Synthesis and Utilisation of Hybrid Metal-Carbonic Anhydrase Enzyme Carrier System for Soil Biocementation

Abstract

Biocementation is an emerging nature-inspired method of producing eco-friendly cement for soil stabilization. This paper used the bovine-derived carbonic anhydrase (CA) enzyme to catalyse the bioprecipitation of CaCO3 in a fine-grained soil and thus to biocement the soil. To increase the efficiency of the CA, an innovative copper–carbonic anhydrase (CA) hybrid was fabricated. This study is a proof-of-concept of the potential application of these enzyme carriers for soil biocementation. The hybrid carriers are aimed to enhance the stability, recovery and reusability of the enzyme used in the biocementation process. The results showed that the fabricated copper phosphate-based inorganic hybrid was stable throughout the duration of the tests (2 months) and under a wide range of pH and temperatures. Its enzymatic activity was enhanced compared to the free CA enzyme and it was proved suitable for soil biocementation. This was further confirmed by the SEM analysis. Additionally, the treated soil with the formulated hybrid carrier showed improved unconfined compressive strength, especially when the carriers were implemented into the soil by mixing. The material analysis by Raman spectroscopy confirmed calcium carbonate as the primary precipitate, consistent with soil biocementation. Overall, this innovative method of delivery of enzymes with enhanced stability and activity shows promise that, upon further development, it can be successfully used to increase the efficiency and sustainability of the biocementation process.