Spectroscopic Characterization of Natural Melanin from a Streptomyces cyaneofuscatus Strain and Comparison with Melanin Enzymatically Synthesized by Tyrosinase and Laccase

Abstract

An actinobacteria strain was isolated from Algerian Sahara soil and assigned to Streptomyces cyaneofuscatus Pridham et al. 1958 species. This strain was selected for its ability to produce melanin exopigments in liquid and solid media. Melanin synthesis was associated with tyrosinase activity and the enzyme from this strain was isolated and biochemically characterized. Synthetic melanin was then enzymatically produced using the S. cyaneofuscatus Pridham et al. 1958 tyrosinase. As this enzyme showed a higher diphenolase activity, a synthetic melanin from the enzymic oxidation of 3,4-dihydroxyphenylalanine (dopa) was obtained by the use of a Trametes versicolor (L.) Lloyd laccase for comparison. The natural and synthetic pigments were physico-chemically characterized by the use of ultraviolet (UV)-Visible, and Fourier transform infrared (FT-IR) and multifrequency electron paramagnetic resonance (EPR) spectroscopies. All the melanin samples displayed a stable free radical when analyzed by X-band EPR spectroscopy. Once the samples were recorded at Q-band EPR, a copolymer derived from a mixture of different constituents was evident in the natural melanin. All radical species were analyzed and discussed. The use of water-soluble melanin naturally produced by S. cyaneofuscatus Pridham et al. 1958 represents a new biotechnological alternative to commercial insoluble pigments.

Copper and Melanin Play a Role in Myxococcus xanthus Predation on Sinorhizobium meliloti

“…As shown in Figures 4A,B, the FT-IR spectra obtained of the solid brown pigment extracted in both samples were very similar. Moreover, these spectra exhibited several features that are identical to those described for bacterial melanins of E. coli (Chávez-Béjar et al, 2013;Mejia-Caballero et al, 2016), Lysobacter oligotrophicus (Kimura et al, 2014), Azotobacter chroococcum (Banerjee et al, 2014), Pseudomonas (Tarangini and Mishra, 2013), Streptomyces cyaneofuscatus (Al Khatib et al, 2018), Bacillus weihenstephanensis (Drewnowska et al, 2015), and soil bacteria (Tarangini and Mishra, 2014). Nevertheless, to further confirm that the pigment was melanin, the absorbance in UV-V of pigments extracted in NaOH from a pure culture of S. meliloti GR4 and a co-culture with M. xanthus following a modified version of the protocol described by Whittaker (1963) (see section "Materials and Methods" for details) was also determined.…”

A Skin‐Inspired, Interactive, and Flexible Optoelectronic Device with Hydrated Melanin Nanoparticles in a Protein Hydrogel–Elastomer Hybrid

“…The first major absorption band at 3316 cm −1 is attributed to NH and OHH bond stretching, whereas the second major band at 1636 cm −1 is attributed to the aromatic CC stretching and COO asymmetric stretching. [ 27 ] Two weak bands at 1485 and 1271 cm −1 are attributed to the phenolic COH bending and CH stretching. [ 27 ] In addition, OH liberations induce a third major absorption band in the range 600–500 cm −1 .…”

“…[ 27 ] Two weak bands at 1485 and 1271 cm −1 are attributed to the phenolic COH bending and CH stretching. [ 27 ] In addition, OH liberations induce a third major absorption band in the range 600–500 cm −1 . For the dehydrated MNPs, the observed FTIR spectrum shows a decrease in intensity and shift of the first absorption band (3316–3250 cm −1 ), which are mainly attributed to water.…”

“…These shifts of the absorption bands indicate free‐radical formation during the redox reaction when MNPs are hydrated. [ 27,28 ]…”

Melanins as Sustainable Resources for Advanced Biotechnological Applications

“…[ 171–173 ] Melanins display paramagnetic character due to free radicals in their structures (e.g., semiquinone free radicals) which absorb microwaves under magnetic fields yielding spectra characteristic of the radical species present. EPR/ESR spectroscopy is therefore a potent method of studying melanins, with reports of its use for fundamental biochemistry studies (e.g., melanin type, [ 169,174–177 ] effect of pH [ 178–180 ] ), characterising melanins from different species including bacteria ( Rubrivivax benzoatilyticus JA2, [ 121 ] Vibrio natriegens , [ 181 ] Streptomyces cyaneofuscatus [ 182 ] ), yeast ( Cryptococcus neoformans [ 167 ] ), mushrooms ( Inonotus hispidus [ 183 ] ), black soldier flies ( Hermetia illucens [ 184,185 ] ), squid ( Loligo opalescens [ 175 ] ), cuttlefish ( Sepia officinalis [ 186 ] ), and cephalopod ink sacs from the Jurassic era. [ 187 ] Ionizing irradiation changes the EPR/ESR signals of fungal melanins due to changes in the electronic structure of the melanins, which informed a fascinating study of melanized fungal cells ( Wangiella dermatitidis , Cryptococcus Neoformans and Cladosporium Sphaerospermum ) which displayed increased growth relative to nonmelanized cells after exposure to ionizing radiation.…”