Biocementation mediated by native Carbonic Anhydrase-producing microbes.

This study investigated the feasibility of biocementing a fine-grained foundation soil from the East Anglia railway network via the carbonic anhydrase (CA) pathway. This pathway is a promising way of improving the mechanical properties of soils by biocementation while sequestering CO2 during the process. To achieve the aim of this research, forty CA-producing bacterial isolates from soil layers below a railway embankment in East Anglia, UK, were screened and selected using a qualitative CA activity assay. Three of these bacteria expressed high and stable CA enzyme activity and were further characterised by their morphological, molecular, and enzyme profile characteristics. Bioaugmentation was then employed to biocement the soil from the site using the native CA-producing bacteria isolated from the soil. The unconfined compressive strength and calcite content of the treated soil were determined. Preliminary results showed a substantial increase in soil unconfined compressive strength upon biocementation treatment. Although further geotechnical testing is the subject of future work, the unconfined compressive strength and calcite content results obtained so far proved biocementation of the fine-grained soil and showed promise that the CA biocementation route can be further developed as a successful and environmentally friendly soil stabilization technique, with the added advantage of sequestering CO2 from the atmosphere or using captured waste CO2, during the biocementation process.