Natural protection of the Bacillus thuringiensis-based biopesticides from inactivation by the UV component of the cosmic rays constitutes a big challenge to environmentalists, health concerned groups, and industry. Melanin pigment produced by a variety of microbes has the capabilities of protecting these types of biopesticides. A black melanin produced by a locally isolated strain of the yeast Hortaea werneckii EGYNDA08 possesses the qualities of a sun protectant agent. This UV bio-protectant increased the killing potency of a locally isolated B. thuringiensis subsp. aegypti (Bt-C18)-based biopesticide ninefold upon feeding the first instar larvae of the cotton leaf worm, Spodoptera littrolis. This black melanin was extracted, characterized, and exposed to different optimization process for the purpose of enhancing its productivity. The optimization process employed medium engineering techniques to generate a suitable cheap production medium not only at bench-scale level but also at the bioreactor level. These optimization techniques have led to increase the melanin produced by the local isolate of Hortaea werneckii EGYNDA08 up to 228 mg/l compared to 8 mg/l prior to optimization. This study concluded that black yeast melanin could be used at a wide range as a potential green alternative for the conventional chemically based sunscreens that currently used to protect biopesticides from inactivation by the cosmic rays.

Melanin is a pervasive pigment that synthesized in all living organisms from prokaryotes to eukaryotes by polymerization or hydroxylation of organic compounds. Melanin is important for survival of fungi in extreme conditions, like as high salinity that are typical for hypersaline environment. The ascomycetous black yeast Hortaea werneckii was isolated from such environment was identified as a potential source of melanin. Melanin has different applications in many fields like as cosmetics and pharmaceutical industries. In this study, Hortaea werneckii was isolated from hypersaline Egyptian habitat on enrichment media. Our study was carried out to study the ability of Hortaea to produce melanin and optimization of culture conditions that enhance the production. Detection of different genes responsible for production of melanin from the isolate was also studied. The optimum cultivation conditions that led to a maximum melanin yield was found to be; temperature 22oC and pH 6.0 achieving 48.5 mg/L. Also, extracted melanin showed antimicrobial activity against different pathogens like as, Staphylococcus sp, Streptococcus pyogenes, Methicillin resistant Staphylococcus aureus (MRSA), Bacillus subtilis, Erwinia carotovora.

Following publication of the original article (Saleh et al. 2018), the authors flagged that the article had published with an incomplete version of affiliation 2; ' Agriculture research center (ARC)' had been erroneously omitted from the affiliation.The affiliation has since been updated in the published article, and the corrected affiliation may be found in this erratum.