Investigation on characterization, antifouling and cytotoxic properties of zinc oxide nanoparticles biosynthesized by a mangrove-associated actinobacterium Streptomyces olivaceus (MSU3)

The present study was undertaken to biosynthesize zinc oxide nanoparticles (ZnONPs) using a mangrove-associated actinobacterium Streptomyces olivaceus (MSU3) under in vitro conditions. The synthesized ZnONPs were structurally characterized through UV, FT-IR, TG-DTA, XRD, SEM and EDX analysis. Analysis of biosynthesized ZnONPs in UV-Vis spectroscopy showed presence of functional groups between the wavelengths 325 and 380 nm. FT-IR analysis showed the functional groups, such as halo bromide (C-Br), alkyne (C≡C), carboxylic acid (O-H), nitro (N-O), fluoro (C-F), alkene (C=C) and aromatic (R-C-H) groups, respectively, within the wave numbers between 614.30 and 3074.41 cm^-1. The crystalline poly-dispersed quasi spherical nature of ZnONPs expressed the average particle size of 37.9 nm with the 2θ values of 11.802-37.885°. Antibacterial activity of ZnONPs showed pronounced inhibitory zone (25 mm) and least MIC and MBC values (125 and 250 µg ml^-1) against Escherchia sp. In the antifouling study, ZnONPs strongly inhibited byssal thread formation in mussel Perna indica and recorded LC₅₀ value of 424.47 µg ml^-1. Mollusc foot adherence assay inferred that the ZnONPs effectively inhibited settlement of limpet Patella vulgata and showed minimal fouling (26.43%) at 350 µg ml^-1 and recorded LC₅₀ value of 218.77 µg ml^-1. Results of anticrustacean assay depicted that, ZnONPs had registered LC₅₀ value of 676.08 µg ml^-1 against Artemia salina nauplii. From this study, it could be concluded that an eco-friendly approach could be used to open a new avenue for biosynthesis of ZnONPs from a mangrove associated actinobacterium S. olivaceus (MSU3) in antifouling studies.