School of Chemical and Biotechnology, SASTRA Deemed to Be University, Thirumalasamudram, Thanjavur, Tamil Nadu, 613 401, India.
Curr Microbiol. 2024 Oct 4;81(11):387. doi: 10.1007/s00284-024-03899-z.
Microbially induced calcium carbonate precipitation (MICP) is a soil remediation method that has emerged as a viable and long-term solution for enhancing soil mechanical qualities. The technique of MICP that has been extensively researched is urea hydrolysis, which occurs naturally in the environment by urease-producing bacteria as part of their fundamental metabolic processes. The objectives of the current study include screening and identifying native ureolytic bacteria from soil in Uttarakhand, optimizing growth factors for increased urease activity, and calcite precipitation by the bacteria using response surface methodology. Additionally, it was assessed how well the isolated bacteria in the medium biomineralized when using synthetic media and cheaper alternatives such as cow urine and eggshell as sources of urea and Ca, respectively. The isolated strain identified as Lysinibacillus sp. was found to be the very active strain after soil samples were screened for ureolytic bacteria. It was discovered that optimization studies with values of pH 8, urea concentration (0.8 M), inoculum concentration (3%), and incubation time (48 h) yielded a higher activity of 33.7 U/mL (threefold increase), and a higher calcium carbonate precipitation (enzyme activity: 10.96 U/mL, pH: 8.92, soluble Ca⁺: 25.53 mM and insoluble Ca⁺: 0.856 g). The calcite precipitation in broth media supplemented with ready-made substrates and alternative sources demonstrated a similar result of increased pH and ammonia release. Thus, the current study successfully paves the way for several possibilities to stabilize the slopy soils prone to landslides and erosion in Uttarakhand and pinpoint an economic approach through biomineralization.
微生物诱导碳酸钙沉淀（MICP）是一种土壤修复方法，已成为增强土壤机械性能的可行和长期解决方案。经过广泛研究的 MICP 技术是尿素水解，它是由产脲酶的细菌在环境中自然发生的，作为其基本代谢过程的一部分。本研究的目的包括从北阿坎德邦的土壤中筛选和鉴定本土产脲细菌，优化提高脲酶活性的生长因素，并通过响应面法使细菌沉淀碳酸钙。此外，还评估了分离的细菌在使用合成培养基和更便宜的替代物（如牛尿和蛋壳）作为尿素和 Ca 源时在培养基中的生物矿化效果。在对产脲细菌的土壤样本进行筛选后，发现分离出的菌株被鉴定为Lysinibacillus sp.，是一种非常活跃的菌株。研究发现，在优化研究中，pH 值为 8、尿素浓度（0.8 M）、接种物浓度（3%）和孵育时间（48 h）的值可使酶活提高 33.7 U/mL（提高三倍），碳酸钙沉淀量更高（酶活：10.96 U/mL，pH 值：8.92，可溶 Ca⁺：25.53 mM，不溶 Ca⁺：0.856 g）。在添加现成底物和替代物的培养基中进行碳酸钙沉淀实验，也得到了类似的结果，即 pH 值和氨释放增加。因此，本研究成功地为北阿坎德邦易发生滑坡和侵蚀的坡地土壤稳定提供了多种可能性，并通过生物矿化找到了一种经济的方法。
