Bioproduction and optimization of newly characterized melanin pigment from Streptomyces djakartensis NSS-3 with its anticancer, antimicrobial, and radioprotective properties

Abstract

Background Melanin is a natural pigment that is considered a promising biomaterial for numerous biotechnological applications across several industries. Melanin has biomedical applications as antimicrobial, anticancer, and antioxidant properties. Additionally, in the pharmaceutical and cosmetic industries, it is used in drug delivery and as a radioprotective agent. Also, melanin has environmental uses in the fields of bioremediation and the food industry. The biosynthesis of melanin pigment is an area of interest for researchers due to its multifunctionality, high compatibility, and biodegradability. Therefore, our present work is the first attempt to characterize and optimize the productivity of melanin pigment from Streptomyces djakartensis NSS-3 concerning its radioprotection and biological properties. Results Forty isolates of soil actinobacteria were isolated from the Wadi Allaqui Biosphere Reserve, Egypt. Only one isolate, ACT3, produced a dark brown melanin pigment extracellularly. This isolate was identified according to phenotypic properties and molecular phylogenetic analysis as Streptomyces djakartensis NSS-3 with accession number OP912881. Plackett–Burman experimental design (PBD) and response surface methodology (RSM) using a Box-Behnken design (BBD) were performed for optimum medium and culturing conditions for maximum pigment production, resulting in a 4.19-fold improvement in melanin production (118.73 mg/10 mL). The extracted melanin pigment was purified and characterized as belonging to nitrogen-free pyomelanin based on ultraviolet–visible spectrophotometry (UV–VIS), Fourier transform infrared (FT-IR), Raman spectroscopy, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), and NMR studies. Purified melanin demonstrated potent scavenging activity with IC50 values of 18.03 µg/mL and revealed high potency as sunscreens (in vitro SPF = 18.5). Moreover, it showed a nontoxic effect on a normal cell line (WI38), while it had a concentration-dependent anticancer effect on HCT116, HEPG, and MCF7 cell lines with IC50 = 108.9, 43.83, and 81.99 µg/mL, respectively. Also, purified melanin had a detrimental effect on the tested MDR bacterial strains, of which PA-09 and SA-04 were clearly more susceptible to melanin compared with other strains with MICs of 6.25 and 25 µg/mL, respectively. Conclusion Our results demonstrated that the newly characterized pyomelanin from Streptomyces djakartensis NSS-3 has valuable biological properties due to its potential photoprotective, antioxidant, anticancer, antimicrobial, and lack of cytotoxic activities, which open up new prospects for using this natural melanin pigment in various biotechnological applications and avoiding chemical-based drugs.

Streptomycetes as Microbial Cell Factories for the Biotechnological Production of Melanin

“…The MelC1 protein determines the effective secretion of tyrosinase in the medium, but mutants, defective in the melC1 gene and thus in the secretion of the enzyme, have also been found [ 27 ]. In the literature, several new Streptomyces strains that can produce melanin were isolated from soil samples [ 22 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 ] from different locations in Egypt, India, and Turkey, or from forest or lake environments, also eventually associated with rhizosphere or plants [ 32 , 36 , 37 , 38 , 39 ] ( Figure 3 ). Some others, instead, have been isolated from marine sediments [ 40 , 41 , 42 , 43 , 44 , 45 ] in India and China, for example, or eventually associated with marine animals like the sea cucumber Stichopus vastus [ 46 ] ( Figure 3 ).…”

“…The main reported carbon sources were glycerol, glucose, galactose, fructose, xylose, arabinose, rhamnose, raffinose, mannitol, inositol, sucrose, lactose, melibiose, starch, dextrose, and maltose [ 22 , 23 , 29 , 30 , 31 , 32 , 33 , 36 , 40 , 44 , 46 , 52 ], while both simple nitrogen sources, like ammonium sulfate, ferric ammonium citrate, sodium or potassium nitrate, ammonium chloride, ammonium nitrate, and urea, and complex nitrogen sources, like yeast extract, soybean meal, soy peptone, malt extract, beef extract, casein, casein peptone, meat peptone, and protease peptone, were exploited [ 22 , 23 , 29 , 31 , 32 , 34 , 40 ] ( Table 1 ). Many amino acids were included in different media like glycine, cystine, alanine, tryptophan, valine, leucine, proline, glutamine, aspartate, asparagine, phenyl alanine, and histidine, and L-tyrosine was often added to the medium as the first precursor of the biosynthetic pathway to enhance melanin production [ 31 , 34 , 35 , 40 , 44 , 52 ]. Salts like MgSO 4 , NaCl, FeSO 4 , K 2 HPO 4 , Na 2 HPO 4 , CaCO 3 , KCl, Na 2 S 2 O 3 , KH 2 PO 4 , CaCl 2 , NiCl 2 , FeCl 2 , MgCl 2 , ZnCl 2 , MnCl 2 , CaCl 2 , and CoCl 2 were tested as medium components, which affected the melanin production as well [ 29 , 31 , 44 ] ( Table 1 ).…”

“…Salts like MgSO 4 , NaCl, FeSO 4 , K 2 HPO 4 , Na 2 HPO 4 , CaCO 3 , KCl, Na 2 S 2 O 3 , KH 2 PO 4 , CaCl 2 , NiCl 2 , FeCl 2 , MgCl 2 , ZnCl 2 , MnCl 2 , CaCl 2 , and CoCl 2 were tested as medium components, which affected the melanin production as well [ 29 , 31 , 44 ] ( Table 1 ). Frequently, optimization experiments were performed by employing experimental design models like the one-factor-at-a-time (OFAT) method, Response Surface Methodology as Plackett–Burman design (P-BD), Central Composite Design (CCD), and face-centered central composite design [ 22 , 34 , 35 , 40 ]. Experiments were performed both on solid agar media and in liquid; in the last case, they were mainly performed in shake flasks except for only one case in which batch fermentations were run in a 2.5 L fermenter [ 23 ] ( Table 1 ).…”

Number of melanin-synthesising microorganisms under mineral fertilisation and liming of Albebeluvisoil

“…Melanins are the oldest biological pigments synthesised by representatives of all kingdoms of life (Zhdanova & Vasilevskaya, 1988). They are known for their ability to absorb broad-spectrum radiation, serve as an antioxidant, a photoprotector that effectively absorbs and dissipates solar radiation in the form of heat, a sorbent that chelates metals and binds organic compounds, and an organic semiconductor (Barreto et al, 2023;El-Zawawy et al, 2024). Specifically, A.S. Abd-El-Aziz et al (2024), for melanin from the black fungus Curvularia soli AS21 ON076460, found antimicrobial, antiviral, and antitumour activity.…”