Said Dalia, Ibrahim Sahar M, Heikal Mohamed, Abdel-Monem Mohamed O, Dawwam Ghada E
Botany and Microbiology Department, Faculty of Science, Benha University, Benha, Egypt.
Chemistry Department, Faculty of Science, Benha University, Benha, Egypt.
Microb Cell Fact. 2025 Sep 16;24(1):203. doi: 10.1186/s12934-025-02837-3.
Microbial-induced calcium carbonate precipitation (MICP) has garnered significant attention for its construction and geotechnical engineering applications. In this study, 24 bacterial isolates were obtained from various edges of Wadi El-Natron Lake, Egypt, and subsequently assessed for their capacity for calcium carbonate (CaCO₃) precipitation. Among these isolates, strain D16 exhibited the highest CaCO₃ precipitation, yielding 0.404 g/100 mL, alongside robust bacterial growth and a final pH of 9.09. Morphological and biochemical characterization revealed that the isolate was rod-shaped, Gram-positive, Catalase-positive, Urease-positive, and Spore-forming. The optimal growth conditions for the isolate included a pH of 8, with ideal Ca²⁺ and urea concentrations of 25 mM and 20 g/L, respectively, at an incubation temperature of 30 °C over seven days. Molecular identification confirmed the isolate as Bacillus tropicus strain D16, which has been recorded in GenBank under the accession number PQ817131. The precipitated CaCO₃ was quantified and characterized using scanning electron microscopy (SEM) equipped with energy-dispersive X-ray (EDX) analysis, Fourier-transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), and the N₂ desorption/adsorption isotherm (BET) method. The effect of calcium carbonate nanoparticles (CaCO₃-NPs, denoted as NC) on the properties of cement paste was investigated. Four composite pastes were prepared with varying dosages of CaCO₃-NPs: NC0.0, NC0.5, NC1.0, and NC1.5. These pastes were subjected to a series of tests, including compressive strength, bulk density, total porosity, and chemically combined water content, over a hydration period of up to 90 days. The results demonstrated that the addition of NC enhanced the compressive strength of the cement paste up to an optimal dosage content of 0.5%, beyond which the strength decreased due to nanoparticle agglomeration. These findings were further corroborated by X-ray Diffraction (XRD), Differential Thermal Thermogravimetric Analysis (DTG/TGA), and Scanning Electron Microscopy (SEM), which provided microstructural and phase composition insights. Overall, the results indicate that the inclusion of an optimal dosage of CaCO₃-NPs can significantly improve the performance of cement composite pastes.
微生物诱导碳酸钙沉淀（MICP）因其在建筑和岩土工程中的应用而备受关注。在本研究中，从埃及纳特龙湖的各个边缘获得了24株细菌分离株，随后评估了它们沉淀碳酸钙（CaCO₃）的能力。在这些分离株中，菌株D16表现出最高的CaCO₃沉淀量，为0.404 g/100 mL，同时细菌生长旺盛，最终pH值为9.09。形态学和生化特征表明，该分离株为杆状、革兰氏阳性、过氧化氢酶阳性、脲酶阳性且产芽孢。该分离株的最佳生长条件包括pH值为8，在30°C的培养温度下培养7天，理想的Ca²⁺和尿素浓度分别为25 mM和20 g/L。分子鉴定证实该分离株为热带芽孢杆菌菌株D16，其在GenBank中的登录号为PQ817131。使用配备能量色散X射线（EDX）分析的扫描电子显微镜（SEM）、傅里叶变换红外（FT-IR）光谱、X射线衍射（XRD）和N₂脱附/吸附等温线（BET）方法对沉淀的CaCO₃进行了定量和表征。研究了碳酸钙纳米颗粒（CaCO₃-NPs，记为NC）对水泥浆体性能的影响。制备了四种不同剂量CaCO₃-NPs的复合浆体：NC0.0、NC0.5、NC1.0和NC1.5。在长达90天的水化期内，对这些浆体进行了一系列测试，包括抗压强度、堆积密度、总孔隙率和化学结合水含量。结果表明，添加NC可提高水泥浆体的抗压强度，直至最佳剂量含量为0.5%，超过该剂量后，由于纳米颗粒团聚，强度会降低。X射线衍射（XRD）、差示热重分析（DTG/TGA）和扫描电子显微镜（SEM）进一步证实了这些结果，这些分析提供了微观结构和相组成方面的见解。总体而言，结果表明，加入最佳剂量的CaCO₃-NPs可显著改善水泥复合浆体的性能。
