Background and objective: Algae-associated bacteria produce secondary metabolites that have a great biological impact. The aim of this study was isolation, identification and evaluation the antioxidant activities of the associated bacteria of seven algae, Padina pavonica, Dictyota dichotoma, Cystoseira myrica, Halimeda opuntia, Ulva lactuca, Digenea simplex and Jania sp. The bacteria were isolated, characterized and identified. Identification was carried out using 16S rRNA gene sequencing.
Materials and methods: The identified bacteria were belonging to 6 families, Alteromonadaceae, Bacillaceae, Lactobacillaceae, Pseudomonadaceae, Rhodobacteraceae and Vibrionaceae and 9 genera. The identified bacteria were belonging to genera, Alteromonas, Bacillus, Lysinibacillus Vibrio, Lactobacillus, Paracoccus, Leisingera, Pseudomonas and Pseudovibrio. The antioxidant activities of the bacterial ethyl acetate extracts was examined by scavenging DPPH (2,2-diphenyl-1-picrylhydrazyl) and FRAP (Ferric Reducing Antioxidant Power) methods.
Results: Out of the 17 isolated bacteria, Lactobacillus plantarum showed 95.7% free radical scavenging with EC50 = 17.7 μg mL-1, which is nearly similar to the positive control (Butylated Hydroxytoluene, BHT). The FRAP value of Lactobacillus extract was 2.00 mM ferric equivalent/mg of the extract. Phytochemical analysis of the bacterial extract revealed the presence of some secondary metabolites such as steroids, saponins, tannins, flavonoids, anthocyanin and betacyanin in all tested extracts.
Conclusion: The Red Sea algal associated bacteria have a great antioxidant potential that can be used in pharmaceutical industries.
Keywords: DPPH; FRAP; Lactobacillus plantarum; Marine bacteria; algae; antioxidant; ethyl acetate extract; phytochemicals; red sea.