This study investigates the potential of bio-inspired solutions to enhance the geomechanical properties of sandy soil through the biocementation process, using two bacterial strains: Sporosarcina pasteurii and Pseudomonas M47T1. Laboratory experiments were conducted to evaluate the ability of these bacteria to induce calcium carbonate precipitation, a key process for improving soil stability. The research design included assessment of ureolytic activity, unconfined compressive strength, and the effects of factors such as curing time on biostabilised soil. Results demonstrated that both bacterial strains were highly effective in promoting calcium carbonate precipitation, leading to significant improvements in the soil's geomechanical properties. Despite challenges posed by environmental conditions for bacterial growth, the findings showed that Sporosarcina pasteurii and Pseudomonas M47T1 performed satisfactorily, yielding stable soil structures. Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS) confirmed the presence of calcium carbonate (CaCO₃). The study underscores the potential of these bacterial strains as effective agents for sustainable and bio-inspired approaches to soil stabilization, introducing practical solutions for improving the mecha- nical performance of natural sandy soils.

Chemical stabilization of soils is one of the most used techniques to improve the properties of weak soils in order to allow their use in geotechnical works. Although several binders can be used for this purpose, Portland cement is still the most used binder (alone or combined with others) to stabilize soils. However, the use of Portland cement is associated with many environmental problems, so microbiological-based approaches have been explored to replace conventional methods of soil stabilization as sustainable alternatives. Thus, the use of biopolymers, produced by microorganisms, has emerged as a technical alternative for soil improvement, mainly due to soil pore-filling, which is called the bioclogging method. Many studies have been carried out in the last few years to investigate the suitability and efficiency of the soil–biopolymer interaction and consequent properties relevant to geotechnical engineering. This paper reviews some of the recent applications of the xanthan gum biopolymer to evaluate its viability and potential to improve soil properties. In fact, recent results have shown that the use of xanthan gum in soil treatment induces the partial filling of the soil voids and the generation of additional links between the soil particles, which decreases the permeability coefficient and increases the mechanical properties of the soil. Moreover, the biopolymer’s economic viability was also analyzed in comparison to cement, and studies have demonstrated that xanthan gum has a strong potential, both from a technical and economical point of view, to be applied as a soil treatment.

The building of civil engineering structures on some soils requires their stabilisation. Although Portland cement is the most used substance to stabilise soils, it is associated with a lot of environmental concerns. Therefore, it is very pertinent to study more sustainable alternative methodologies to replace the use of cement. Thus, this work analyses the ability of the more sustainable xanthan-like biopolymer, produced by Stenotrophomonas maltophilia Faro439 strain (LabXLG), to reduce the permeability of a sandy soil. Additionally, the effectiveness of this LabXLG is compared with the use of a commercial xanthan gum (XG) and cement for various hydraulic gradients and curing times. The results show that a treatment with either type of XG can be used to replace the cement over the short term (curing time less than 14 days), although a greater level of effectiveness is obtained with the use of the commercial XG, due to its higher level of purity. The soil treatment with LabXLG creates a network of fibres that link the soil particles, while the commercial XG fills the voids with a homogeneous paste.