A Streptomyces lusitanus DMZ-3 strain with potential to synthesize both insoluble and soluble melanins was detected. Melanins are quite distinguished based on their solubility for varied biotechnological applications. The present investigation reveals the enhanced production of insoluble and soluble melanins in tyrosine medium by a single culture. Streptomyces lusitanus DMZ-3 was characterized by 16S rRNA gene analysis. An enhanced production of 5.29 g/L insoluble melanin was achieved in a submerged bioprocess following response surface methodology. Combined interactive effect of temperature (50°C), pH (8.5), tyrosine (2.0 g/L), and beef extract (0.5 g/L) were found to be critical variables for enhanced production in central composite design analysis. An optimized indigenous slant culture system was an innovative approach for the successful production (264 mg/L) of pure soluble melanin from the droplets formed on the surface of the culture. Both insoluble and soluble melanins were confirmed and characterized by Chemical, reactions, UV, FTIR, and TLC analysis. First time, cytotoxic study of melanin using brine shrimps was reported. Maximum cytotoxic activity of soluble melanin was Lc50-0.40 µg/mL and insoluble melanin was Lc50-0.80 µg/mL.

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A thermo tolerant, feather-degrading, newly isolated actinobacterial strain Streptomyces minutiscleroticus DNA38 was investigated for its ability to produce keratinase. Maximum production (283.4 IU) of keratinase by Streptomyces minutiscleroticus DNA38 in starch chicken feathers medium under submerged bioprocess was observed at optimized conditions of pH 9.0 of the medium and 45 °C incubation temperature. Further, an enhanced production (435.8 IU) of keratinase was achieved employing response surface methodology. Combined interactive effect of starch (7.50 g/L), yeast extract (0.74 g/L) and chicken feathers (7.50 g/L) were found to be the critical process variables for enhanced production under central composite design. Chicken feathers showed a direct action and addition of starch and yeast extract to the medium proved effective for a significant increase in the production of keratinase. The purified keratinase was monomeric and had a molecular mass of 29 kDa. The enzyme activity was significantly inhibited after pH 9.0 and temperature 50 °C.