Large amounts of agro-industrial residues generated from diverse economic activities have attracted strong industry interest on the utilization of these residues as inexpensive substrates to support the growth of microorganisms in bioprocesses.
This strategy may represent an added value to the industry and also helps in solving pollution problems, reducing or preventing their disposal in the environment [ 1 , 66 , 67 ].
Various studies have reported the successful utilization of agro-industrial residues for the production of fungal pigments. The use of corn cob powder as a substrate for production of pigments by M. In the black yeast Hortaea werneckii , it was observed that rice bran acts as the cheapest source for increased production of melanin by than wheat bran and coconut cake [ 72 ]. Wheat bran extract, L-tyrosine, and CuSO 4 represent the best combination of medium components to obtain the maximum melanin yield from the fungus A.
A study conducted in our laboratory evaluated the use of corn steep liquor, sugarcane bagasse, and molasses as nutritional source on pigment production by melanin-overproducing mutant MEL1 from A. We observed that, in the presence of 0. The supplementation of medium with molasses and sugar cane bagasse hydrolysate did not have a positive effect on pigment production but promoted an increase in the fungal growth.
These results indicate that corn steep liquor contains substances that stimulate the synthesis of pigment and it represents a low-cost fermentation medium for large-scale production of the pigment melanin by MEL1 mutant for future industrial applications [ 74 ].
Various techniques, including electron paramagnetic resonance [ 75 ], X-ray diffraction [ 76 ], infrared, ultraviolet and visible spectroscopy [ 77 ], and nuclear magnetic resonance [ 78 ], have been used to elucidate the melanin structure from different organisms. These studies have shown that fungi can produce different types of melanins by oxidative polymerization of phenolic or indolic compounds [ 11 , 27 ]. Melanin in cell walls of Basidiomycotina is derived from phenolic precursors, as glutaminyl-3,4-dihydroxybenzene GDHB or catechol.
In the parasitic fungus Ustilago maydis , polymerization of catechol dimers with the formation of fibrils of melanin was shown [ 79 ]. This fungus may use a wide array of substrates, such as D- and L-dopamine [ 81 ], homogentisic acid [ 82 ], catecholamines, and other phenolic compounds [ 83 ], maximizing its ability to produce melanin. Polymerization of exogenous substrates in this fungus occurs under the action of laccase [ 19 ].
However, it is important to emphasize that different properties are observed for melanins derived from different substrates. Comparison of the catecholamines L-dopa, methyldopa, epinephrine, and norepinephrine shows differences in term of color, yield, and thickness of the cell wall melanin layer. It was also observed that the pigments vary in the strength of the stable free radical signal detectable by EPR [ 13 , 83 ].
In the Ascomycota fungi, melanin pigment is generally synthesized from the pentaketide pathway in which 1,8-dihydroxynaphthalene DHN is the immediate precursor of the polymer, as described by Bell and Wheeler [ 11 ] based on genetic and biochemical evidence obtained from Verticillium dahliae and W.
Figure 1 shows a general model for fungal dihydroxynaphthalene DHN -melanin biosynthesis. In this pathway, the polyketide synthase PKS converts malonyl-CoA to 1,3,6,8-tetrahydroxynaphthalene 1,3,6,8-THN , which undergoes several reduction and dehydration reactions to produce scytalone, 1,3,8-trihydroxynaphthalene THN , and vermelone. A further dehydration step leads to the intermediate 1,8-dihydroxynaphthalene DHN , which is polymerized to DHN-melanin, possibly by a laccase enzyme [ 10 , 13 , 27 ].
The biosynthetic pathway of fungal dihydroxynaphthalene DHN -melanin. Scheme adapted from Ref. However, some species of this class, including Cladosporium resinae , Epicoccum nigrum , Hendersonula toruloidea , Eurotium echinulatum , Humicola grisea , and Hypoxylon archeri , do not produce this type of pigment [ 11 , 28 , 86 — 88 ].
Bull [ 89 ] identified dopachrome indole 5,6-quinone 2-carboxylic acid and melanochrome indole 5,6-quinone , which are intermediates in the DOPA-melanin pathway, in A. Other studies confirmed the indolic nature of the melanin produced by A.
In a recent study, our group characterized the pigment produced by A. The production of DOPA-melanin has also been investigated in other fungi such as Neurospora crassa [ 94 ], Podospora anserina [ 95 ], A.
A biosynthesis pathway for fungal DOPA-melanin, proposed by [ 11 ], is shown in Figure 2 , which strongly resembles the pathway found in mammalian cells, though some of the details may differ.
The biosynthetic pathway of the dihydroxyphenylalanine DOPA -melanin in fungi. In this pathway, there are two possible starting molecules, L-dopa and tyrosine. If L-dopa is the precursor molecule, it is oxidized to dopaquinone by laccase. If tyrosine is the precursor, it is first converted to L-dopa and then dopaquinone. The same enzyme, tyrosinase, carries out both steps. Dopaquinone, a highly reactive intermediate, forms leucodopachrome, which is then oxidized to dopachrome.
Hydroxylation and decarboxylation yields dihydroxyindoles, which can polymerize spontaneously to form DOPA-melanin [ 10 , 27 , 97 ]. Some fungi have more than one biosynthetic pathway of melanins. For example, Aspergillus fumigatus synthesizes DHN-melanin [ 98 ] and also produces a second type of melanin, piomelanins, from homogentisic acid by the tyrosine degradation pathway that protects the cell wall of hyphae from ROS, and gray-green DHN-melanins determine the structural integrity of the cell wall of conidia and their adhesive properties [ 99 ].
The extracellular fungal melanin, which is found in culture fluids usually in the form of granules, can be formed from some culture components, which are autoxidized or are oxidized by phenoloxidases released from the fungus during autolysis [ 10 , 11 , 27 ]. Despite the difference in their origins, melanin pigments have a number of common characteristics that allow them to fulfill their protective function.
Several biological functions of melanins are closely associated to their chemical composition and structure. The presence of unpaired electrons in the melanin structure is responsible for various properties, including antioxidant, semiconductor, optical, electronic, and radio- and photoprotective [ 19 ].
The effect of melanin enhancing the survival of fungi under adverse conditions is mainly due to its function as an extracellular redox buffer, which can neutralize oxidants generated by the fungus in response to environmental stress [ 19 ]. It has been reported that melanin contributes for virulence of C. Studies have shown that melanin of zoopathogenic and phytopathogenic fungi is essential for their parasitizing, due to its antioxidant properties [ ].
Melanin pigment extracted from several fungal species has shown the ability to scavenge free radicals reactive nitrogen and oxygen species , becoming a potential natural antioxidant. Melanins produced by Exophiala pisciphila and Aspergillus bridgeri ICTF exhibited a significant DPPH 2,2-diphenylpicrylhydrazyl radical scavenging activity comparable with that of synthetic melanin, indicating its antioxidant potential [ , ].
Melanin pigment of Fonsecaea pedrosoi has antioxidant potential by reducing Fe III to Fe II , ensuring the balance of its redox chemical microenvironment and minimizing the effect of oxidation of fundamental structures on fungal growth [ ]. Similar results were also observed for melanin from Ophiocordyceps sinensis , which proved to be an effective DPPH radical scavenger and a strong ferrous iron chelator [ ].
The chelating power of fungal melanin can be explained by various functional groups present in the structure of this pigment, which provide an array of multiple nonequivalent binding sites for metal ions [ 14 , 22 ]. It has been reported that substances acting as antioxidants protect cells from ROS-mediated DNA damage, which can result in mutation and subsequent carcinogenesis. The excess free radicals may attack cellular constituents, as the cell membrane, nucleic acid, protein, enzymes, and other biomolecules, by peroxidation, resulting in the severe damage of cell functions and subsequent serious deleterious effects on the organism [ ].
It has been reported that melanin protects melanocytes and keratinocytes from the induction of DNA strand broken by hydrogen peroxide, indicating that this pigment also has an important antioxidant role in the skin [ ].
Studies in our laboratory showed that melanin extracted from hyperpigment-productive mutant MEL1 of A. There is experimental evidence that fungal melanin may also act as an anti-aging drug, due to its action in reducing the generation of free radicals, clearing away the free radicals produced in excess, and enhancing the activities of antioxidant enzymes.
Studies have shown that one of the major causes of aging is the surplus free radicals produced during the oxidative metabolism in the human body [ ]. It was demonstrated that the melanin produced by fungus Lachnum singerianum YM significantly inhibited the formation of lipid peroxidation products and slowed down the aging process, elevating the levels of superoxide dismutase, glutathione peroxidase, and catalase and decreasing the level of malondialdehyde in mice liver and brain homogenate and serum, suggesting that this pigment could be used as a new anti-aging drug [ ].
Researches have also shown that some fungal melanin exhibits immunomodulatory activity through the inhibition of pro-inflammatory cytokine production in T lymphocytes and monocytes, as well as fibroblasts and endothelial cells [ 12 , , ].
Our studies demonstrated that melanin extracted from a highly melanized mutant MEL1 of A. These results suggest that melanin from A. Some studies have proposed that fungal melanin exhibits anti-radiation activity in vivo and in vivo and then could be explored as a probable radioprotector [ 16 , ].
Since melanin has a stable free radical population, it is thought that the radioprotective properties of this pigment result from a combination of physical shielding and quenching of cytotoxic free radicals generated by radiation [ 18 ]. Compared with the control groups, the antioxidant defense systems, such as superoxide dismutase and glutathione peroxidase activities, were improved significantly in mice of experiment groups, and the reactive oxygen species detected by malondialdehyde content were decreased significantly.
These results confirmed that fungal melanin could be used as component of photoprotective creams mainly for its free radical scavenging rather than its light absorption properties. The probable mechanisms of radioprotection by melanin appear to be modulated in pro-survival pathways, immune system, and prevention of oxidative stress.
It was reported that melanin isolated from the fungus G. This study confirmed the possible use of melanin-coated nanoparticles for protecting against radiotoxicity during radioimmunotherapy [ ]. Recent studies have demonstrated that, in addition to the ability of transferring electrons arising under the action of radiation, melanin also possesses ionic conductivity due to its ability to transform any type of radiation energy not only into heat but also use it for the maintenance of redox processes in cells [ ].
It was assumed that melanin pigments, participating in redox reactions, are able to perceive the energy of radiation UV, visible light, and radiation and convert it into useful reducing power for metabolic processes. This hypothesis is supported by the discovery of melanized fungi in soils contaminated by radioactive nuclides and areas around the damaged Chernobyl nuclear reactors, which not only survive high radiation levels but also have enhanced growth upon exposure [ 16 , 19 , , ].
Owing to its semiconductor property, melanin becomes a promising material for organic bioelectronic devices like transistors, sensors, and batteries [ ]. Fungal melanins also exhibit growth inhibitory effect against various microorganisms. The extracellular melanin isolated from S. The A. Confocal laser scanning microscopy CLSM analyses showed that the three strains formed thick and compact biofilms when grown in the absence of pigment, but the presence of A. This study suggested that A. Silver nanoparticles incorporated Yarrowia lipolytica melanin exhibited antimicrobial activity against the pathogen Salmonella paratyphi , and they were also effective at disrupting biofilms on polystyrene as well as glass surfaces [ ].
These nanoparticles displayed excellent antifungal properties toward an Aspergillus sp. The melanin-silver nanostructures with broad-spectrum antimicrobial activity against food pathogens also have potential applicability in food processing and food packaging industries [ ]. The anti-cell proliferation effect of fungal melanin in tumoral cell lines has already been demonstrated.
The evaluation of the effect of fungal melanin on non-tumor cells is also interesting because it may serve as alternative to acute in vivo toxicity testing, avoiding the indiscriminate use of animals. The melanin produced by A. Sk derived from normal human skin fibroblasts and HEK derived from human embryonic kidney cells, and no cytotoxicity was observed against the two cell lines [ ].
In our studies, the toxicity of the melanin from A. We also showed that the toxicity of A. In this study, we demonstrated that this melanin pigment did not induce gene mutations in different strains of Salmonella typhimurium used in the Ames assay. Based on these results, we suggest that the melanin produced by A. With the current knowledge about physical and chemical properties and the broad spectrum of biological activities, fungal melanins have attracted growing interest for their potential use in the fields of biomedicine, dermocosmetics, nanotechnology, and materials science.
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Zucca, E. Basso, F. Cupaioli et al. Double, M. Gerlach, V. Zecca, A. Stroppolo, A. Gatti et al. Zecca, F. Zucca, A. Albertini, E. Rizzio, and R. S8—S11, Borges, J. On the basis of the previously collected data and in view of the comparative study of the morphological, cultural and physiological characteristics of isolate No. The production of a diffusible dark brown pigment on complex organic media is so significant that it has long been regarded as a key characteristic for the identification and classification of Streptomyce s.
The method of testing melanin formation by L-DOPA as substrate is used to confirm whether the diffusible pigments produced are melanoid dark brown or merely a brown substance, especially when complex organic media are employed The experiment was conducted in 20 runs to study the effect of the selected variables on the production of melanin.
Plackett-Burman experiments showed a markedly wide variation of melanin production from 5. The relationship between a set of independent variables and melanin production is determined by a mathematical model called multiple-regression model. The data revealed that, medium volume E and potassium nitrate J are insignificant variables with zero effect 0.
Thus instead of starting with the maximum model effects, backward regression at alpha 0. Then, the model fitted for the test of significance. Statistical analysis of the response was performed which is represented in Table 3 , Supplementary Table S2.
Supplementary Table S2 and Fig. With respect to the main effect of each variables, we can see that eight variables from the seventeen different independent variable named incubation period, L-tyrosine, peptone, protease-peptone, yeast extract, K 2 HPO 4 , ferric ammonium citrate and sodium thiosulfate affect positively melanin production, where the seven variables named glycerol, MgSO 4 , NaCl, pH, temperature, agitation speed and starch affect negatively melanin production.
The significant variables with positive effect were fixed at high level and the variables which exerted a negative effect on melanin production were maintained at low level for further optimization by a face-centered central composite design.
Medium volume was maintained at low level for further optimization. A The main effects of the factors affecting melanin production, eight variables affect positively melanin production, where seven variables affect negatively melanin production, B The Pareto chart shows the amount of influence of each factor on melanin production, C Correlation between the experimented and predicted values for melanin production by Streptomyces glau cescens strain NEAE-H according to the Plackett—Burman experimental results.
The Pareto chart illustrates the order of significance of the variables affecting melanin production in Plackett-Burman experimental design Fig. It displays the absolute values of the effects, and draws a reference line on the chart. Any effect that extends past this reference line is potentially important. Pareto chart in design expert version 7. Among the tested variables, ferric ammonium citrate showed the highest positive effect by Next to ferric ammonium citrate, protease-peptone showed positive effect by Starch showed the highest negative significance by Also, predicted versus actual melanin production plot indicated that, there is a close agreement between the experimental results and theoretical values predicted by the model equation as shown in Fig.
In addition, the value of the adjusted determination coefficient Adj. This indicated a good adjustment between the observed and predicted values. A ratio greater than 4 is desirable. Our ratio of The analysis of variance ANOVA of the experimental design was calculated, and the sum of square, mean square, F -value, P -value and confidence level are given in Table 3.
The significance of each coefficient was determined by p -values, which are listed in Table 3. The Model F -value of The analysis showed that, ferric ammonium citrate O with a probability value of 0.
Here a lower value of C. The predicted residual sum of squares PRESS statistic is used as an indication of the predictive power of a model. The model shows standard deviation and mean value of 0. The face-centered central composite design was employed to study the interactions among the significant variables and also determine their optimal levels.
Results of Placket-Burman design revealed that incubation period, protease-peptone and ferric ammonium citrate were the most significant positive independent variables affecting melanin production, thus they were selected for further optimization using face-centered central composite design.
In this study, a total of 20 experiments with different combination of incubation period X 1 , protease-peptone X 2 and ferric ammonium citrate X 3 were performed and the results of experiments are presented along with predicted response and residuals in Table 4.
Concentrations of three independent variables at different coded and actual levels of the variables also presented in Table 4. The central point was repeated six times run order: 1, 3, 10, 13, 15 and The determination coefficient R 2 of the model was 0. Therefore, the present R 2 -value reflected a very good fit between the observed and predicted responses, and implied that the model is reliable for melanin production in the present study.
A lower value of C. The model shows standard deviation and mean value of 2. In order to evaluate the relationship between dependent and independent variables and to determine the maximum melanin production corresponding to the optimum levels of incubation period X 1 , protease-peptone X 2 and ferric ammonium citrate X 3 , a second-order polynomial model Equation 2 was proposed to calculate the optimum levels of these variables and defines predicted response Y in terms of the independent variables X 1 , X 2 and X 3 :.
Where Y is the response melanin production and X 1 , X 2 and X 3 are incubation period, protease-peptone and ferric ammonium citrate, respectively. The fit summary results are presented in Supplementary Table S3. The model summary statistics focus on the models that have lower standard deviation and higher adjusted and predicted R-squared; the model summary statistics of the quadratic model showed the smallest standard deviation of 2.
The three dimensional response surface curves were plotted by statistically significant model to understand the interaction of the variables and the optimal levels of each variable required for the optimal melanin production. Figure 5A represents the three dimensional plot as function of incubation period X 1 , protease-peptone X 2 on the production of melanin.
Maximum melanin production was clearly situated close to the central point of the incubation period and protease-peptone. Further increase or decrease led to the decrease in the production of melanin. Three-dimensional response surface plots for melanin production showing the interactive effects of incubation period X 1 , protease-peptone X 2 and ferric ammonium citrate X 3 when one of the variables is fixed at optimum value and the other two are allowed to vary.
The maximum pigment production was observed on 6 th day of incubation. This result was in agreement with the finding of Rani et al. In contrast, Amal et al. Quadri and Agsar 37 reported that simple nitrogen source tyrosine gave the maximum production of melanin by thermo-alkaliphilic Streptomyces followed by phenylalanine.
Tyrosine has given the maximum production when compared to complex nitrogen sources. Potassium nitrate was reported as the best nitrogen source for the experimental actinomycete isolate to produce melanin The nitrogen source utilized varies among different species of Streptomyce s.
The formation of brown color for Streptomyces isolates on peptone-yeast extract iron agar was observed by Vasanthabharathi et al. Twenty-one cultures produced a diffusible dark brown pigment on peptone-yeast extract-iron-agar, but failed to do so on synthetic tyrosine-agar.
In these cases, the growth or the production of the enzyme is not enough to be detected on synthetic tyrosine-agar Proteose peptone is enzymatic digests of protein. It is rich in peptides with the higher molecular weight. Figure 5B depicts the incubation period X 1 and ferric ammonium citrate X 3 interactions.
At moderate levels of incubation period and ferric ammonium citrate, the production of melanin was high. The graph pointed a decline in production level when the interaction was carried beyond high and low levels of incubation period and ferric ammonium citrate.
Increases in the levels of ferric reductase activity in culture supernatants of Legionella pneumophila correlated with increased pigmentation. Legionella pneumophila is one of only a small number of microorganisms in which melanin secretion has been linked to ferric reduction A study reports that iron levels can modulate the transcriptional control of melanin biosynthesis in C.
With regard to a possible mechanism for the observed effect of iron, that the expression of the hydroxylase activity of tyrosinase is dependent on a pre-reduction site of the enzyme Figure 5C plot reveals that lower and higher levels of the protease-peptone X 2 and ferric ammonium citrate X 3 support relatively low levels of melanin production. On the other hand, the maximum melanin production clearly situated close to the central point of the protease-peptone and ferric ammonium citrate.
In addition, the interaction terms between these variables were not significant, indicating that there is no significant correlation between each two variables and that they did not help much in increasing the production of melanin. In order to determine the accuracy of the model and to verify the result, an experiment under the new conditions which obtained from face-centered central composite design was preformed.
The verification revealed a high degree of accuracy of the model of It was suggested that melanin polymers constitute the building blocks of melanin granules The process of granules formation and their dimension are strongly pH dependent, where a low pH promotes the aggregate growth and a high pH induces the breakup of the granules to small particles-oligomers with a lower degree of polymerization.
This process is a consequence of the polyelectrolyte nature of melanin, and it is dependent on the ionization state of melanin groups like carboxylic, phenolic, and aminic groups as well as on the ionic strength of the environment.
The physical appearance of the purified melanin is shown in Fig. GSK One of the main tests for identifying melanin is the FTIR spectrum.
Peak observed around The N-H bending vibration peak at The peak centered at Phenolic COH stretching at The peak observed at The spectroscopic properties of the pigment extracted from Streptomyces glaucescens strain NEAE-H correlated with those of melanin produced by various microorganisms as reported previously On the basis of the above results, it was concluded that the pigment was eumelanin.
Resonances between 8. The four broad aromatic resonances at 7. Resonances between 1. SEM was used to examine the structure of melanin and the natural melanin appears to be small spheres 5. Structural order is lacking in the case of melanin produced by S. Scanning electron microscope micrographs of the extracted melanin pigment granules at different magnifications showing small spheres.
The results revealed that, the treatment IC 50 on all cells ranged from From the obtained results, it was obvious that the melanin pigment displayed strong anticancer activity against the tested cell line. It can be observed that the purified melanin pigment of Streptomyces glaucescens strain NEAE-H showed less cytotoxicity even at high concentrations with an IC 50 value The potent cytotoxic activity of melanin against HFB4 skin cancer cell line and low cytotoxicity of against normal non-cancerous cells shows that melanin pigment can be used as potential natural anticancer.
Arun et al. On the other hand, Kurian et al. The results showed that the purified melanin pigment of Streptomyces glaucescens strain NEAE-H showed good antioxidant activity. ABTS radical was quickly and effectively scavenged by the melanin pigment.
Melanin is a polymer able to donate or accept an electron. Melanin pigment interacts with free radicals and other reactive species readily due to the presence of unpaired electrons in its molecules and acts as an antioxidant, suggesting its use as a raw cosmetic material to minimize toxin-induced tissue destruction. Melanin interacts with free radicals via the simple one electron transfer processes In vitro anti-haemolytic assay using spectroscopic method was used to evaluate the effect of melanin pigment on the erythrocytes.
The results revealed that, melanin pigment exhibited considerable anti-hemolytic activity. Melanin exhibited percentage erythrocyte hemolysis of The effective anti-hemolytic activity of melanin pigment is because of the ability of phenolic compounds in neutralizing the free radicals and thereby protecting the erythrocytes membrane from destruction and lysis. Streptomyces spp. Brown to back zone of diffusible pigment around the colonies in the medium was scored as positive.
Melanin production was quantitatively analyzed by seeding the isolates selected after the primary screening into the melanin production medium peptone yeast extract iron broth. Melanin pigment production was evaluated by measuring O. The cell free supernatant was used for assay of tyrosinase activity and melanin formation.
Detailed information is reported in the Supplementary Information. The preparation of genomic DNA of the strain was conducted in accordance with the methods described by Sambrook et al. The PCR amplification reaction was performed in accordance with the methods described by El-Naggar et al. Sequencing product was deposited in the GenBank database under accession number KJ Plackett—Burman experimental design is a two factorial design, which identifies the critical environmental and nutritional variables required for elevated melanin production and is very useful for screening the most important factors with respect to their main effects A total of 17 independent assigned and two unassigned variables commonly referred as dummy variables were screened in Plackett—Burman experimental design.
Dummy variables D 1 and D 2 are used to estimate experimental errors in data analysis. Table 2 shows the seventeen different independent variables including incubation period, pH, temperature, agitation speed, medium volume, starch, glycerol, L-tyrosine, potassium nitrate, peptone, protease-peptone, yeast extract, K 2 HPO 4 , ferric ammonium citrate, sodium thiosulfate, MgSO 4 and NaCl which chosen to be screened by Plackett Burman experiment.
All trials were performed in duplicate and the average of melanin production was treated as response. Plackett—Burman experimental design is based on the first order model:. The levels and the interaction effects between various significant variables which exerted a positive effect on the melanin production were analyzed and optimized by using face-centered central composite design FCCD.
All the experiments were done in duplicate and the average of melanin production obtained was taken as the response Y. The experimental results of FCCD were fitted via the response surface regression procedure using the following second order polynomial equation:. To precipitate the melanin, the pH of the supernatant was adjusted to 2.
The purified melanin powder was first dissolved in 0. The blank control was 0. Fourier transform infrared spectroscopy FTIR is most useful for identifying the functional groups and interpretation of structure of unknown compounds. The melanin powder and KBr powder were mixed in an agate mortar and ground for a few seconds to break up the melanin and KBr lumps.
Operating parameters were: Freq HFB4 cell line was used to determine the inhibitory effects of melanin pigment on cell growth using standard 3- 4, 5 dimethythiazolyl -2, 5-diphenyl tetrazolium bromide MTT assay This colorimetric assay is based on the conversion of the yellow tetrazolium bromide MTT to a purple formazan derivative by mitochondrial succinate dehydrogenase in viable cells.
The cells were seeded in a well plate at a density of 1. After incubation, the cells were treated with different concentration of melanin pigment 1. The purified melanin exhibited the physical and chemical properties of typical melanin. Maximum melanin yield was obtained using a simple culture process, avoids the use of purified tyrosinase, expensive chemical methods or the cumbersome extraction of this polymer from animal or plant tissues.
Melanin pigment produced by Streptomyces glaucescens NEAE-H is soluble in water, it is critical for melanin to be water soluble for a better commercial potential in biotechnological applications in the pharmaceutical and cosmetic industries. How to cite this article : El-Naggar, N. Bioproduction, characterization, anticancer and antioxidant activities of extracellular melanin pigment produced by newly isolated microbial cell factories Streptomyces glaucescens NEAE-H.
Publisher's note: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. Langfelder, K. Biosynthesis of fungal melanins and their importance for human pathogenic fungi. Fungal Genet Biol 38 , — Ikeda, K. Construction of a new cloning vector utilizing a cryptic plasmid and the highly expressed melanin-synthesizing gene operon from Streptomyces castaneoglobisporus.
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