Enrichment, characterization, and sand consolidation application of urease active calcite-producing bacteria

Minerals such as calcium carbonate, which is prevalent in marble and limestone, are present naturally in rocks. Both physicochemical processes and microbial processes can result in the creation of calcium carbonate in nature, as is well documented. In this study, microbiologically induced calcite precipitation potential of three different Travertine-type water sources (Pamukkale Travertine Spring (PTS), Pamukkale Travertine Terraces (PTT), and Red Travertine of Karahayit (RTK)) using three different incubation media (NB, NB3, and ATCC1832) were investigated. After enrichment with ATCC1832 media, urease assays were positive for all of the microbial sources. The PTS and PTT were cultured with ATCC1832 medium for 48 h, which showed the best results for urease activity and microbial growth among other samples. Metagenome analyses indicated that PTT enriched with ATCC1832 media contains > 99% Firmicutes, while PTS enriched with ATCC1832 contains > 99% Proteobacteria at the Phylum level. Results from SEM-EDX and XRD analysis revealed that calcite and/or vaterite were the minerals that emerged from the mineralization of the PTS and PTT during incubation. The type of calcium carbonate crystals tended to change from one form to another when the incubation period extends from 72 to 120 h. Both the PTS and the PTT were able to precipitate calcite within the sand column. However, the bacteria from the PTT (26% CaCO₃) outperformed those from the PTS (18% CaCO₃) in terms of calcium carbonate deposition on the 21st day of incubation.