Characterization of an Insoluble and Soluble Form of Melanin Produced by Streptomyces cavourensis SV 21, a Sea Cucumber Associated Bacterium

Abstract

Melanin is a widely distributed and striking dark-colored pigment produced by countless living organisms. Although a wide range of bioactivities have been recognized, there are still major constraints in using melanin for biotechnological applications such as its fragmentary known chemical structure and its insolubility in inorganic and organic solvents. In this study, a bacterial culture of Streptomyces cavourensis SV 21 produced two distinct forms of melanin: (1) a particulate, insoluble form as well as (2) a rarely observed water-soluble form. The here presented novel, acid-free purification protocol of purified particulate melanin (PPM) and purified dissolved melanin (PDM) represents the basis for an in-depth comparison of their physicochemical and biological properties, which were compared to the traditional acid-based precipitation of melanin (AM) and to a synthetic melanin standard (SM). Our data show that the differences in solubility between PDM and PPM in aqueous solutions may be a result of different adjoining cation species, since the soluble PDM polymer is largely composed of Mg2+ ions and the insoluble PPM is dominated by Ca2+ ions. Furthermore, AM shared most properties with SM, which is likely attributed to a similar, acid-based production protocol. The here presented gentler approach of purifying melanin facilitates a new perspective of an intact form of soluble and insoluble melanin that is less chemical altered and thus closer to its original biological form.

Genomic and physiological traits provide insights into ecological niche adaptations of mangrove endophytic Streptomyces parvulus VCCM 22513

“…Using AntiSMASH, in silico prediction of secondary metabolite biosynthetic gene clusters identified a total of 25 clusters with similarity to known clusters of ≥ 16%. Of those, 4 biosynthetic gene clusters including desferrioxamin, melanin, coelichelin, and isorenieratene were reported to be antioxidant and iron chelating agents (Table S6) (Hu et al 2018;Chen et al 2019;Williams et al 2019;Wibowo et al 2022). This was in agreement with the DPPH, reducing power, superoxide radical scavenging activities observed, indicating the ability of strain VCCM 22513 to produce 4 antioxidant compounds.…”

Melanin pigment of Streptomyces puniceus RHPR9 exhibits antibacterial, antioxidant and anticancer activities

“…Production of melanin from microorganisms has been an environmentally friendly approach and economical alternative to the chemical synthesis of melanin [ 6 ]. Melanins are available in different forms, such as eumelanin, pheomelanin, and allomelanins [ 7 ].…”

Synergy between Genome Mining, Metabolomics, and Bioinformatics Uncovers Antibacterial Chlorinated Carbazole Alkaloids and Their Biosynthetic Gene Cluster fromStreptomyces tubbatahanensissp. nov., a Novel Actinomycete Isolated from Sulu Sea, Philippines

“…The crude extract of S. tubbatahanensis DSD3025 T had an oily consistency with dark brown coloration due to the high pigmented melanin content ( 55 , 56 ). Initial screening using an absorbance-based assay revealed that the nature of S. tubbatahanensis DSD3025 T extract caused false-positive results and low reproducibility.…”