Bacterial Carrier Research Articles

Forecasting Patient Early Readmission from Irish Hospital Discharge Records Using Conventional Machine Learning Models

Background/Objectives: Predicting patient readmission is an important task for healthcare risk management, as it can help prevent adverse events, reduce costs, and improve patient outcomes. In this paper, we compare various conventional machine learning models and deep learning models on a multimodal dataset of electronic discharge records from an Irish acute hospital. Methods: We evaluate the effectiveness of several widely used machine learning models that leverage patient demographics, historical hospitalization records, and clinical diagnosis codes to forecast future clinical risks. Our work focuses on addressing two key challenges in the medical fields, data imbalance and the variety of data types, in order to boost the performance of machine learning algorithms. Furthermore, we also employ SHapley Additive Explanations (SHAP) value visualization to interpret the model predictions and identify both the key data features and disease codes associated with readmission risks, identifying a specific set of diagnosis codes that are significant predictors of readmission within 30 days. Results: Through extensive benchmarking and the application of a variety of feature engineering techniques, we successfully improved the area under the curve (AUROC) score from 0.628 to 0.7 across our models on the test dataset. We also revealed that specific diagnoses, including cancer, COPD, and certain social factors, are significant predictors of 30-day readmission risk. Conversely, bacterial carrier status appeared to have minimal impact due to lower case frequencies. Conclusions: Our study demonstrates how we effectively utilize routinely collected hospital data to forecast patient readmission through the use of conventional machine learning while applying explainable AI techniques to explore the correlation between data features and patient readmission rate.

Exploring a cellulose-immobilized bacteria for self-healing concrete via microbe-induced calcium carbonate precipitation

Concrete is widely used in modern civil engineering due to its high compressive strength, abundance of raw materials, and simple production process. However, its brittleness makes it vulnerable to environmental factors, leading to cracks that impact its durability. Microbial-induced carbonate precipitation (MICP) technology has emerged as a promising solution, offering environmental benefits, real-time repair capabilities, and reduced manual intervention. This study focuses on enhancing the efficiency of calcium sources by identifying a strain with calcium ion adsorption abilities and pairing it with a mineralizing bacterium rich in urease production. Microorganisms were immobilized in a microcapsule using a cellulose-based material to explore the potential of cellulosic gel as a bacterial carrier. The gel was prepared through a sol-gel transformation process, incorporating a porogen to create a porous structure. Microcapsules with a particle size of 2.5–3.0 mm were successfully produced, enhancing their mechanical strength by 88.29 %. Examination of the microscopic structure of the cellulosic gel demonstrated its strong immobilization capacity for bacterial spores. The self-repairing effect of the gel on cracks was particularly effective under water curing conditions at 30–40 °C. After 28 days, cracks up to 0.3 mm wide were repaired, with a repair rate exceeding 90 % for cracks 0.1–0.2 mm wide.

Signal peptide replacement of Ag43 enables an efficient bacterial cell surface display of receptor-binding domain of coronavirus

To enable an efficient bacterial cell surface display with effective protein expression and cell surface loading ability via autotransporter for potential vaccine development applications, the inner membrane protein translocation efficiency was investigated via a trial-and-error strategy by replacing the original unusual long signal peptide of E. coli Ag43 with 11 different signal peptides. The receptor-binding domain (RBD) of coronavirus was used as a neutral display substrate to optimize the expression conditions, and the results showed that signal peptides from PelB, OmpC, OmpF, and PhoA protein enhance the bacterial cell surface display efficiency of RBD. In addition, the temperature has also a significant effect on the autodisplay efficiency of RBD. Our data provide further technical basis for the biotechnological application of Ag43 as a bacterial surface display carrier system and further potential application in vaccine development.

Microbial-inspired self-healing of concrete cracks by sodium silicate-coated recycled concrete aggregates served as bacterial carrier

Microbial-inspired self-healing of concrete cracks by sodium silicate-coated recycled concrete aggregates served as bacterial carrier

Optimization of nitrogen removal by immobilized heterotrophic nitrification aerobic denitrifying bacterium using response surface methodology

An innovative bacterial carrier complex embedded with polyvinyl alcohol and sodium alginate complex (P.S.) was developed, using the heterotrophic nitrification-aerobic denitrification (HN-AD) strain Paracoccus sp. QD-21, which was carefully selected from activated sludge. The performance of the immobilized bacterium on ammonia nitrogen, nitrate nitrogen, and nitrite nitrogen was thoroughly analyzed, aiming to investigate the synergistic effects of the P.S.-encapsulated bacterial carrier on the HN-AD strain QD-21. To assess the adaptability of the immobilized bacterium, various single-factor analysis experiments were conducted, including the assessment of carbon source, C/N, temperature, pH, rotational speed, and salinity. Subsequently, response surface methodology was employed to conduct further optimization, leading to the identification of optimum conditions (147.31 rpm, 36°C, C/N 8.72, pH 8). Under these conditions, an impressive ammonia nitrogen removal rate of 94.82 ± 0.82% was achieved. Furthermore, practical wastewater treatment experiments were carried out, demonstrating a remarkable 63.31% increase in ammonia nitrogen removal when the carrier with HN-AD bacterium attached was employed. Notably, the addition of a specific carbon source remarkably enhanced the treatment efficiency, resulting in a complete removal rate of 100%. These significant findings lay a solid foundation for the engineering application of the HN-AD bacterium and highlight the promising potential of the P.S.-encapsulated bacterial carrier complex in various applications.

Performance of self-healing mortar containing bacteria immobilized in alginate coated alkali activated lightweight aggregate

Among possible bacteria carriers available on the market, lightweight aggregate (LWA) shows great potential, as it is compatible with the mortar matrix and can retain high amounts of bacteria in the pores. However, the high energy needs to produce commercial LWA is a point of consideration in terms of producing sustainable mortar. Furthermore, the need of increasing the use of fly ash in countries, such as Indonesia, that rely for their electricity on coal power plants is still high. Therefore, LWA generated by cold bonding of fly ash was introduced here as an alternative bacteria carrier. Due to the high open porosity, a coating is needed to protect the bacteria and prevent leakage. Sodium alginate was applied as a coating on expanded clay and fly-ash based LWA containing cells or spores of Bacillus Sphaericus. The viability of spores and cells after encapsulation, and the compressive strength, the healing efficiency and the sealing efficiency of resulting mortar were investigated. The results show that the cells and spores of B. sphaericus are still viable and can actively decompose urea after encapsulation into both LWA types coated with sodium alginate. The strength decreased up to 11% in all mortar samples containing LWA coated with sodium alginate compared to mortar containing LWA without alginate coating. The sodium alginate coating improved the healing efficiency of mortar when cracks were created at 90 days. However high variability occurred for the sealing efficiency, due to the non-uniform crack geometry. In conclusion, fly ash based LWA as a bacterial carrier provides adequate healing performance, similar to commercial expanded clay, but slightly decreased the mechanical properties of resulting mortar.

Performance evaluation of self-healing recycled concrete using biomineralization modified recycled aggregate as bacterial carrier

The development of bacteria-based self-healing concrete relies on a carrier that is both compatible with the concrete matrix and capable of effectively protecting bacteria. This study utilized biomineralization modified recycled aggregate (RA) as a bacterial carrier to create bacteria-based recycled concrete with a strong self-healing capability. The workability, compressive strength, durability and self-healing performance of concrete were evaluated. The results showed that the quality of RA was significantly improved after biomineralization modification treatment due to the filling of bio-calcium carbonate in surface pores and microcracks, with an increase in apparent density of 1.9%, a decrease in water absorption and crushing index of 13.9% and 15.3%. The modified RA can provide better bacterial protection, thereby enhancing the crack self-healing efficiency of concrete by forming more bio-calcium carbonate healing product. For cracks with a width of about 0.4 mm, after healing of 56 days, the crack width repair ratio of bacteria-based recycled concrete was 94.5%, with an increase by 61.0% compared to that (only 58.7%) of ordinary recycled concrete. X-ray diffraction (XRD) results showed that the bio-calcium carbonate was calcite. The improvement of RA's quality will also benefit the performance enhancement of concrete. Compared to ordinary recycled concrete, the 28d compressive strength of bacteria-based recycled concrete was increased by 16.6%, the capillary water absorption coefficient was decreased by 37.5%, and the workability and resistance to chloride ion penetration was significantly improved.

Simultaneous detection of seven bacterial pathogens transmitted by flies using the reverse line blot hybridization assay

BackgroundTraditional methods for detecting insect-borne bacterial pathogens are time-consuming and require specialized laboratory facilities, limiting their applicability in areas without access to such resources. Consequently, rapid and efficient detection methods for insect-borne bacterial diseases have become a pressing need in disease prevention and control.MethodsWe aligned the ribosomal 16S rRNA sequences of seven bacterial species (Staphylococcus aureus, Shigella flexneri, Aeromonas caviae, Vibrio vulnificus, Salmonella enterica, Proteus vulgaris, and Yersinia enterocolitica) by DNASTAR Lasergene software. Using DNASTAR Lasergene and Primer Premier software, we designed universal primers RLB-F and RLB-R, two species-specific probes for each pathogen, and a universal probe (catch-all). The PCR products of seven standard strains were hybridized with specific oligonucleotide probes fixed on the membrane for specific experimental procedures. To evaluate the sensitivity of PCR-RLB, genomic DNA was serially diluted from an initial copy number of 1010 to 100 copies/μl in distilled water. These dilutions were utilized as templates for the PCR-RLB sensitivity analysis. Simultaneous detection of seven fly-borne bacterial pathogens from field samples by the established PCR-RLB method was conducted on a total of 1060 houseflies, collected from various environments in Lanzhou, China.ResultsThe established PCR-RLB assay is capable of detecting bacterial strains of about 103 copies/μl for S. aureus, 103 copies/μl for S. flexneri, 105 copies/μl for A. caviae, 105 copies/μl for V. vulnificus, 100 copies/μl for S. enterica, 105 copies/μl for P. vulgaris, and 100 copies/μl for Y. enterocolitica. The results demonstrate that the detection rate of the established PCR-RLB method is higher (approximately 100 times) compared to conventional PCR. This method was applied to assess the bacterial carrier status of flies in various environments in Lanzhou, China. Among the seven bacterial pathogens carried by flies, S. enterica (34.57%), S. flexneri (32.1%), and Y. enterocolitica (20.37%) were found to be the predominant species.ConclusionsOverall, this research shows that the rapid and efficient PCR-RLB detection technology could be a useful for surveillance and therefore effective prevention and control the spread of insect-borne diseases. Meanwhile, the experimental results indicate that urban sanitation and vector transmission sources are important influencing factors for pathogen transmission.Graphical

Development and assessment of an immobilized bacterial alliance that efficiently degrades tylosin in wastewater.

Microbial degradation of tylosin (TYL) is a safe and environmentally friendly technology for remediating environmental pollution. Kurthia gibsonii (TYL-A1) and Klebsiella pneumonia (TYL-B2) were isolated from wastewater; degradation efficiency of the two strains combined was significantly greater than either alone and resulted in degradation products that were less toxic than TYL. With Polyvinyl alcohol (PVA)-sodium alginate (SA)-activated carbon (AC) used to form a bacterial immobilization carrier, the immobilized bacterial alliance reached 95.9% degradation efficiency in 1 d and could be reused for four cycles, with > 93% degradation efficiency per cycle. In a wastewater application, the immobilized bacterial alliance degraded 67.0% TYL in 9 d. There were significant advantages for the immobilized bacterial alliance at pH 5 or 9, with 20 or 40 g/L NaCl, or with 10 or 50 mg/L doxycycline. In summary, in this study, a bacterial consortium with TYL degradation ability was constructed using PVA-SA-AC as an immobilized carrier, and the application effect was evaluated on farm wastewater with a view to providing application guidance in environmental remediation.

Application potentials of conch shell powder as a bacterial carrier for enhancing the Micro-Mechanical performance of biogenic gypsum plaster

Microbial-induced calcite precipitation (MICP) is a relatively novel technology that can improve the strength and durability of gypsum plasters. This present study seeks to explore the application potential of three different bacterial species (Bacillus subtilis, Bacillus sphaericus, and Sporosarcina pasteurii) on the mechanical strength, durability, and microstructure of the gypsum plaster. The use of porous conch shell powder (CSP) as a bacterial carrier through immobilization approach is also proposed in this work. The effect of vacuum impregnation of bacteria in the CSP with and without nutritional coating was attempted, and the results suggested the plaster mixes displayed higher performance with vacuum impregnation and the compressive strength was raised by around 7% over the ordinary plaster. The developed plaster indicated greater strength with fewer pores and improved durability by displaying increased water tightness, and the process of calcite production was evident for a period of up to 28 days through UPV monitoring. As SEM and XRD studies showed, microbial calcite precipitation plugged up the pores, making the microstructure dense and more durable.

Eco-friendly Biodegradation of Hydrocarbons Compounds from Crude Oily Wastewater Using PVA/Alginate/Clay Composite Hydrogels

Immobilized microorganisms especially bacteria are most used rather than free cells to be protected from the environmental conditions when being used for the bioremediation of environmental pollutants. Herein, two marine’s bacterial isolates were tested for their ability to decompose crude oil. The optimum conditions for effective bacterial degradation e.g., pH, temperature, and inoculum size were investigated. PVA-alginate-clay composite hydrogel beads with different types of incorporated mineral clays were prepared and tested as bacterial carrier for potential bioremediation. Synthesized composite hydrogels were physico-chemically characterized by FTIR, SEM, and thermal analyses. Results showed that, embedded degrading bacteria in PVA-alginate beads recorded degradation rates as 74 and 66.6% for both tested bacterial isolates (S and R) compared to 61.2 and 53% degradation rates by free cells, respectively. Where, attapulgite clay-containing beads recorded maximum degradation% as 78.8 and 75% for both bacterial isolates, when added to immobilization matrices and these percentages could be enhanced under optimal conditions. The 16S rRNA gene of the two marine oils degrading bacterial isolates were amplified and sequenced, where both isolates were identified as Pseudomonas stutzeri and Rhodococcus qingshengii with submitted accession numbers of ON908963 and ON908962, respectively. These results are referring to the ability of using both tested isolates for crude oil bioremediation process and embedded them into PVA-alginate-clay beads as hydrogel carrier under the optimum conditions.

Transfer of Enterococcus faecium and Salmonella enterica during simulated postharvest handling of yellow onions (Allium cepa)

Bacterial transfer during postharvest handling of fresh produce provides a mechanism for spreading pathogens, but risk factors in dry environments are poorly understood. The aim of the study was to investigate factors influencing bacterial transfer between yellow onions (Allium cepa) and polyurethane (PU) or stainless steel (SS) under dry conditions. Rifampin-resistant Enterococcus faecium NRRL B-2354 or a five-strain cocktail of Salmonella was inoculated onto onion skin or PU surfaces at high or moderate levels using peptone, onion extract, or soil water as inoculum carriers. Transfer from inoculated to uninoculated surfaces was conducted using a texture analyzer to control force, time, and number of contacts. Transfer rates (ratio of recipient surface to donor surface populations) of E. faecium (4–5%) were significantly higher than those of Salmonella (0.5–0.6%) at the high (7 log CFU/cm2) but not moderate (5 log CFU/cm2) inoculum levels. Significantly higher populations of E. faecium transferred from onion to PU than from PU to onion. The transfer rates of E. faecium were impacted by inoculum carrier (61% [onion extract], 1.6% [peptone], and 0.31% [soil]) but not by inoculation level or recipient surface (PU versus SS). Bacterial transfer during dry onion handling is significantly dependent on bacterial species, inoculation levels, inoculum carrier, and transfer direction.

Impacts of biomimetic self-healing of Lysinibacillus boronitolerans immobilized through recycled fine and coarse brick aggregates in concrete

Recycling waste bricks for concrete is cost-effective and eco-friendly but may impact strength and durability. A promising solution is biomimetic self-healing concrete that uses bacteria to repair cracks. The efficacy of this approach is contingent upon the bacterial strain, carrier medium, medium size, and immobilization utilized. Nevertheless, it remains uncertain how carrier size affects biomimetic self-healing concrete when the same carrier substance and immobilization technique are used. This study explored using Lysinibacillus boronitolerans (LBBT) to develop biomimetic self-healing concrete using recycled fine brick aggregate (RFBA) as a carrier medium. Recycled coarse brick aggregate (RCBA) was also employed for the relative evaluation of the impact of carrier size in biocrete. Results revealed that adding LBBT to concrete through RFBA resulted in significant improvements in strength and toughness. Compressive, split tensile, and flexural strength increased by 16.2%, 17.6%, and 22.0% respectively, while compressive and flexural toughness improved by 51.0% and 27.6%. The abundant RFBA particles ensured the even distribution of LBBT throughout the mixture. RCBA immobilization facilitated self-healing, achieving 0.6 mm of crack healing with 89.7% compression strength recovery and a 26.0% healing potential. The achievement can be attributed to the macro-voids and the stiffened structure of RCBA. Additionally, forensic investigations confirm the presence of microbial induced carbonate precipitation. Thus, RFBA is a promising immobilizer for LLBT, exhibiting a greater impact on mechanical performance due to its smaller particle size. In contrast, RCBA facilitates self-healing by entrapping the biomimetic agent, despite its lower abundance.

Degradation of aniline: sodium alginate/modified pomelo cellulose double cross-linking system as a bacterial immobilization carrier.

Pectin cellulose grafted with glycidyltrimethylammoniochloride (GTMAC) was successfully obtained following the processes of depectinfibrillation and cellulose cationization using ordinary Shatian pomelo peel produced in Yongzhou, Hunan, as the raw material. This is the first report on a new type of functionalized sodium alginate-immobilized material prepared from the fibers of pomelo peel. The material was prepared by combining modified pomelo peel cellulose and sodium alginate following the processes of physical and chemical double cross-linking. The prepared material was used to embed the target bacteria to achieve the biodegradation of p-aniline. The concentration of CaCl2 was adjusted when the alginate gelled, and the alginate to yuzu peel cellulose ratio was tuned. The immobilized material-embedded bacteria help achieve the best degradation effect. Bacteria are embedded during the process of the degradation of aniline wastewater, and the functionalization of the cellulose/sodium alginate-immobilized material results in unique surface structure performance. The performance of the prepared system is better than that of the single sodium alginate-based material characterized by a large surface area and good mechanical properties. The degradation efficiency of the system is improved significantly for the cellulose materials, and the prepared materials can potentially find applications in the field of bacteria-fixed technology.

The DedA superfamily member PetA is required for the transbilayer distribution of phosphatidylethanolamine in bacterial membranes

The sorting of phospholipids between the inner and outer leaflets of the membrane bilayer is a fundamental problem in all organisms. Despite years of investigation, most of the enzymes that catalyze phospholipid reorientation in bacteria remain unknown. Studies from almost half a century ago in Bacillus subtilis and Bacillus megaterium revealed that newly synthesized phosphatidylethanolamine (PE) is rapidly translocated to the outer leaflet of the bilayer [Rothman & Kennedy, Proc. Natl. Acad. Sci. U.S.A. 74, 1821-1825 (1977)]but the identity of the putative PE flippase has eluded discovery. Recently, members of the DedA superfamily have been implicated in flipping the bacterial lipid carrier undecaprenyl phosphate and in scrambling eukaryotic phospholipids invitro. Here, using the antimicrobial peptide duramycin that targets outward-facing PE, we show that Bacillus subtilis cells lacking the DedA paralog PetA (formerly YbfM) have increased resistance to duramycin. Sensitivity to duramycin is restored by expression of B. subtilis PetA or homologs from other bacteria. Analysis of duramycin-mediated killing upon induction of PE synthesis indicates that PetA is required for efficient PE transport. Finally, using fluorescently labeled duramycin we demonstrate that cells lacking PetA have reduced PE in their outer leaflet compared to wildtype. We conclude that PetA is the long-sought PE transporter. These data combined with bioinformatic analysis of other DedA paralogs argue that the primary role of DedA superfamily members is transporting distinct lipids across the membrane bilayer.

Investigating the potential for porous ceramics as bacterial carrier in self-healing cemented paste backfill

Waste porous ceramic (WPC), which remains in the industrial manufacturing process, is difficult to be disposed of. This study proposes a new idea for resource utilization of WPC, which means that WPC as a bacterial carrier applies in self-healing cemented paste backfill. The authors investigated the effects of WPC pore size, initial crack size, and bacterial concentration on the crack self-healing ratio of the backfill, analyzed the crack self-healing evolution process by photographing, and finally used a series of instruments to characterize the physical phase at the sample fracture and explain the mechanism. The results showed that the crack self-healing ratio of WPC with small pore size (pore size distribution of 1–2 mm) as the bacterial carrier was 13–22% higher than that of WPC with large pore size (pore size distribution of 3–4 mm) at 3–7 days. Also, the strength recovery ratio of the cemented paste backfill can be improved to 10–23% when adding bacteria-WPC. The self-healing ratio can reach 100% in 28 days for initial crack widths less than 1 mm, while the self-healing ratio decreases to 98% for widths near 2 mm. Additionally, the biomineralization ratio of the 1.5 mol/L embedded bacterial solution was 2.77–4.68% higher than that of 1.0 mol/L. WPC can effectively release the embedded bacterial solution once the backfill cracks appear, which proves the feasibility of WPC as a bacterial carrier. This study also lays the experimental and theoretical foundation for porous ceramic management.

Advances in Escherichia coli Nissle 1917 as a customizable drug delivery system for disease treatment and diagnosis strategies.

With the in-depth and comprehensive study of bacteria and their related ecosystems in the human body, bacterial-based drug delivery system has become an emerging biomimetic platform that can retain the innate biological functions. Benefiting from its good biocompatibility and ideal targeting ability as a biological carrier, Escherichia coli Nissle 1917 (ECN) has been focused on the treatment strategies of inflammatory bowel disease and tumor. The advantage of a bacterial carrier is that it can express exogenous protein while also acting as a natural capsule by releasing drug slowly as a result of its own colonization impact. In order to survive in harsh environments such as the digestive tract and tumor microenvironment, ECN can be modified or genetically engineered to enhance its function and host adaptability. The adoption of ECN carries or expresses drugs which are essential for accurate diagnosis and treatment. This review briefly describes the properties of ECN, the relationship between ECN and inflammation and tumor, and the strategy of using surface modification and genetic engineering to modify ECN as a delivery carrier for disease treatment.

Alkali activated lightweight aggregate as bacterial carrier in manufacturing self-healing mortar

A bacteria-based self-healing concrete has been proposed for the autonomous repair of micro-cracks. However, the bacteria need protection to survive in concrete until cracks would appear. Here, vegetative cells of Bacillus sphaericus have been encapsulated into novel alkali activated lightweight aggregate (LWA) generated from fly ash and Sidoarjo volcanic Mud (Lusi). For the production of self-healing mortar, 30% by volume of the fine aggregates were replaced by bacteria impregnated LWA. The mechanical properties of the resulting mortar, the healing performance, sealing efficiency and healing product morphology were investigated. The results show that with vegetative cells as healing agent, a significant decrease in healing performance was observed when cracks were fabricated at later age. Furthermore, fly ash based LWA provided comparable healing and sealing performance as a commercial expanded clay carrier used for comparison. In addition, the fly ash-based LWA carrier provided excellent autogenous healing in young mortar.

Gut dysbiosis and bacterial translocation in the aneurysmal wall and blood in patients with abdominal aortic aneurysm.

Inflammation plays a part in the development of abdominal aortic aneurysm (AAA), and the gut microbiota affects host inflammation by bacterial translocation. The relationship between abdominal aortic aneurysm and the gut microbiota remains unknown. This study aimed to detect bacterial translocation in the aneurysmal wall and blood of patients with abdominal aortic aneurysm, and to investigate the effect of the gut microbiota on abdominal aortic aneurysm. We investigated 30 patients with abdominal aortic aneurysm from 2017 to 2019. We analysed the aneurysmal wall and blood using highly sensitive reverse transcription-quantitative polymerase chain reaction, and the gut microbiota was investigated using next-generation sequencing. In the 30 patients, bacteria were detected by reverse transcription- quantitative polymerase chain reaction in 19 blood samples (detection rate, 63%) and in 11 aneurysmal wall samples (detection rate, 37%). In the gut microbiota analysis, the Firmicutes/Bacteroidetes ratio was increased. The neutrophil-lymphocyte ratio was higher (2.94 ± 1.77 vs 1.96 ± 0.61, P < 0.05) and the lymphocyte-monocyte ratio was lower (4.02 ± 1.25 vs 5.86 ± 1.38, P < 0.01) in the bacterial carrier group than in the bacterial non-carrier group in blood samples. The volume of intraluminal thrombus was significantly higher in the bacterial carrier group than in the bacterial non-carrier group in aneurysmal wall samples (64.0% vs 34.7%, P < 0.05). We confirmed gut dysbiosis and bacterial translocation to the blood and aneurysmal wall in patients with abdominal aortic aneurysm. There appears to be a relationship between the gut microbiota and abdominal aortic aneurysm.

Experimental and statistical investigation on strength and microcracks remediation in cement mortar using expanded vermiculite as a bacterial carrier

Cement based building materials have been used in the field of construction for decades. Among the various applications, lightweight aggregates are very common for thermal insulation, improved acoustic performance, and lightweight construction. This study reported the healing of micro-cracks using expanded vermiculite as a bacterial carrier for crack healing. The expanded vermiculite was adsorbed with bacterial cells and subsequently coated using sodium silicate as the first layer and cement slurry as the second layer. The cement mortar was prepared using dual-coated expanded vermiculite as a bacterial carrier. The expanded vermiculite's water holding capacity and bacterial immobilization capacity were 180% and 1.62×109 cells/gram, respectively. The fine aggregate was replaced in the cement mortar using expanded vermiculite in 0%, 10%, 15%, 20%, and 25% to find the optimum replacement percentage for crack remediation without compromising strength and durability. The performance of this cement mortar in terms of strength, durability, and crack remediation capacity was assessed. The test results showed that 20% replacement with a 5% silica fume combination was effective. The crack area and width were determined by using ImageJ analysis. The bacteria remediated a crack width of 0.92 mm by precipitating calcite crystals was observed under FESEM and confirmed using EDS. For each test process, regression equations were formed by taking into account the variables that influence the compressive strength and healing efficacy. The variables' significance and the optimum vermiculite proportion were determined using ANOVA analysis. The factors were significant with a p-value less than 0.05, and the experimental and ANOVA general linear model predicted that 20% replacement is optimum.