Degradation of Toxic Dye and Antimicrobial and Free Radical Potential of Environmental Benign Zinc Oxide Nanoparticles.

Several industries have become major contributors to waterbody contamination due to the improper removal of dyes and effluents into water bodies. Due to their carcinogenic properties and low biodegradability, dye degradation is a considerable danger to people, animals, and the oceanic environment. As part of this study, Andrographis paniculata leaf extract was used as a reducing and stabilizing agent to synthesize zinc nanoparticles and degrade dyes such as methyl red and eosin. Zinc oxide nanoparticles (ZnONPs) showed a surface plasmon resonance peak at 430 nm in the UV spectrum. The FTIR result showed a band at 597.93 cm-1 that confirmed the formation of zinc nanoparticles. AFM results revealed spherical ZnONPs. The SEM results predicted an average particle size of 60 nm for crystalline particles. Biologically synthesized zinc nanoparticles exhibited greater antibacterial activity against Pseudomonas spp. and Proteus spp. but lesser activity against Klebsiella spp. and S. aureus. At 1000 µg/ml concentration, ZnONPs had the highest antioxidant activity of 45.34%. An ultraviolet-visible spectrophotometer measured dye degradation progress between 300 and 800 nm. For methyl red, the maximum absorption peak was measured at 415 nm, and for eosin, the maximum peak value was measured between 500 and 515 nm.

Microbial degradation, spectral analysis and toxicological assessment of malachite green by Streptomyces chrestomyceticus S20.

Malachite green (MG), a triphenylmethane dye is extensively used for coloring silk, aquaculture and textile industries, it has also has been reported toxic to life forms. This study aimed to investigate the biodegradation potential of MG by actinobacteria. The potent actinobacterial strain S20 used in this study was isolated from forest soil (Sabarimala, Kerala, India) and identified as Streptomyces chrestomyceticus based on phenotype and molecular features. Strain S20 degraded MG up to 59.65 ± 0.68% was studied in MSM medium and MG (300 mg l-1) and degradation was increased (90-99%) by additions of 1% glucose and yeast extract into the medium at pH 7. The treated metabolites from MG by S20 characterized by FT-IR and GC-MS. The results showed MG has been degraded into nontoxic compounds evaluated by (1) phytotoxic assay on Vigna radiata, (2) microbial toxicity on Staphylococcus aureus, Bacillus subtilis, Micrococcus luteus, Streptococcus sp. and Escherichia coli, (3) cytotoxicity assay in a human cell line (MCF 7). The toxicity studies demonstrated that the byproducts from MG degradation by S. chrestomyceticus S20 were no toxic to plants and microbes and less toxic to human cells as compared to the parent MG. Perhaps this is the first work reported on biodegradation of MG by S. chrestomyceticus which could be a potential candidate for the removal of MG from various environments.