Purification and Physiochemical Characterization of Melanin Pigment from Klebsiella sp. GSK

Abstract

A bacterium capable of producing melanin pigment in the presence of L-tyrosine was isolated from a crop field soil sample and identified as Klebsiella sp. GSK based on morphological, biochemical, and 16S rDNA sequencing. The polymerization of this pigment occurs outside the cell wall, which has a granular structure as melanin ghosts. Chemical characterization of the pigment particles showed then to be acid resistant, alkali soluble, and insoluble in most of the organic solvents and water. The pigment got bleached when subjected to the action of oxidants as well as reductants. This pigment was precipitated with FeCl 3, ammoniacal silver nitrate, and potassium ferricynide. The pigment showed high absorbance in the UV region and decreased absorbance when shifted towards the visible region. The melanin pigment was further charecterized by FT-IR and EPR spectroscopies. A key enzyme, 4hydroxyphenylacetic acid hydroxylase, that catalyzes the formation of melanin pigment by hydroxylation of Ltyrosine was detected in this bacterium. Inhibition studies with specific inhibitors, kojic acid and KCN, proved that melanin is synthesized by the DOPA-melanin pathway.

Characterization of water-soluble dark-brown pigment from Antarctic bacterium, Lysobacter oligotrophicus

“…1B). These characteristics of absorption were consistent with the UVevisible absorption spectra of the melanins from fungi and bacteria (17,33,34). To confirm the paramagnetic properties and presence of free radicals of melanin, EPR analyses were performed (35).…”

“…The dark-brown water-soluble pigment from L. oligotrophicus was recovered from the culture by the modified method for bacterial melanin isolation (17). To identify the pigment, spectral (UVevisible, EPR and FT-IR) analyses were performed (Figs.…”

“…(14), Bacillus thuringiensis (15), Pseudomonas aeruginosa (16), Klebsiella sp. (17), and Modestobacter versicolor (18). Melanin has the ability (i) to absorb light at a wide range of wavelengths including UV and visible light (19), (ii) to scavenge toxic-free radicals and ROS (20,21), and (iii) to help certain microbial virulence and pathogenicity (22).…”

Production and Cytotoxicity of Extracellular Insoluble and Droplets of Soluble Melanin byStreptomyces lusitanusDMZ-3

“…Santos and Stephanopoulos [5] and Muñoz et al [9] reported 375 mg/L and 6 g/L of extracellular melanin production, respectively, by recombinant E. coli . Sajjan et al [6] and Youngchim et al [48] have reported the production of intracellular melanin by Klebsiella sp . and Aspergillus fumigatus, respectively.…”

“…Plenty of literature is available regarding the synthesis and production of eumelanin by different bacteria [5, 6] and fungi [7, 8]. The production of melanin by recombinant E. coli under optimized submerged bioprocess was reported by Muñoz et al [9].…”