[2S03a] 07. Biocatalysis Engineering for Sustainable Bioprocessing - Part 2

3:45 PM - 4:00 PM JST(6:45 AM - 7:00 AM UTC)

[2Biocat-10-KL] Biocementation based on microbially induced carbonate precipitation for environmentally friendly solidification technique

○Kazunori Nakashima¹, Thiloththama Hiranya Kumari Nawarathna^1,2, Wilson Mwandira¹, Chikara Takano¹, Satoru Kawasaki¹ (1. Hokkaido University (Japan), 2. University of Jaffna (Sri Lanka))

Keywords:

biomineralization,biocementation,calcium carbonate precipitation,urease

Cement and concrete are essential materials for modern infrastructure; however, their production is associated with significant CO₂ emissions. To address this issue, environmentally friendly and low-energy alternatives are required. Urease is an enzyme that hydrolyzes urea to produce carbonate ions and ammonia. In the presence of Ca²⁺ ions in the reaction system, calcium carbonate (CaCO₃) precipitates, which acts as a cementing material to solidify target materials (such as sand, soil, and slug) under ambient conditions. The process utilizing urease-producing microorganisms to induce CaCO₃ formation is called microbially induced carbonate precipitation (MICP).We isolated a high-urease-activity bacterium, Pararhodobacter sp. SO1, from beachrock environments and investigated its applicability to bio-cementation. This strain maintains high urease activity for more than 15 days, which is advantageous for improving the efficiency of CaCO₃ precipitation and soil solidification. In addition, its carbonic anhydrase activity and microbial metabolites are suggested to contribute to enhanced mineralization.To further improve the mechanical properties of bio-cement, we examined the incorporation of biopolymers. The addition of cationic polypeptides and polysaccharides altered CaCO₃ crystal morphology and increased solidification strength. Furthermore, we designed artificial proteins combining chitin-binding and calcium-binding domains inspired by crustacean exoskeleton structures. The resulting organic–inorganic hybrid system significantly enhanced both stiffness and toughness of the consolidated materials.We also investigated the application of bio-cementation for heavy metal remediation. The MICP process effectively immobilized Pb²⁺ ions by incorporating them into CaCO₃ precipitates, achieving complete removal from aqueous solutions. Field studies in mine tailings in Zambia demonstrated successful solidification and the potential for in situ bioremediation of heavy metal contamination. Additionally, urease-producing and heavy metal-tolerant bacteria capable of extracellular polymeric substance (EPS) production were identified, indicating multiple mechanisms for heavy metal immobilization.These results demonstrate that bio-cementation is a promising green technology for both sustainable construction and environmental remediation.