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Purpose To characterize and optimize the productivity of melanin using an extremotolerant actinobacterium, Dietzia schimae NM3, for the first time. Methods An extracellular brown pigment produced by D. schimae NM3 in the nutrient broth and cheese whey medium by adding L-tyrosine. The extracted melanin was analyzed by UV-visible, HPLC, and FTIR assays. The radical scavenging activity (by DPPH) and sun protection factor (SPF) of the extracted melanin were measured. The melanin cytotoxicity was assayed by MTT and chromate biosorption was measured by atomic absorption spectroscopy. Finally, melanin production by D. schimae NM3 was optimized by response surface methodology (RSM) using Box-Behnken design in the whey medium. Result The purified melanin showed similar peak to the standard melanin (SIGMA) at 3.5 min in HPLC, and C=O bands, NH 2 , CH, C-N, and aromatic groups by FTIR. The radical scavenging activity (by DPPH) and SPF of the extracted melanin were obtained 188.9% and 20.22, respectively. Using MTT assay, the melanin revealed non-toxic effect on the normal human fibroblast (HFB) cell culture. The melanin yield 790 mg l −1 , and tyrosinase activity 3400 U ml −1 were obtained in the medium contained whey powder [5% (w v −1 )], L-tyrosine 2.5 g l −1 , CuSO 4 0.013 g l −1 , and pH 10.5, incubated at 32 °C for 3 days. The ANOVA results indicated significant P -value, model F -value, and probability, with insignificant lack of fit. After optimization with mono-factors, the nutrient broth came up with melanin yield as 1.2 g l −1 and tyrosinase activity as 4040 U ml −1 . Conclusion This is the first report of melanin production by D. schimae NM3 and this natural melanin showed valuable biological properties such as high antioxidant activity and radioprotection (SPF) and the biocompatibility to human cell line.

annals of microbiology

Biocompatibility and radioprotection by newly characterized melanin pigment and its production from Dietzia schimae NM3 in optimized whey medium by response surface methodology