In vitro Assessment of Antioxidant and Antimicrobial Potential of Lactobacillus gasseri Strains Isolated from Human Milk and Infant Faeces

The present work demonstrates the antagonistic and antioxidant property of Lactobacillus gasseri lGs22 (MN258931), Lactobacillus gasseri MVS25(MN396621) isolated from human milk and Lactobacillus gasseri LBM220 (MN097539) isolated from exclusively breast-fed infant faeces.Antagonistic potential was assayed using agar well diffusion method against 17 food-borne and enteric pathogens.Further, in order to characterize the nature of inhibitory metabolites in culture supernatant, several preliminary experiments such as pH adjustment,treatment with protease, catalase and heat were performed.In addition, quantitative estimation of antimicrobial activity was performed using Time-kill assay against indicator pathogen Sh. flexneri type 2. Strains were further evaluated for antioxidant action such as scavenging of hydroxyl radical, DPPH radical and ABTS + radical.The capacity to resist 0.4 mM, 0.8mM and 1 mM hydrogen peroxide for 16 h was also studied.Results report the efficient inhibitory potential of Lact.gasseri strains with zone sizes ranging from moderate to very strong inhibition (10-22 mm) against most of the indicator pathogens employed in the current study.Also, inhibitory action of cell-free culture supernatant of isolates LBM220 and MVS25 when adjusted to pH 6.5 was significantly reduced, elucidating the production of organic acids, while isolate LGS22 produced hydrogen peroxide as inhibitory metabolite.Lact.gasseri isolates were found to significantly scavenge free radicals, with scavenging potential in range of (80.687-26.552%).It is concluded that these three Lact.gasseri isolates may be explored more for their bio-potential as food additive with antioxidant and antimicrobial activities.