Purification, characterisation and biological activity of melanin from Streptomyces sp.

Melanins are enigmatic biological macromolecules that can be produced by plants, animals and microorganisms and are especially suited for production in fermentation broth, which is easily industrialised and requires few inputs. This research was conducted to purify, characterise and determine the biological activity of extracellular melanin extracted from Streptomyces sp. The extracellular melanin (M) was extracted from Streptomyces sp. with a yield of 1.46 g L-1. Ma, Mb, Mc and Md were fractionated from M using a Sephadex G-50 column. Ma was detected as the homogeneous component. After studying its ultraviolet-visible absorbance, infrared and electron paramagnetic resonance spectra, as well as scanning electron microscopy images, Ma was confirmed to be typical melanin. Based on its elemental analysis, Ma consisted of carbon, hydrogen, nitrogen, oxygen and sulfur, the percentages of which suggest that phaeomelanin was the main component. In addition, Ma showed significant anti-radiation and free radical scavenging activity. Thus, these results indicated that Streptomyces sp. could be a new source from which to obtain melanin. Ma might be a potential antioxidant and ultraviolet protector and could be used in cosmetics, pesticides, food and other industries.