Although most of the Ascomycetes present DHN-melanin, some reports suggest that A. nidulans does not produce this type of melanin. In this study, we analyzed the pigment extracted from highly melanized strains (MEL1 and MEL2) of Aspergillus nidulans to determine the type of melanin present in this fungus. Our results showed that the pigment produced by MEL1 and MEL2 mutants possesses physical and chemical properties and UV- and IR-spectra very similar to synthetic DOPA-melanin. The characterization of this pigment in terms of its degradation products indicated the presence of indolic units, which were also found in synthetic DOPA-melanin. The analyses of the elemental composition showed that the pigment extracted from these mutants has a high percentage of nitrogen and, therefore, it cannot be DHN-melanin, which presents only trace of nitrogen. This observation was confirmed in the test with tricyclazole because this inhibitor of DHN-melanin biosynthesis did not suppress pigment production in the MEL1 and MEL2 strains. On the other hand, in a medium containing tropolone, an inhibitor of DOPA-melanin biosynthesis, the dark pigmentation of the colonies was not observed indicating that this compound inhibited melanin production in these strains. Taken together, the results obtained in this study indicate that melanin produced by these mutants is DOPA type, representing the first report on characterization of this type of melanin in A. nidulans.

Production of the microbial pigments is one of the emerging fields of research due to a growing interest of the industry for safer products, easily degradable and eco-friendly. Fungi constitute a valuable source of pigments because they are capable of producing high yields of the substance in the cheap culture medium, making the bioprocess economically viable on the industrial scale. Some fungal species produce a dark-brown pigment, known as melanin, by oxidative polymerization of phenolic compounds, such as glutaminyl-3,4-dihydroxybenzene (GDHB) or catechol or 1,8-dihydroxynaphthalene (DHN) or 3,4-dihydroxyphenylalanine (DOPA). This pigment has been reported to act as "fungal armor" due to its ability to protect fungi from adverse conditions, neutralizing oxidants generated in response to stress. Apart from the scavenging activity, melanin exhibits other biological activities, including thermoregulatory, radio-and photoprotective, antimicrobial, antiviral, cytotoxic, anti-inflammatory, and immunomodulatory. Studies have shown that the media composition and cultivation conditions affect the pigment production in fungi and the manipulation of these parameters can result in an increase in pigment yield for large-scale pigment production. This chapter presents a comprehensive discussion of the research on fungal melanin, including the recently discovered biological activities and the potential use of this pigment for various biotechnological applications in the fields of biomedicine, dermocosmetics, materials science, and nanotechnology.

The conversion of biomass into ethanol using fast, cheap, and efficient methodologies to disintegrate and hydrolyse the lignocellulosic biomass is the major challenge of the production of the second-generation ethanol. This revision describes the most relevant advances on the conversion process of lignocellulose materials into ethanol, development of new xylose-fermenting strains of Saccharomyces cerevisiae using classical and modern genetic tools and strategies, elucidation of the expression of some complex industrial phenotypes, tolerance mechanisms of S. cerevisiae to lignocellulosic inhibitors, monitoring and strategies to improve fermentation processes. In the last decade, numerous engineered pentose-fermenting yeasts have been developed using molecular biology tools. The increase in the tolerance of S. cerevisiae to inhibitors is still an important issue to be exploited. As the industrial systems of ethanol production operate under non-sterile conditions, microbial subpopulations are generated, depending on the operational conditions and the levels of contaminants. Among the most critical requirements for production of the second-generation ethanol is the reduction in the levels of toxic by-products of the lignocellulosic hydrolysates and the production of low-cost and efficient cellulosic enzymes. A number of procedures have been established for the conversion of lignocellulosic materials into ethanol, but none of them are completely satisfactory when process time, costs, and efficiency are considered.

Melanins are black or brown pigments of high molecular weight formed by oxidative polymerization of phenolic or indolic compounds. They are found in organisms of all phylogenetic kingdoms, showing a broad spectrum of biological roles, including thermoregulation, chemoprotection, camouflage and sexual display. 1) These pigments are not essential for fungal growth and development, but have been reported to act as "fungal armor" because of the ability of the polymer to protect these microorganisms against harmful environmental conditions such as UV radiation, temperature extremes, hydrolytic enzymes, metals or plant defense mechanisms. [2][3][4][5][6][7] The effect of melanin enhancing the survival of fungi can be mainly due to its function as an extracellular redox buffer which can neutralize oxidants generated by environmental stress. 8) Wang and Casadevall 9) observed that melanized Cryptococcus neoformans cells survived the action of nitrogen-and oxygen-derived oxidants approximately 10-fold better than did non-melanized cells, suggesting that melanin contributes to virulence by protecting pathogens against free radicals generated immunologically. Studies on oxidative damage have shown that melanin in Wangiella dermatidis and Alternaria alternata appeared to confer cellular redox properties similar to those conferred by melanin upon C. neoformans. 10,11) Hoogduijn et al. 12) observed that melanin protects melanocytes and keratinocytes from the induction of DNA strand breaks by hydrogen peroxide, indicating that this pigment has an important antioxidant role in the skin.In the last decades, skin cancer has been increasing alarmingly due to chronic exposure to UV light and certain environmental chemicals. The major cause of DNA damage induced by these agents is the production of reactive oxygen species (ROS) and free radicals. 13,14) Substances acting as antioxidants, i.e., reactive oxygen and radical scavengers, protect cells from ROS-mediated DNA damage, which can result in mutation and subsequent carcinogenesis. 15,16) Various studies have demonstrated that melanins act as antioxidants and suggest its use as a raw cosmetic material to minimize light-and toxin-induced tissue destruction. 1,17) In this context, fungal melanin is of considerable biotechnological interest because it can be produced for low cost on a large scale compared with industrially-produced melanin, making its use as an antioxidative agent in cosmetic formulations economically advantageous. Taking this information into account, in the present study we assessed the antioxidant activity of the melanin pigment extracted from A. nidulans fungus in order to determine its possible utilization in the pharmaceutical industry. RESULTS AND DISCUSSIONWe first assessed the antioxidant activity of synthetic melanin, which was used as a control in the study because of its recognized activity as a reactive oxygen species (ROS) scavenger 5) As shown in Tables 1 and 2, the oxidation of 5-thio-2-nitrobenzoic acid (TNB) by hydrogen peroxide (H 2 O 2 ) and h...