الفهرس 
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Abstract
Melanin is an important pigment produced by all living organisms from eukaryotic to prokaryotic organisms. It was formed by hydroxylation and polymerization of organic compounds. Melanin has three main types; eumelanin, pheomelanin and allomelanin. In this study, a local black yeast strain, named Hortaea werneckii EGYNDA08, The obtained sequence was submitted to the Genbank and was issued an accession number of KU341734. Melanin from Hortaea werneckii EGYNDA08 was extracted and identified as DHN-melanin by different chemical, physical and molecular characterization methods.
A series of optimization processes was carried out by using DOE tools to indicate the most favorable conditions to increase the black yeast growth and melanin production. At first cultivation conditions; temperature and pH were optimized by CCD experiment to be 22°C and 6.0, respectively. In order to reduce the production cost of melanin, cheap production medium was generated., the optimum combination was estimated to be 10 g/L sugar cane molasses, 3.8 g/L corn steep liquor and 2.5 g/L malt extract, leading to increase melanin production up to 210 mg/L comparing to 30 mg/L prior to optimization. In light conditions, the production of melanin by Hortaea werneckii EGYNDA08 reached 228 mg/L compared to 160 mg/L in dark conditions.
Melanin extracted from Hortaea werneckii EGYNDA08 was found to have antimicrobial activity against some of multidrug resistance bacterial strains and against Candida albicans. The produced melanin was also reported to exhibit antioxidant activity with an IC50= 0.2 mg/ml. Moreover, DHN-melanin from Hortaea werneckii EGYNDA08 was found to have a great protective effect on the Bt-C18 of bioinsecticide produced by Bacillus thuringiensis subsp. aegypti strain C18 against direct exposure to sunlight.