To characterize and optimize the productivity of melanin using an extremotolerant actinobacterium, Dietzia schimae NM3, for the first time. 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. The purified melanin showed similar peak to the standard melanin (SIGMA) at 3.5 min in HPLC, and C=O bands, NH2, 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, CuSO4 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. 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.

中文翻译：

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新特性黑色素色素的生物相容性和放射防护及其在最佳乳清培养基中通过响应面分析法从白僵菌NM3产生的生物相容性和放射防护

为了首次表征和优化使用耐极端放线性放线菌迪茨氏菌NM3的黑色素的生产力。通过添加L-酪氨酸在营养肉汤和干酪乳清培养基中由D. schimae NM3产生的细胞外棕色色素。提取的黑色素通过紫外可见，HPLC和FTIR分析进行分析。测量提取的黑色素的自由基清除活性（通过DPPH）和防晒系数（SPF）。通过MTT测定黑色素的细胞毒性，并通过原子吸收光谱法测定铬酸盐的生物吸收。最后，使用Box-Behnken设计在乳清培养基中通过响应表面方法（RSM）优化了D. schimae NM3的黑色素生产。在HPLC中，纯化的黑色素在3.5分钟时显示出与标准黑色素（SIGMA）相似的峰，并且C = O谱带，NH2，CH，CN，和FTIR的芳族基团。提取的黑色素的自由基清除活性（通过DPPH）和SPF分别达到188.9％和20.22。使用MTT分析，黑色素显示出对正常人成纤维细胞（HFB）细胞培养的无毒作用。在含有乳清粉[5％（wv-1）]，L-酪氨酸2.5 gl-1，CuSO4 0.013 gl-1和pH 10.5，在32°C下孵育3天。方差分析结果表明显着的P值，模型F值和概率，而拟合度则微不足道。经过单因素优化后，营养肉汤的黑色素产量为1.2 gl-1，酪氨酸酶活性为4040 U ml-1。这是D对黑色素生产的首次报道。