# Enhancing the Strength of Mine Residue Soil by Bioremediation Combined with Biopolymers
## 4 Conclusions  
Based on the UCS tests performed on previously disturbed samples (two cycles of percolation, extraction and homogenization) of mine residue soil stabilized with Portland cement, or with the biopolymers XG and CMC, applied individually or combined with the biostimulation and bioaugmentation techniques, allowed for the following conclusions:  
* Both biopolymers (XG and CMC), when applied individually, are effective stabilizers of the mine residue soil, showing better CMC results in terms of unconfined compressive strength than Portland cement when applied with the same content (1% of the dry unit weight of the soil);
* The biostimulation of the autochthonous community of the mine residue soil was revealed to be a non-effective technique, even when combined with the biopolymers or with the Portland cement;
* The bioaugmentation of the mine residue soil with the bacterial strain _Diaphorobacter polyhydroxybutyratorans_ B2A2W2, when combined with the biopolymer xanthan gum (XG), exhibited a good performance in terms of stress-strain compressive behavior, even after the samples were disturbed. Improvements in the unconfined compressive strength of up to 27% were observed compared to the respective control test. Through further research and application, these bio-techniques have the potential to revolutionize soil engineering practices, offering environmentally friendly alternatives for sustainable soil stabilization, and contributing to a greener and more sustainable future. Conceptualization, A.A.S.C. and P.V.M. ; methodology, A.A.S.C. and P.V.M. ; validation, A.A.S.C., J.B.C. and P.V.M. ; formal analysis, A.A.S.C., J.B.C., R.B. and P.V.M. investigation, J.B.C. ; resources, A.A.S.C. and P.V.M. ; data curation, A.A.S.C. and J.B.C. ; writing--original draft preparation, A.A.S.C. ; writing--review and editing, J.B.C., R.B. and P.V.M. ; supervision, A.A.S.C. and P.V.M. ; project administration, A.A.S.C. and P.V.M. ; funding acquisition, P.V.M. All authors have read and agreed to the published version of the manuscript. This research was funded by FEDER funds through the program COMPETE--Programa Operacional Factores de Competitividade and by national funds through FCT--Fundacao para a Ciencia e Tecnologia, under the projects UID/EMS/00285/2020, UIDB/00102/2020, and LA/P/0112/2020, by the Project ERA-MIN-2019_67-Reviving and by BIORECOVER Horizon2020 under grant agreement No 821096, supported under Horizon 2020 the European Union's Framework for Research and Innovation. [PERSON] was supported by a PhD research grant (2022.13542.BD) from FCT/MCTES through national funds. Not applicable. +++ ==WARNING: Truncated because of repetitions==
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