuna fish bones, the study was aimed at testing the feasibility of calcium phosphate compounds (CPCs) deposition and sand stabilization. Dynamic changes in pH and calcium ion (Ca2+) concentration during the precipitation experiments affected the precipitation and sequential conversion of dicalcium phosphate dihydrate (DCPD) to hydroxyapatite (HAp), which was confirmed by XRD and SEM analysis. Sand solidification experiments demonstrated improvements in unconfined compressive strength (UCS), especially at higher Urea/Ca2+ ratios. The UCS values obtained were 10.35 MPa at a ratio of 2.0, 3.34 MPa at a ratio of 1.0, and 0.43 MPa at a ratio of 0.5, highlighting the advantages of MICPP over traditional methods. Microstructural analysis further clarified the mineral composition, demonstrating the potential of MICPP in environmentally friendly soil engineering. The study highlights the promise of MICPP for sustainable soil stabilization, offering improved mechanical properties and reducing environmental impact, paving the way for novel geotechnical practices.

Eco-friendly soil stabilization method using fish bone as cement material.

The method of soil improvement by calcium phosphate precipitation is a novel, environmentally friendly, and non-toxic technique. Such technology provides advantages over ureolytic induced calcite precipitation (UICP), the most popular and widely used method in the field of geotechnical engineering. In this paper, an investigation of the consolidation of fine and coarse sand samples by enzyme induced calcium phosphate precipitation (EICPP) was carried out. Tuna bones were used as an alternative source of calcium and phosphorus ions, as one of the most popular fish species in Japan and the main source of food industry waste. Unconfined compressive strength (UCS) of the samples after 21 days of daily injection of the solution showed an increase in strength up to 6,05 MPa in fine and up to 4,3 MPa in coarse sand samples. X-ray powder diffraction (XRD), scanning electron microscope (SEM), and energy dispersive X-ray spectroscopy (SEM-EDS) analysis were performed to investigate the nature and type of deposition. Analyses confirmed that deposition is composed of brushite with needle-like crystals in the case of Toyoura sand and flower-like crystals in the case of Mikawa sand. SEM-EDS showed a presence of both, calcium, and phosphorus in the precipitate, indicating the presence of calcium phosphate compounds (CPCs). This study reveals that tuna bones are a rich source of calcium and phosphorus for EICPP, which results in a strengthening of silicate soil up to 3.4-6.05 MPa and is able to reduce ammonia emissions by 85.7 % - 97.5 % compared to UICP.

Baseline investigation on soil solidification through biocementation using airborne bacteria.

Microbial induced carbonate precipitation (MICP) through the ureolysis metabolic pathway is one of the most studied topics in biocementation due to its high efficiency. Although excellent outcomes have proved the potential of this technique, microorganisms face some obstacles when considering complicated situations in the real field, such as bacterial adaptability and survivability issues. This study made the first attempt to seek solutions to this issue from the air, exploring ureolytic airborne bacteria with resilient features to find a solution to survivability issues. Samples were collected using an air sampler in Sapporo, Hokkaido, a cold region where sampling sites were mostly covered with dense vegetation. After two rounds of screening, 12 out of 57 urease-positive isolates were identified through 16S rRNA gene analysis. Four potentially selected strains were then evaluated in terms of growth pattern and activity changes within a range of temperatures (15°C-35°C). The results from sand solidification tests using two Lederbergia strains with the best performance among the isolates showed an improvement in unconfined compressive strength up to 4-8 MPa after treatment, indicating a high MICP efficiency. Overall, this baseline study demonstrated that the air could be an ideal isolation source for ureolytic bacteria and laid a new pathway for MICP applications. More investigations on the performance of airborne bacteria under changeable environments may be required to further examine their survivability and adaptability.

Functional modification of mussel adhesive protein to control solubility and adhesion property.

Marine mussels produce strong underwater adhesives called mussel adhesive proteins (MAPs) that can adhere to a variety of surfaces under physiological conditions. Thus, MAPs have been investigated as a potentially sustainable alternative to conventional petrochemical-based adhesives. Recombinant MAPs would be promising for large-scale production and commercialization; however, MAPs are intrinsically adhesive, aggregative, and insoluble in water. In this study, we have developed a solubilization method for the control of MAP adhesion by fusion protein technique. Foot protein 1 (Fp1), a kind of MAP, was fused with the highly water-soluble protein, which is the C-terminal domain of ice-nucleation protein K (InaKC), separated by a protease cleaving site. The fusion protein exhibited low adhesion but high solubility and stability. Notably, Fp1 recovered its adhesive property after removal from the InaKC moiety by protease cleaving, which was evaluated and confirmed by the agglomeration of magnetite particles in water. The ability to control adhesion and agglomeration makes MAPs favorable prospects for bio-based adhesives.

Interfacial biosilica coating of chitosan gel using fusion silicatein to fabricate robust hybrid material for biomolecular applications.

An enzyme-encapsulated silica-based hybrid material was developed using a chitosan gel. Fusion silicatein (InaKC-ChBD-Sil), silicatein fused with a soluble tag and chitin-binding domain, was employed as an interfacial catalyst to form silica on a chitosan gel matrix under physiological conditions, and horseradish peroxidase was immobilised on the hybrid material. Silica formation on the gel was verified via fluorescence microscopy using a designed fusion protein called TBP-mCherry, a fluorescent protein fused with a silica-binding peptide. We report a chitosan gel-silica hybrid material capable of encapsulating enzymes for biomedical and environmental applications.

Naturally Derived Cements Learned from the Wisdom of Ancestors: A Literature Review Based on the Experiences of Ancient China, India and Rome.

For over a thousand years, many ancient cements have remained durable despite long-term exposure to atmospheric or humid agents. This review paper summarizes technologies of worldwide ancient architectures which have shown remarkable durability that has preserved them over thousands of years of constant erosion. We aim to identify the influence of organic and inorganic additions in altering cement properties and take these lost and forgotten technologies to the production frontline. The types of additions were usually decided based on the local environment and purpose of the structure. The ancient Romans built magnificent structures by making hydraulic cement using volcanic ash. The ancient Chinese introduced sticky rice and other local materials to improve the properties of pure lime cement. A variety of organic and inorganic additions used in traditional lime cement not only changes its properties but also improves its durability for centuries. The benefits they bring to cement may also be useful in enzyme-induced carbonate precipitation (EICP) and microbially induced carbonate precipitation (MICP) fields. For instance, sticky rice has been confirmed to play a crucial role in regulating calcite crystal growth and providing interior hydrophobic conditions, which contribute to improving the strength and durability of EICP- and MICP-treated samples in a sustainable way.

Influence of humic acid on microbial induced carbonate precipitation for organic soil improvement.

Microbial induced carbonate precipitation (MICP) is one of the most commonly researched topics on biocementation, which achieves cementation of soil particles by carbonate from urea hydrolysis catalyzed by microbial urease. Although most MICP studies are limited to stabilizing sandy soils, more researchers are now turning their interest to other weak soils, particularly organic soils. To stabilize organic soils, the influence of humic substances should be investigated since it has been reported to inhibit urease activity and disrupt the formation of calcium carbonate. This study investigates the effect of humic acid (HA), one fraction of humic substances, on MICP. For this purpose, the effects of HA content on CaCO3 precipitation using three strains and on CaCO3 morphology were examined. The results showed that native species in organic soils were less adversely affected by HA addition than the exogenous one. Another interesting finding is that bacteria seem to have strategies to cope with harsh conditions with HA. Observation of CaCO3 morphology revealed that the crystallization process was hindered by HA to some extent, producing lots of fine amorphous precipitates and large aggregated CaCO3. Overall, this study could provide an insightful understanding of possible obstacles when using MICP to stabilize organic soils.

State-of-the-Art Review on Engineering Uses of Calcium Phosphate Compounds: An Eco-Friendly Approach for Soil Improvement.

Greenhouse gas emissions are a critical problem nowadays. The cement manufacturing sector alone accounts for 8% of all human-generated emissions, and as the world's population grows and globalization intensifies, this sector will require significantly more resources. In order to fulfill the need of geomaterials for construction and to reduce carbon dioxide emissions into the atmosphere, conventional approaches to soil reinforcement need to be reconsidered. Calcium phosphate compounds (CPCs) are new materials that have only recently found their place in the soil reinforcement field. Its eco-friendly, non-toxic, reaction pathway is highly dependent on the pH of the medium and the concentration of components inside the solution. CPCs has advantages over the two most common environmental methods of soil reinforcement, microbial-induced carbonate precipitation (MICP) and enzyme induced carbonate precipitation (EICP); with CPCs, the ammonium problem can be neutralized and thus allowed to be applied in the field. In this review paper, the advantages and disadvantages of the engineering uses of CPCs for soil improvement have been discussed. Additionally, the process of how CPCs perform has been studied and an analysis of existing studies related to soil reinforcement by CPC implementation was conducted.

Valorization of tannery solid wastes for sustainable enzyme induced carbonate precipitation process.

Biocementation via enzyme induced carbonate precipitation (EICP) is an emerging ground improvement technique that utilizes urease for calcium carbonate precipitation. Usage of expensive laboratory grade chemicals in EICP hinders its implementation at field level applications. In this study, the feasibility of utilizing solid wastes generated from leather industry was investigated for EICP process. Initially, the proteinaceous fleshing waste was used as nitrogen source for production of an extracellular urease from Arthrobacter creatinolyticus MTCC 5604 followed by its subsequent use in EICP with suspended solids of tannery lime liquor, as alternative calcium source. The calcium ion solution was prepared by treating suspended solids of lime liquor with 1 N HCl. The EICP was optimum with 1000 U of urease, 1.0 M urea and 1.0 M CaCl2.2H2O for test tube experiments. Sand solidification experiments under optimal conditions with five times addition of cementation solution yielded a maximum unconfined compressive strength (UCS) of 810 kPa with laboratory grade CaCl2.2H2O and 780 kPa with calcium from lime liquor. The crystalline phases and morphology of the CaCO3 precipitate were analyzed by XRD, FTIR and SEM-EDX. The results showed the formation of more stable calcite in EICP with calcium obtained from lime liquor, while calcite and vaterite polymorphs were obtained with CaCl2.2H2O. Utilization of fleshing waste and lime liquor in EICP could reduce the pollution load and sludge formation that are generated during the pre-tanning operations of leather manufacturing. The results indicated the viability of process to achieve cost effective and sustainable biocementation for large scale applications.

Polymer-assisted enzyme induced carbonate precipitation for non-ammonia emission soil stabilization.

Biocementation using enzyme induced carbonate precipitation (EICP) process has become an innovative method for soil improvement. One of the major limitations in scaling-up of biocement treatment is the emission of gaseous ammonia during the urea hydrolysis, which is environmentally hazardous. In order to eliminate this shortcoming, this paper presents a series of experiments performed to evaluate a novel approach for preventing the ammonia byproducts in the EICP process via the use of polyacrylic acid (PAA). Through the adjustment of the pH to acidic, PAA not only promotes the enzyme activity, but also averts the conversion of ammonium to gaseous ammonia and its release, thus preventing any harm to the environment. The sand samples were treated with cementation solution and assessed for improvement in strength. Calcium carbonate content measurements and X-ray powder diffraction analysis identified the calcite crystals precipitated in the soil pores. Scanning electron microscopy analysis clearly showed that calcium carbonate was precipitated connecting soil particles, thus providing a uniaxial compressive strength (UCS) of up to 1.65 MPa. Overall, the inhibition in the speciation of gaseous ammonia shows the great potential of PAA for large-scale promotion of biocement.

Durability Improvement of Biocemented Sand by Fiber-Reinforced MICP for Coastal Erosion Protection.

Soil improvement via MICP (microbially induced carbonate precipitation) technologies has recently received widespread attention in the geoenvironmental and geotechnical fields. The durability of MICP-treated samples remains a critical concern in this novel method. In this work, fiber (jute)-reinforced MICP-treated samples were investigated to evaluate their durability under exposure to distilled water (DW) and artificial seawater (ASW), so as to advance the understanding of long-term performance mimicking real field conditions, along with improvement of the MICP-treated samples for use in coastal erosion protection. Primarily, the results showed that the addition of fiber (jute) improved the durability of the MICP-treated samples by more than 50%. Results also showed that the wet-dry (WD) cyclic process resulted in adverse effects on the mechanical and physical characteristics of fiber-reinforced MICP-treated samples in both DW and ASW. The breakdown of calcium carbonates and bonding effects in between the sand particles was discovered to be involved in the deterioration of MICP samples caused by WD cycles, and this occurs in two stages. The findings of this study would be extremely beneficial to extend the insight and understanding of improvement and durability responses for significant and effective MICP treatments and/or re-treatments.

Differential diagnosis between calcifying odontogenic cyst and adenomatoid odontogenic tumor by computed tomography images.

OBJECTIVES: Calcifying odontogenic cysts (COC) and adenomatoid odontogenic tumors (AOT) have similar radiographic findings. We examined the radiographic and computed tomography (CT) images of patients histologically diagnosed with COC or AOT and identified their characteristic findings. METHODS: The subjects included 12 patients histologically diagnosed with COC or AOT (one female and five males per group), who underwent CT at our hospital between Nov 1998 and Jun 2019. The location of the lesion, impacted tooth, bone expansion, root resorption, tooth migration, calcified body, and presence or absence of a high-intensity zone in the marginal area of the lesion were examined. RESULTS: In patients with COC, five patients with COC exhibited bone expansion toward the buccal side. The lesion encompassing the crown was attached to the cement-enamel junction and contained a radiopaque lesion with a calcified body. In 6 patients with COC, irregularly shaped calcified bodies were observed with small tooth-like structures. In patients with AOT, all six patients with AOT exhibited bone expansion toward the buccal and lingual sides. The lesion encompasses a part of the tooth root or the entire tooth. Punctate calcification was observed within the lesion and the marginal area in three patients, and a high-intensity zone was observed in the marginal area of the lesion in two patients. CONCLUSION: We report imaging findings that may be characteristic of COC and AOT, suggesting that CT findings may be useful for differentiating between COC and AOT.

Solubilization and aggregation control of silica-polymerizing enzyme fused with a removable soluble protein.

Silicatein, a silica-polymerizing enzyme, is an attractive and promising biocatalyst in many applications such as the synthesis of bio-functionalized inorganic materials under mild conditions. However, its unfavorable aggregation in aqueous media due to its intermolecular hydrophobic interactions causes difficulties in handling and applications. This study aimed to enhance the solubility of silicatein via fusion with a small soluble protein, ProS2. ProS2-Sil showed high solubility and stability in aqueous media for more than 24 h. The aggregation property of ProS2-silicatein fusion protein (ProS2-Sil) was investigated with and without cleavage of ProS2 tag by site-specific protease. When ProS2 tag was removed, silicatein became aggregated, which was analyzed by transmission electron microscope and fluorescence microscope. ProS2-Sil and mature silicatein showed similar activities in silica polymerization. The present approach allows the utilization of silicatein in the fabrication of novel and functional inorganic biohybrid materials.

Experimental Study on Sand Stabilization Using Bio-Cementation with Wastepaper Fiber Integration.

Recently, green materials and technologies have received considerable attention in geotechnical engineering. One of such techniques is microbially-induced carbonate precipitation (MICP). In the MICP process, CaCO3 is achieved bio-chemically within the soil, thus enhancing the strength and stiffness. The purpose of this study is to introduce the wastepaper fiber (WPF) onto the MICP (i) to study the mechanical properties of MICP-treated sand with varying WPF content (0-8%) and (ii) to assess the freeze-thaw (FT) durability of the treated samples. Findings revealed that the ductility of the treated samples increases with the increase in WPF addition, while the highest UCS is found with a small fiber addition. The results of CaCO3 content suggest that the WPF addition enhances the immobilization of the bacteria cells, thus yielding the precipitation content. However, shear wave velocity analysis indicates that a higher addition of WPF results in rapid deterioration of the samples when subjected to freeze-thaw cycles. Microscale analysis illuminates that fiber clusters replace the solid bonding at particle contacts, leading to reduced resistance to freeze-thaw damage. Overall, the study demonstrates that as a waste material, WPF could be sustainably reused in the bio-cementation.

Fabrication of silica on chitin in ambient conditions using silicatein fused with a chitin-binding domain.

High temperatures, harsh pH conditions, and toxic chemicals involved in the conventional synthesis and coating of silica limit the fabrication of new-generation hybrid materials immobilizing live cells and biomolecules such as enzymes and drugs. This hinders the application of inorganic-organic biohybrid materials in various fields, including bioelectronics, energy generation, and biomedicine. Silicatein, an enzyme found in siliceous sponges, catalyzes the polymerization of silica under mild conditions, that is, at room temperature and neutral pH. Silicatein was fused with a chitin-binding domain (ChBD) to selectively bind the fusion silicatein on the chitin material and with a small soluble tag called InakC, a hydrophilic protein from Pseudomonas syringae, to control the unfavorable aggregation of silicatein. The fusion silicatein was soluble in aqueous media and was successfully found to be adsorbed on the chitin material. The immobilized fusion silicatein acted as an interfacial catalyst to fabricate silica on chitin under ambient conditions. This technique can be used to fabricate inorganic-organic hybrid materials to immobilize biomolecules and can be applied to develop novel biocatalytic systems, biosensors, and tissue culture scaffolds.

Applications of chitosan in environmental remediation: A review.

Environmental biotechnology is the use of biotechnology to develop and regulate biological systems for the remediation of environmental contamination. Nature has gifted ample material for remediation of its resources, among which chitosan is one of the most important and largely available biomaterial globally. Chitosan is a biopolymer obtained by deacetylation of chitin extracted from marine waste and its applications from drug delivery to food additives are broadly available. Chitosan exhibit several properties such as availability, low cost, high biocompatibility, and biodegradability. These properties make it biologically and chemically acceptable for use in various fields. Due to some limitations of pure chitosan, there has been a growing interest in modifying the chitosan in order to improve the original properties and widen the applications of pure phase chitosan. Various modified forms of chitosan and their associated applications are reviewed here with emphasis on their use in environmental remediation. The demand of chitosan in the global industrial market is growing which is briefly explained in this paper. Chitosan is used for water purification since a long time and still progress is going on for making it more efficient in the removal process. It can be used as a flocculent and coagulant, as an adsorbent for removing the contaminants like heavy metals, dyes, pesticides, antibiotics, biological contaminants from wastewater. Soil remediation using chitosan material is explained in this review. Various other applications such as drug delivery, food additives, tissue engineering are thoroughly reviewed.

Biosorption of Pb (II) and Zn (II) from aqueous solution by Oceanobacillus profundus isolated from an abandoned mine.

The present study investigated biosorption of Pb (II) and Zn (II) using a heavy metal tolerant bacterium Oceanobacillus profundus KBZ 3-2 isolated from a contaminated site. The effects of process parameters such as effect on bacterial growth, pH and initial lead ion concentration were studied. The results showed that the maximum removal percentage for Pb (II) was 97% at an initial concentration of 50 mg/L whereas maximum removal percentage for Zn (II) was at 54% at an initial concentration of 2 mg/L obtained at pH 6 and 30 °C. The isolated bacteria were found to sequester both Pb (II) and Zn (II) in the extracellular polymeric substance (EPS). The EPS facilitates ion exchange and metal chelation-complexation by virtue of the existence of ionizable functional groups such as carboxyl, sulfate, and phosphate present in the protein and polysaccharides. Therefore, the use of indigenous bacteria in the remediation of contaminated water is an eco-friendly way of solving anthropogenic contamination.

The Influence of the Addition of Plant-Based Natural Fibers (Jute) on Biocemented Sand Using MICP Method.

The microbial-induced carbonate precipitation (MICP) method has gained intense attention in recent years as a safe and sustainable alternative for soil improvement and for use in construction materials. In this study, the effects of the addition of plant-based natural jute fibers to MICP-treated sand and the corresponding microstructures were measured to investigate their subsequent impacts on the MICP-treated biocemented sand. The fibers used were at 0%, 0.5%, 1.5%, 3%, 5%, 10%, and 20% by weight of the sand, while the fiber lengths were 5, 15, and 25 mm. The microbial interactions with the fibers, the CaCO3 precipitation trend, and the biocemented specimen (microstructure) were also evaluated based on the unconfined compressive strength (UCS) values, scanning electron microscopy (SEM), and fluorescence microscopy. The results of this study showed that the added jute fibers improved the engineering properties (ductility, toughness, and brittleness behavior) of the biocemented sand using MICP method. Furthermore, the fiber content more significantly affected the engineering properties of the MICP-treated sand than the fiber length. In this study, the optimal fiber content was 3%, whereas the optimal fiber length was s 15 mm. The SEM results indicated that the fiber facilitated the MICP process by bridging the pores in the calcareous sand, reduced the brittleness of the treated samples, and increased the mechanical properties of the biocemented sand. The results of this study could significantly contribute to further improvement of fiber-reinforced biocemented sand in geotechnical engineering field applications.

Biological Route to Fabricate Silica on Cellulose Using Immobilized Silicatein Fused with a Carbohydrate-Binding Module.

Silicatein is an enzyme capable of catalyzing silica formation under mild conditions and is a promising catalyst for the fabrication of biohybrid materials. However, unfavorable aggregation of silicatein makes it unsuitable for use in material fabrication. In this study, a soluble protein tag (ProS2) and a carbohydrate-binding module (CBM) were used to develop a soluble and cellulose-binding fusion silicatein, ProS2-Sil-CBM, which can be efficiently immobilized on cellulose to form silica on it. ProS2-Sil-CBM was soluble in aqueous media and strongly bound to cellulose. ProS2-Sil-CBM bound on cellulose catalyzed the formation of a silica layer on the cellulose in the presence of tetraethyl orthosilicate as the substrate. Scanning electron microscopy (SEM) and surface elemental analysis confirmed the formation of silica on cellulose. This technique can be used to fabricate inorganic-organic hybrid materials to immobilize biomolecules and can be applied to develop novel biocatalytic systems, biosensors, and tissue culture scaffolds.

Cellulose-metallothionein biosorbent for removal of Pb(II) and Zn(II) from polluted water.

Intake of toxic trace elements in drinking water can lead to adverse health effects. To remove toxic trace elements from water, we developed a novel biosorbent composed of cellulose and a fusion protein. The fusion protein was constructed from metallothionein (MT) and a carbohydrate-binding module (CBM), where CBM can bind to cellulose while MT can capture heavy metal ions in solution. In a batch experiment, the biosorbent had maximum biosorption capacities for Pb(II) and Zn(II) ions of 39.02 mg/g and 29.28 mg/g, respectively. Furthermore, the biosorbent could be used in a semi-continuous system and showed good regeneration and recyclability. Both cellulose and the MT-CBM are environmentally friendly and renewable materials, and this biosorbent has great potential for efficient removal of toxic trace elements from polluted water.