Biomineralization is a common phenomenon in nature, and the use of microbial-induced calcium carbonate precipitation (MICP) technology for engineering construction is a successful attempt to utilize natural biological phenomena, which has become a hot topic of current research. There are many factors affecting MICP, such as bacterial properties and external environmental factors. Many scholars have carried out a lot of research on these factors, but even under appropriate conditions, the MICP process still has the problem of low efficiency. According to different engineering, the tolerance and effect of bacteria in different environments are also different. At the same time, the cultivation and preservation of bacteria will also consume a large amount of raw materials, which is far more significant than the cost of engineering construction. The efficiency and cost limit the large-scale application of this technology in practical engineering. In response to these problems, researchers are exploring new ways to improve the efficiency of MICP technology. Based on the bacteria used in MICP, this paper explores the mechanism of bacteria in the process of MICP and reviews the improvement of bacteria from the perspective of efficiency improvement and economy.

Microbially induced carbonate precipitation (MICP) technology holds great potential in enhancing soil properties. MICP can be employed to enhance the stability and strength of diverse sandy soil, but it has the shortcoming of low curing efficiency. In response to the identified problem, this study aims to investigate an optimized treatment protocol that involves formulating a cementing solution in a hydrochloric acid (HCl) solution to enhance the solidification rate in the MICP reaction and evaluate its effectiveness. The results indicate that when preparing a 1 M cementing solution in a 0.2 M HCl solution, it promotes the rapid bonding of calcareous sand particles, resulting in an unconfined compressive strength (UCS) of 1312.6 kPa in the sand column after five treatments. Compared to the conventional test group, the experimental group containing HCl exhibited an approximately 1357% increase in UCS. The analysis unveiled the pivotal role of metal ions dissolved from calcareous sand by HCl in enhancing the UCS of MICP-treated calcareous sand. The proposed experimental methodology serves as a valuable tool for designing treatment strategies for MICP-cemented calcareous sand in practical engineering applications.

The Nanjing Circumvallation has been severely damaged due to natural factors, human interference, and urban expansion. Restoring this edifice serves not only as a preservation of historikcal and cultural values, but also as an advancement towards sustainable urban development. This research proposes an environmental ethical decision-making model (EEDM) grounded in sustainable urban development indicators. The model is then applied to the restoration of the Nanjing Circumvallation. Based on feedback from the research trial section, the renovation of the Circumvallation trial segment, guided by the EEDM, effectively embodies the core principles of sustainable urban development. By extending this model to the entire restoration project, it is feasible to achieve a harmonious balance between heritage preservation and urban sustainability. This methodology offers a novel framework for the restoration of similar heritage sites, ensuring the concurrent achievement of conservation and sustainable development goals. Furthermore, this approach holds considerable promise for fostering sustainable urban progression.

Microbially induced carbonate precipitation (MICP) is a promising biogeotechnical technology, but its large-scale application is constrained by the high cost and energy consumption of bacterial cultivation and harvesting. This paper presents a metal ion-induced flocculation strategy for the preparation and storage of high-density Sporosarcina pasteurii seed cultures. The flocculation performance and biological effects of Ca²⁺ and Fe³⁺ were systematically compared. Ca²⁺ achieved efficient flocculation through electrical double-layer compression while maintaining near-neutral pH, thereby preserving urease activity and bacterial viability. Even at an inoculation ratio of 1:10,000, the recovered bacteria exhibited rapid regrowth and high urease activity. In contrast, although Fe³⁺ induced rapid flocculation at low concentrations, the acidic conditions severely impaired bacterial viability and regrowth. Cryopreservation with glycerol at −20 °C maintained bacterial activity for at least 90 days and markedly outperformed storage at 4 °C. The recovered flocculated bacteria exhibited CaCO₃ precipitation performance comparable to that of freshly cultured suspensions. This study provides a simple, economical, and scalable strategy for the preparation and long-term storage of MICP seed cultures, facilitating the practical implementation of large-scale biogeotechnical applications.