## 4 Discussion
However, the cell wall of _Lactobacillus_ is primarily composed of peptidoglycan containing positively charged surface regions, particularly amino groups (-NH\({}_{3}\)+), which facilitate electrostatic attraction with the negatively charged biochar surface [26]. Despite the overall negative charge of both the biochar and _E. coli_ cells, significant adsorption of _E. coli_ was still observed. This suggests the involvement of additional mechanisms beyond electrostatic interactions. For instance, carboxylate groups on the biochar surface can act as hydrogen bond acceptors and interact with hydrogen bond-donating functional groups on bacterial surfaces, such as amines (-NH\({}_{2}\)) and hydroxyls (-OH) [27]. In addition, a biochar enriched in carboxylic groups tends to be hydrophilic, potentially leading to a higher affinity for hydrophilic bacteria such as _Escherichia coli_ compared to the generally more hydrophobic _Lactobacillus_ species [28]. The hydrophobicity of the _Lactobacillus_ species shows considerable variability, with notable differences not only between species but also among strains within the same species. For example, _Lactobacillus plantarum_, as previously demonstrated, is more hydrophobic than _Lactobacillus reuteri_[23]. This difference is significant because compared to _L. reuteri_, _L. plantarum_ is typically associated with a greater ability to adhere to hydrophobic surfaces, including mucosal tissues such as those found in the gastrointestinal tract [29; 30]. This difference in adhesion capacity may reflect their distinct abilities to colonize various environments. The greater hydrophobicity of _L. plantarum_ could contribute to its more efficient colonization of surfaces in the gastrointestinal tract, whereas _L. reuteri_ may exhibit lower colonization efficiency due to its lower hydrophobic properties. The membrane structure of _L. reuteri_ also generally contains fewer hydrophobic domains, which translates into a lower level of adhesion to surfaces such as VB biochar, which has hydrophobic characteristics [31]. These variations in membrane composition and surface interactions could help explain the different ecological niches occupied by these two species and their different functional roles in the microbiota. The results obtained could have important implications for nutritional applications. The high sorption capacity to bind pathogenic _E. coli_ suggests that orally administered biochar may be able to modulate the gut microbial population, thus minimizing the interference with normal and beneficial gut flora. In fact, [PERSON] et al. (2000) [18] demonstrated the ability of activated charcoal to adsorb the _E. coli_ O157:H7 strain in a dose-dependent manner and to absorb verotoxin 2 from the bacterial extract. Moreover, the activated charcoal did not demonstrate a strong affinity for _Enterococcus facecium_, _Bifidobacterium thermophilum_, and _Lactobacillus acidophilus_. The interaction between biochar and soil microorganisms has also been widely demonstrated since the addition of biochar promotes the growth of beneficial microorganisms [32]. Several studies have explored the use of biochar as a carrier for microorganisms due to its selective adsorption capacity and ability to create favorable environments for microbial growth. For instance, [PERSON] et al. (2022) [33] demonstrated that biochar combined with Herbaspirillum hutitiese increases the remediation of heavy metals in contaminated soils. Similarly, [PERSON] et al. (2015) [34] showed that maize straw biochar, when paired with Pseudomonas frederiksbergensis, improves plant growth and soil health in contaminatedenvironments. [PERSON] et al. (2023) [PERSON] et al. (2023) further supported this idea, highlighting the role of biochar in enhancing the activity of Aeromonas hydrophila for more efficient wastewater treatment. Biochar has also shown the potential to support various beneficial microbes, such as _Bacillus_ spp. and _Rhizobium_ spp., for bioremediation and plant growth promotion [36; 37; 38].