AMB Express最新文献

{"title":"Metabolic engineering of Parageobacillus thermoglucosidasius for thermophilic production of 1-butanol.","authors":"Pablo Doménech, Ivan Pogrebnyakov, Sheila Ingemann Jensen, Jasper L S P Driessen, Anders Riisager, Alex Toftgaard Nielsen","doi":"10.1186/s13568-025-01879-5","DOIUrl":"10.1186/s13568-025-01879-5","url":null,"abstract":"<p><p>1-Butanol is a promising compound for the ongoing green transition due to its potential both as a fuel and as a platform chemical, serving as a common intermediate for the bulk production of other valuable products. In this study, the thermophilic bacterium Parageobacillus thermoglucosidasius DSM 2542 was engineered to produce 1-butanol by introducing a butanol-producing pathway with thermostable enzyme variations derived from various thermophilic microorganisms. To achieve successful metabolic engineering, the relevant genes were inserted into two different chromosomal locations, employing both constitutive and inducible promoter systems. The resulting strains exhibited varying 1-butanol production depending on the promoter system used for the first half of the genes, with titres reaching up to 0.4 g/L when working under oxygen-limiting conditions. This serves as a foundation for further metabolic optimization to utilize the strain under industrial conditions.</p>","PeriodicalId":7537,"journal":{"name":"AMB Express","volume":"15 1","pages":"75"},"PeriodicalIF":3.5,"publicationDate":"2025-05-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12075064/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143956118","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Molecular identification, antibiotic susceptibility, and biofilm formation of airborne bacteria.","authors":"Malik Asif Hussain, Mubashir Zafar, Yusuf Saleem Khan, Kamaleldin B Said, Sadaf Anwar, Mohd Saeed, Mohammad A Abdulhakeem, Mejdi Snoussi, Mohd Adnan Kausar","doi":"10.1186/s13568-025-01861-1","DOIUrl":"10.1186/s13568-025-01861-1","url":null,"abstract":"<p><p>Pathogenic bacterial communities present in urban green spaces significantly affect human health, particularly for immunocompromised populations. The diverse range of pathogenic bacteria found in these areas poses substantial management challenges because of their high prevalence of antibiotic resistance, which can be life-threatening, particularly for immunocompromised individuals, including older adults and children. This study identified airborne bacterial species from 14 natural parks in the Hail region of the Kingdom of Saudi Arabia. Bacterial colonies isolated on blood agar plates were purified and characterised based on their morphological traits and their ability to secrete various virulence factors. A total of 28 distinct airborne bacterial species were isolated and purified. Antibiotic susceptibility tests revealed high resistance to fosfomycin (41.17%), ampicillin (17.64%), tetracycline (17.64%), and gentamicin (11.76%). Biofilm formation was evaluated qualitatively by slime production and quantitatively by crystal violet technique. The results revealed that 41.17% of the tested strains were non biofilm producers on polystyrene surfaces, 17.64% were weak biofilm formers, and 23.52% exhibited moderate biofilm formation. Notably, six strains exhibited strong biofilm-forming capabilities. Additionally, two bacteria from the Arthrobacter genus (A. crystallopoietes and A. saudimassiliensis) were identified. These findings provide valuable insights into the microbial composition of natural parks in the Hail region and highlight effective management strategies to mitigate health risks.</p>","PeriodicalId":7537,"journal":{"name":"AMB Express","volume":"15 1","pages":"74"},"PeriodicalIF":3.7,"publicationDate":"2025-05-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12064487/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143959727","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"In vitro investigation of Mangifera indica L. peel extracts: antibacterial, antioxidant, and docking studies.","authors":"Salwa M El-Sayed, Basma T Abd-Elhalim, Khalid A El-Dougdoug, Rawia F Gamal, Ghada G El-Bana, Nesma Nabil Ibrahim Mohamed","doi":"10.1186/s13568-025-01882-w","DOIUrl":"https://doi.org/10.1186/s13568-025-01882-w","url":null,"abstract":"<p><p>Marketers of antioxidants and antimicrobials view fruit peels as a special, readily available, reasonably priced, natural, eco-friendly, and lucrative source. Mangos (Mangifera indica L.) and their byproduct peels and kernels are nutrient-dense, distinctive, affordable, efficient, natural, and environmentally friendly sources of antibacterial agents, antioxidants, and other active chemicals. The current study aimed to prepare extracts of different degrees of polarity from mango peels, detect their active phytochemical compounds, and study their effects as antioxidants, antibacterials against food-borne pathogens, anti-biofilms, and anti-colon cancer in vitro. Phytochemical classes of compounds were screened using different standard methods. The most promising profile was for mango peel ethyl acetate extract (MPEE) due to the presence of a variety of phytochemicals including tannin, coumarin, alkaloids, flavonoids, phenols, steroids, and terpenoids at high concentrations compared to other mango peel extracts. Therefore, it was selected as the most valuable extract to examine its anti-colon cancer impact, anti-foodborne pathogenic bacteria, and antibiofilm. The anti-foodborne pathogenic activity of MPEE was evaluated against Enterococcus faecalis ATCC 7080, Staphylococcus aureus ATCC 5638, Salmonella typhi DSM17058, Bacillus cereus ATCC 11778, Shigella sonnei DSM 5570, and Escherichia coli ATCC 8739 that showed highly impact for all. At MIC and MBC values of 500 μg/ml, the MPEE had a 100% bactericidal spectrum; at lower concentrations of 125-250 µg/ml, no antibacterial action was seen. The MPEE had a biofilm inhibition percentage ranging between 98.75-53.33%; B. cereus had the highest percentage and S. sonnei had the lowest. Furthermore, The MPEE demonstrated an anticancer activity against human colon epithelium ATB-37 (Caco2) with an IC₅₀ of 430.36 µg/ml. Molecular docking modeling assessment illustrated top-ranked confirmations between major phytochemicals and target protein COX2: P00406 and NFKB: Q63369.</p>","PeriodicalId":7537,"journal":{"name":"AMB Express","volume":"15 1","pages":"73"},"PeriodicalIF":3.5,"publicationDate":"2025-05-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12061830/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143963834","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Engineering Pseudomonas aeruginosa for (R)-3-hydroxydecanoic acid production.","authors":"Shuai Wang, Haiying Yu, Kun Zhu","doi":"10.1186/s13568-025-01880-y","DOIUrl":"https://doi.org/10.1186/s13568-025-01880-y","url":null,"abstract":"<p><p>(R)-3-hydroxyalkanoic acids (R-3HAs) play a crucial role as essential chemicals serving as precursors or intermediates in the synthesis of a wide range of valuable compounds, such as pharmaceuticals, antibiotics, and food additives. Despite their significance, achieving industrial-scale production of R-3HAs, particularly medium-chain-length (mcl) R-3HAs, has been challenging due to the absence of suitable strains with efficient biosynthesis pathways. This study focuses on achieving the production of mcl R-3HA monomers by leveraging the \"substrate pool\" of R-3-(R-3-hydroxyalkanoyloxy) alkanoic acids (HAAs) which is synthesized by HAAs synthase RhlA. The process involved truncating the rhamnolipids synthesis pathway in Pseudomonas aeruginosa PAO1 by knocking out downstream genes rhlB and rhlC, leading to the accumulation and collection of intermediate HAAs from the culture supernatant. To enhance the production of HAAs further, a series of key genes in the β-oxidation pathway were knocked out, resulting in a titer of approximately 18 g/L. Subsequently, hydrolysis of HAAs was conducted under alkaline conditions, where the dimers could be rapidly and efficiently converted into monomers. The hydrolysis process was completed in 2.5 h at 80 °C using a 0.5 M NaOH solution. The primary hydrolysis product identified through GC-MS analysis was (R)-3-hydroxydecanoic acid (R-3HD) with a purity of 95%.</p>","PeriodicalId":7537,"journal":{"name":"AMB Express","volume":"15 1","pages":"72"},"PeriodicalIF":3.5,"publicationDate":"2025-05-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12055736/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143959955","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Surface energetics of antibiofilm property of dental material added with green synthesized copper nanoparticles.","authors":"Haris Saddique, Muhammad Aasim, Tariq Khan, Ajab Khan, Haroon Muhammad Ali, Umar Aziz","doi":"10.1186/s13568-024-01820-2","DOIUrl":"https://doi.org/10.1186/s13568-024-01820-2","url":null,"abstract":"<p><p>Dental caries and lesions are difficult to treat during cement repairs. A remarkable antimicrobial therapeutic biomaterial is needed to fight dental caries and recurrent necrotic lesions. This study used Mentha longifolia extract to synthesize Copper nanoparticles (CuNPs) with distinctive properties at room temperature (22-25 °C). These CuNPs were supplemented with cephalosporin antibiotics that act as a capping agent to explore their synergistic antibacterial potency. These nanoparticles were subjected to FTIR, XRD, UV-Vis spectrophotometry, and SEM for characterisation. These CuNPs capped with antibiotics were added to glass ionomer (GIC) cement. These GIC samples were divided into pure GIC and modified GIC samples. Antibiotic-supplemented CuNPs, conjugated with GIC, showed good effect against Methicillin-resistant Staphylococcus aureus, Enterococcus faecalis, Klebsiella pneumoniae and Pseudomonas aeruginosa as compared to conventional GIC, tested through a modified direct contact test. Among them, GIC enriched with cefotaxime-supplemented CuNPs exhibited excellent antibacterial effects, followed by Cefepime and Ceftriaxone-supplemented CuNPs, respectively. Pure GIC has the most negligible antibacterial effect. Further, the interaction of these modified GICs with the selected bacterial strains was studied using the extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) approach. The results show that the modified GIC effectively inhibited biofilm formation on dental implants.</p>","PeriodicalId":7537,"journal":{"name":"AMB Express","volume":"15 1","pages":"71"},"PeriodicalIF":3.5,"publicationDate":"2025-05-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12055682/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143963059","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Exploring the impact of comorbidities and drug resistance on mortality in ICU-acquired bloodstream infections.","authors":"Mahdieh Sharifzadeh Kermani, Shiva Pouradeli, Reihaneh Sadeghian, Zahra Momen Abadi","doi":"10.1186/s13568-025-01874-w","DOIUrl":"https://doi.org/10.1186/s13568-025-01874-w","url":null,"abstract":"<p><p>Hospital-acquired bloodstream infections (BSIs) seriously challenge critically ill patients. These infections in the ICU lead to significant morbidity, mortality, increased costs, and prolonged hospital stays. Therefore, the present study investigated this condition's prevalence and risk factors. This cross-sectional study was conducted on patients with neurological and nephrological issues admitted to general ICUs and trauma patients in two large hospitals in southeastern Iran. Bacteremia prevalence and mortality effects in ICU patients were analyzed from March 2020 to September 2022 during the COVID period. The results identified 127 patients with positive blood cultures, including 59 from the general ICU and 68 from the trauma ICU, yielding prevalences of 3.02% and 1.93%, respectively. The most common comorbidities included drug addiction (36.2%), chronic hypertension (35.4%), and type 2 diabetes (25.2%). Klebsiella pneumoniae was the most frequently isolated organism, followed by Staphylococcus epidermidis, Staphylococcus aureus, and Acinetobacter. The mortality rate was 93.2% in the general ICU and 60.3% in the trauma ICU. Risk factors associated with mortality included diabetes, hypertension, renal failure, drug addiction, a history of surgery in the last 30 days, ineffective experimental antibiotic treatment, and the administration of vasopressors. The prevalence of multiple drug resistance (MDR) was 33%, while Vancomycin-Resistant Enterococcus (VRE) was found in 9.4% of cases. These findings suggest that identifying and controlling risk factors associated with bacteremia in ICU patients is essential for reducing mortality.</p>","PeriodicalId":7537,"journal":{"name":"AMB Express","volume":"15 1","pages":"70"},"PeriodicalIF":3.5,"publicationDate":"2025-05-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12048367/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143952210","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Study of anti-Toxoplasma gondii effect of mPEG-PCL copolymeric loaded with pyrimethamine, in vitro.","authors":"Mobina Gholami, Hossein Danafer, Mitra Sadeghi, Ahmad Daryani, Seyed Abdollah Hosseini, Shirzad Gholami","doi":"10.1186/s13568-025-01876-8","DOIUrl":"https://doi.org/10.1186/s13568-025-01876-8","url":null,"abstract":"<p><p>The discovery of new drugs with minimal toxicity is crucially important in the search for effective treatments for toxoplasmosis. The study aimed to assess the effectiveness of pyrimethamine-loaded mPEG-PCL copolymeric nanoparticles (mPEG-PCL-Pyr) against Toxoplasma gondii (T. gondii) tachyzoites. The nanoparticles were fabricated using a nano-precipitation method and characterized using DLS and AFM. Through MTT assay, the anti-toxoplasmic activity was gauged. Healthy and infected cell viability, infection index, proliferation index, plaque count, and size were evaluated. Results indicated a maximum drug loading capacity of 11.23% in the nanoparticles. Toxicity testing on Vero cells infected with tachyzoites revealed notable cytotoxic effects at pyrimethamine-equivalent concentrations of 20 and 40 mg/mL in the mPEG-PCL copolymeric nanoparticle formulation. However, as the results indicated, the administration of mPEG-PCL-Pyr resulted in the reduction of intracellular proliferation, infection index, and the number and size of plaques in comparison to uninfected treated cells (P < 0.05). The synthesized Nano drug exhibited slightly better performance than pyrimethamine, despite the lack of statistical significance in the observed distinction (p > 0.05). The study demonstrated that mPEG-PCL copolymeric nanoparticles containing pyrimethamine effectively impede the in vitro replication of T. gondii. The study demonstrated that mPEG-PCL copolymeric nanoparticles containing pyrimethamine effectively impede the in vitro replication of T. gondii. The impact of pyrimethamine resembled that of the synthesized nano-drug on T. gondii tachyzoites, suggesting the potential of these nanoparticles as a promising avenue for toxoplasmosis treatment.</p>","PeriodicalId":7537,"journal":{"name":"AMB Express","volume":"15 1","pages":"69"},"PeriodicalIF":3.5,"publicationDate":"2025-05-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12048374/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143956434","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"In vitro and in vivo evaluation of the leishmanicidal and cytotoxic activities of chitosan and chitosan-amphotericin B.","authors":"Parisa Mousavi, Bahman Rahimi Esboei, Maryam Pourhajibagher, Azadeh Zolfaghari, Zabihollah Shahmoradi, Fatemeh Namdar, Somayyeh Ahmadi, Seyed Mahmood Mousavi, Fatemeh Parandin, Seyed Hossein Hejazi","doi":"10.1186/s13568-025-01877-7","DOIUrl":"https://doi.org/10.1186/s13568-025-01877-7","url":null,"abstract":"<p><p>Cutaneous leishmaniasis (CL), classified as a neglected tropical disease (NTD), is a significant public health concern caused by Leishmania protozoa. It is transmitted through the bites of infected female sandflies and manifests in various forms, ranging from localized skin ulcers to social stigma due to scarring. Numerous reports highlight the life-threatening side effects of glucantim, the first-line treatment for this disease, indicating a pressing need foralternative drugs. This experimental study aims to assess the anti-leishmanial effects of chitosan and chitosan- amphotericin B against Leishmania major (L. major) in vitro and in vivo. Chitosan and amphotricine B were purchased, and different concentrations were prepared. L. major promastigotes were cultured in RPMI-1640 medium. In vitro anti-leishmanial activity was assessed against the promastigotes of L. major using vital staining. For the in vivo assessment, lesion sizes were measured before and after ointment treatments in Bagg Albino mice (BALB/c). The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2 H-tetrazolium bromide (MTT) assay was utilized to evaluate the cytotoxic effects of chitosan and chitosan-amphotericin B at varying concentrations on the L929 cell line. Additionally, the in vitro hemolytic activity was measured using a spectrophotometric method. The in vitro and in vivo experiments demonstrated that chitosan-amphotericin B exhibited superior inhibitory effects against L. major compared to either chitosan or amphotericin B alone, and even against the positive control, particularly at higher concentrations (P < 0.05). Furthermore, cytotoxicity tests indicated that both chitosan and amphotericin, whether used separately or in combination, had no cytotoxic effects on the L929 cell line or human blood samples in vitro and did not impact liver enzymes in vivo (P < 0.05). The findings from this in vitro and in vivo study highlighted the impressive anti-leishmanial effects of chitosan, which were further enhanced with the addition of amphotericin B.</p>","PeriodicalId":7537,"journal":{"name":"AMB Express","volume":"15 1","pages":"68"},"PeriodicalIF":3.5,"publicationDate":"2025-04-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12040810/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143961056","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Method for automated high performance closed batch cultivation of gas-utilizing methanogens.","authors":"Walter Hofmann, Marco Orthofer, Nicolás Salas Wallach, Aquilla Ruddyard, Markus Ungerank, Christian Paulik, Simon K-M R Rittmann","doi":"10.1186/s13568-025-01872-y","DOIUrl":"10.1186/s13568-025-01872-y","url":null,"abstract":"<p><p>To advance the utilization of microbial cell factories in gas fermentation processes, their physiological and biotechnological characteristics must be understood. Here, we report on the construction and operation of a novel device, the Gas and Pressure Controller (GPC), which is specifically designed for the automated control of the headspace gas pressure of closed cultivation bottles and facilitates automated gassing, sparging, monitoring and regulation of the headspace volume operated in closed batch cultivation mode in real time.As proof of concept, the physiological and biotechnological characteristics of four autotrophic, hydrogenotrophic methanogenic archaea were examined to quantify novel physiological limits through the elimination of gas limitation during growth and methane formation. We determined unprecedented high maximum specific methane productivity (qCH₄) values for: Methanothermobacter marburgensis of 169.59 ± 12.52 mmol g^- 1 h^- 1, Methanotorris igneus of 420.21 ± 89.46 mmol g^- 1 h^- 1, Methanocaldococcus jannaschii of 364.52 ± 25.50 mmol g^- 1 h^- 1 and Methanocaldococcus villosus of 356.38 ± 20.79 mmol g^- 1 h^- 1. Obtained qCH₄ of M. marburgensis is more than 10-fold higher compared to conventional closed batch cultivation set-ups and as high as the highest reported qCH₄ value of M. marburgensis from fed-batch gas fermentation in stirred tank bioreactors. Furthermore, the GPC demonstrated reliable functionality with Methanococcus maripaludis, operating safely and autonomous during long term cultivation. This novel device enables optimal headspace pressure control, providing flexibility in application for various gas-fermenting biotechnological processes. It facilitates near optimal cultivation conditions in semi-continuous closed batch cultivation mode, the analysis of limiting factors in high-throughput experimental design and allows for automated biomass production of autotrophic, hydrogenotrophic methanogens.</p>","PeriodicalId":7537,"journal":{"name":"AMB Express","volume":"15 1","pages":"67"},"PeriodicalIF":3.5,"publicationDate":"2025-04-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12040808/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143961894","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Effect evaluation of repairing cement-mortar microbeams by microbial induced carbonate precipitation.","authors":"Peifeng Huang, Xinhua Yang, Yue Dai","doi":"10.1186/s13568-025-01881-x","DOIUrl":"https://doi.org/10.1186/s13568-025-01881-x","url":null,"abstract":"<p><p>The technique of microbially induced calcium carbonate precipitation (MICP) has a bright prospect in the repair of concrete structures with diseases, so the evaluation of the repair effect and its influencing factors are very important issues for civil engineers. In this paper, multi-phase mixed precipitate models are established by using the random particle generation and packing algorithm. Combined with the cohesive zone model, the deformation and failure behavior of notched cement-mortar microbeams before and after repair under three-point bending loading are numerically simulated. The recovery rate is proposed to characterize the repair effect of microbeam. The repair effect and the influences of the proportion of crystalline phases in the precipitate, particle size and notch location on it are evaluated. It is found that the recovery rate of peak load of microbeam decreases from 22.16 to 20.60% as the proportion of calcite increases from 0 to 1 for the combination case of calcite and vaterite in the particles of the precipitate. However, for the combination case of calcite and aragonite, as the proportion of calcite increases from 0 to 1, the recovery rate of peak load decreases from 35.01 to 20.77%. For only calcite grains as the particles of the precipitate, the recovery rate of peak load increases from 12.73 to 36.85% when the particle size increases from 2  to 3.4 μm. When the distance between the notch center and the microbeam midspan increases from 0 to 40 μm, the recovery rate of peak load increases from 20.44 to 77.26%. The effects of the proportion of crystalline phases, particle size and notch location on the repairing effect of microbeams can be explained from the population of matrix-particle interface and stress concentration degree in precipitate. Considering that the precipitate compositions can be regulated by the control of environmental and process parameters, the research in this paper is of great significance for the engineering application of MICP technique.</p>","PeriodicalId":7537,"journal":{"name":"AMB Express","volume":"15 1","pages":"66"},"PeriodicalIF":3.5,"publicationDate":"2025-04-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12037951/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144059102","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}