## 5 Conclusions  
In this study, we investigated the delivery of immobilized carbonic anhydrase (CA) enzyme in hybrid carriers, as one possible way to overcome the challenges of enzyme instability in the EICP bioccentation process. A series of laboratory tests were conducted to fabricate a copper phosphate-based inorganic hybrid enzymatic delivery system that is stable and suitable for bioccentation with enhanced enzyme activity and efficiency. The key developments and findings from the study are as follows:  
1. The study achieved the synthesis and utilization of inorganic hybrid enzyme carriers with the morphological structure of flowers to bioccent soil.
2. The results showed that the bovine carbonic anhydrase enzyme enhanced the CO\({}_{2}\) hydration reaction, resulting in a bioprecipitation reaction and calcium carbonate production. This calcium carbonate was identified as calcite.
3. The immobilized CA enzyme effectively promoted the absorption of CO\({}_{2}\) into the calcium carbonate, which can be used for bioccentation with concurrent CO\({}_{2}\) sequestration.
4. It was demonstrated that the immobilised CA enzyme was very stable over long periods of time and within a wide range of pH and temperatures. This result has significant implications for bioccentation, as the improved enzyme stability would be helpful in various soil conditions, such as variable temperatures and pH, encountered during ground improvement. The fact that the stability was preserved over months also demonstrates that the hybrid carrier system can promote the reusability of the enzymes.
5. The carriers were successfully used in the soil to achieve bioccentation. Their capability as a practical enzyme delivery alternative was demonstrated.
6. Unconfined compressive strength values of fine-grained soil increased significantly upon implementation of the carriers, especially when mixing was used as a treatment implementation method.  
Figure 12: SEM image showing the length of CA-Cu hybrid carriers synthesized in this study.  
* The scanning electron microscope micrographs and Raman spectroscopy confirmed calcite as the primary precipitate formed, which can act as a bonding agent between soil particles to biocement soils.  
Thus, the carrier delivery system shows promise that upon further development, enzyme immobilisation can successfully be used for soil biocementation to increase the efficiency and overall sustainability of the EICP process.  
[PERSON], [PERSON], [PERSON] and [PERSON], carried out the experiment and analysed the results; [PERSON], [PERSON] and [PERSON] wrote the manuscript with support from [PERSON]; [PERSON], [PERSON] and [PERSON] supervised the project; [PERSON], [PERSON] and [PERSON] conceived the original idea. All authors have read and agreed to the published version of the manuscript.  
The European Commission funded this work under the Horizon 2020 Marie Sklodowska-Curie Individual Fellowships Grant Number 101025184 Project NOBILIS (Grant holder: London South Bank University).  
Not applicable.  
Data Availability StatementData sharing does not apply to this article.  
The authors thank Dr [PERSON] for conducting the SEM-EDS and Raman analyses, [PERSON] for conducting the XRD analyses and [PERSON] for the technical assistance.  
The authors declare no conflict of interest.