ANTIMICROBIAL, ANTIOXIDANT, AND OPTIMAL CONDITION FOR EXOPOLYSACCHARIDES SECRATED FROM NEW LOCAL STRAIN-ISOLATE Bifidobacterium longum subsp. infantis strain Iraq-Basrah 3

Metabolic products of exopolysaccharide (EPS) generated by LAB strains have several biomedical effects. Our study focused on the isolation of a new strain of Bifidobacterium spp. From the sources of children's feces, examining them to choose the best EPS-producing strain, studying all the optimal conditions to increase the efficiency of producing more EPS, knowing the stage of their production, and finally introducing them into biomedical applications to test their antimicrobial and antioxidant activities. EPS is secreted by the most efficient new local strain Bifidobacterium longum subsp. infantis strain Iraq-Basrah 3 was extracted and purified, resulting in the highest production (2.08±0.41 g/L) in 1% (w/v) starch, which is the best carbon source with the best inoculum size of 1% (v/v) in 18 h at 37 °C and a pH value of 6.5. Coinciding with the best production phase, the generation time for the new strain was 32.2 min, and maximum production occurred after 16 h (2,45 g/L) to 20 h (2.14 g/L) between the end of the logarithmic phase and the early stationary phase. EPS exhibited antimicrobial activity, where S. aureus (17.24±1.2 mm) and E. coli (16.6±0.94 mm) were immediately resistant to EPS. In contrast, other pathogens were resistant to EPS, whereas strong antioxidant activity was observed at a concentration of 1500 µg/ml (84.43±0.95%). Through this study, we have proven that optimal conditions directly affect the quantity and production of EPS and that it has an inhibitory effect on some microbes in addition to being a natural antioxidant for DPPH free radicals.