New insights and advances on pyomelanin production: from microbial synthesis to applications

Abstract

Pyomelanin is a brown-black phenolic polymer and results from the oxidation of homogentisic acid (HGA) in the L-tyrosine pathway. As part of the research for natural and active ingredients issued from realistic bioprocesses, this work re-evaluates the HGA pigment and makes an updated inventory of its syntheses, microbial pathways, and properties, with tracks and recent advances for its large-scale production. The mechanism of the HGA polymerization is also well documented. In alkaptonuria, pyomelanin formation leads to connective tissue damages and arthritis, most probably due to the ROS issued from HGA oxidation. While UV radiation on human melanin may generate degradation products, pyomelanin is not photodegradable, is hyperthermostable, and has other properties better than the L-Dopa melanin. This review aims to raise awareness about the potential of this pigment for various applications, not only for skin coloring and protection but also for other cells, materials, and as a promising (semi)conductor for bioelectronics and energy.

Aspergillus niger as a cell factory for the production of pyomelanin, a molecule with UV-C radiation shielding activity

“…Notably, we could show that already a small amount of dissolved Pyo Fun (0.5 mg/mL) shielded the melanin-deficient strain MA93.1 significantly against the LD 90 UV-C dose of the fully pigmented wild-type strain N402. The protective effect was higher for the melanin-deficient strain, which was expected, due to its higher susceptibility toward (Lorquin et al, 2021(Lorquin et al, , 2022 Production in yeasts Yarrowia lipolytica grown on optimized medium Yarrowia lipolytica mutant strain grown on optimized medium 0.5 g per l of medium 4.5 g per l of medium (Tahar et al, 2020;Larroude et al, 2021) Production in bacteria Pseudomonas putida mutant strain grown on optimized medium Halomonas titanicae grown on optimized medium 0.35 g per l of medium 0.55 g per l of medium (Nikodinovic-Runic et al, 2009;Lorquin et al, 2021) Enzymatic production Recombinant laccase enzyme with precursor molecule 1.25 g per g of precursor molecule (Lorquin et al, 2021) Production in filamentous fungi…”

Phenolic Polymers as Model Melanins

“…EDX data suggests that all samples are mainly composed of C and O for all polymers with a trace of N present in the polyDOPA samples (similar to the XPS data), with additional traces of Ca, K, and Na from the buffer, Au (sputter coating) and Si (substrate) (Figure 4 and Figure S11, Supporting Information). Interestingly, EDX data shows that the polymers in the highly soluble fractions have higher metal ion contents (measured as relative abundance by EDX) than the low solubility fractions, polyCAT‐HS (Ca: 8.9% ± 0.1%; Na: 0.4% ± 0.1%), polyDOPA‐HS (Ca: 8.4% ± 0.1%; Na: 1.6% ± 0.9%), polyHGA‐HS (Ca: 0.3% ± 0.1%; Na: 15.3% ± 0.8%), by comparison with polyCAT‐LS (Ca: 2.1% ± 0.4%; Na: 0.1% ± 0.1%) and polyDOPA‐LS (Ca: 0.2% ± 0.1%; Na: 0.0% ± 0.0%), confirming the polyphenol's ability to bind metal ions, [ 71,72 ] a putative role for melanins in biology [ 56,73 ] and underpinning their application in energy storage. [ 74–77 ]…”

“…Various methods of polymerization of aromatics (e.g., phenols) exist, including enzymatic, [42][43][44][45][46][47] electrochemical, [48][49][50][51][52][53][54][55][56][57] oxidative, [58,59] etc. and the polymerization of phenols is the subject of an excellent review from Kobayashi and co-workers, [58,59] which examined the propensity for C-C or C-O-C bond formation which would be expected to play a role in the conductivity of the resulting polymers (polymers connected via C-C bonds akin to graphene derivatives [60] are expected to have higher electrical conductivity than polymers connected via C-O-C bonds).…”

BEYOND UNIFORMITY: Pyomelanin’s structural complexity impacts on UV shielding inPseudomonasspecies with different lifestyles

“…In a melanogenic strain of B. thuringiensis , the observed pigment provided protection against UVC radiation for an insecticidal protein, enhancing its appeal for biotechnological applications (Liu et al, 2013). Remarkably, in certain pathogenic species, melanin exhibited effective scavenging of ROS in human fibroblasts after UVA radiation and in mouse fibroblasts after UVB exposure, concurrently increasing fibroblast viability (23,24). However, many studies are focused on analyzing the impact of UVA and UVB radiation, emphasizing the role of melanin as sunscreens (17).…”