Structural Characterization and Bioactivities of Two Exopolysaccharides from Bacillus sp. EM1-3. and Chelatococcus sp. EM3-1* Isolated from the Distinct Ain Ouarka Hot Spring: promising Biotechnological Applications

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Two exopolysaccharides (EPSs) of thermophilic Bacillus sp. EM1-3, and Chelatococcus sp. EM3-1* strains isolated from Ain Ouarka geothermal spring origin have been characterized and their biological potencies are reported which is the first investigation in Southwest Algerian geothermal spring. The Bacillus sp. EM1-3 and Chelatococcus sp. EM3-1* exhibited the highest yield (16.66 and 16.31 g/L, respectively), following an incubation at 50 °C for 48 h in minimal medium, each supplemented separately with glucose and sucrose as the sole carbon source, respectively. The obtained EPS were analyzed using FTIR, revealing multiple functional groups (C-O, C-O-C, and C-O-H) with peaks located within the “sugar region.” Furthermore, EPS from Bacillus sp. EM1-3 and Chelatococcus sp. EM3-1* demonstrate notable water solubility (70.32% and 87.96%), high water-holding capacities (826.8% and 709.1%), maximum DPPH free radical scavenging activities (87% and 83%), and remarkable ABTS scavenging activity reaching up to 99.56%. Also, these biopolymers exhibit antimicrobial effects against Staphylococcus aureus, Pseudomonas aeruginosa, and Candida albicans at concentrations of 1–3 mg/ml, with emulsifying indices of 40.73% and 42.36%, respectively. The EPS from Bacillus sp. EM1-3 shows non-hemolytic activity, whereas the EPS from Chelatococcus sp. EM3-1* displays hemolysis (31.5%). Overall, these findings highlight the diversity of the EPS and their functionality, providing evidence the first data on EPS provided from Ain Ouarka hot spring, especially from thermophilic Chelatococcus sp. EM3-1* strain. In addition, the eco-friendly, innovative, and sustainable EPS produced from Bacillus sp. might replace industrially additives in food and medical cosmetic industries.