Noncytotoxic bacterial nano-melanin with immense cosmetic potential produced by <i>Bacillus infantis</i> isolated from salt pans of Marakkanam, Tamil Nadu, India

Abstract Melanin is a high molecular weight pigment derived from the oxidation of phenols, followed by the polymerization of phenols and the quinones they produce. Usually, they appear in dark brown or black color. Bacillus infantis was isolated from saltpans of Marakkanam, Tamilnadu. This strain was utilized for melanin production by screening using tyrosine basal broth, and the extracted pigment was characterized by UV-visible spectrometer and FT-IR. Notably, melanin was found to be nano size and it is confirmed by DLS analysis. The nano-sized melanin-producing strain Bacillus infantis was confirmed as non-pathogenic by testing with different antibiotics. This study also explores the sun protection factor of melanin, and this melanin shows successful outcomes. The antioxidant activity of melanin shows a wide range of radical scavenging activity by DPPH, ABTS and FRAP assays. The melanin has shown modest anti-ageing activity at the higher concentration tested. Nano melanin was found to be non-cytotoxic even in higher concentrations tested. This is the first report on melanin production by Bacillus infantis , and there is limited information available to date about melanin-producing bacteria from salt pan sediments.