Melanin

Henson, Joan M.

doi:10.1002/3527600035.bpol1008

Cited by 7 publications

(4 citation statements)

References 89 publications

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“…The complex nature and the exceptive isolation make them difficult to characterize, and their molecular structures have not yet been fully identified. Chemical analyses and spectroscopic methods including ultraviolet–visible (UV–VIS), Fourier transform infrared (FT–IR), electron spin resonance (ESR), and solid-state nuclear magnetic resonance (NMR) are usually used to reveal structural information of the polymers [9]. Recent research on natural bioactive colorants and antioxidants as multifunctional additives has increased because of consumer interest in nutritional and healthy food [10].…”

Section: Introductionmentioning

confidence: 99%

Comparison of Antioxidant Activities of Melanin Fractions from Chestnut Shell

Yao

2016

Molecules

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Chestnut shell melanin can be used as a colorant and antioxidant, and fractionated into three fractions (Fr. 1, Fr. 2, and Fr. 3) with different physicochemical properties. Antioxidant activities of the fractions were comparatively evaluated for the first time. The fractions exhibited different antioxidative potential in different evaluation systems. Fr. 1, which is only soluble in alkaline water, had the strongest peroxidation inhibition and superoxide anion scavenging activity; Fr. 2, which is soluble in alkaline water and hydrophilic organic solvents but insoluble in neutral and acidic water, had the greatest power to chelate ferrous ions; and Fr. 3, which is soluble both in hydrophilic organic solvents and in water at any pH conditions, had the greatest hydroxyl (¨OH) and 1,1-diphenyl-2-picryl-hydrazyl (DPPH¨) radicals scavenging abilities, reducing power, and phenolic content. The pigment fractions were superior to butylated hydroxytolune (BHT) in¨OH and DPPHs cavenging and to ethylene diamine tetraacetic acid (EDTA) in the Fe 2+ -chelation. They were inferior to BHT in peroxidation inhibition and O 2¨´s cavenging and reducing power. However, BHT is a synthetic antioxidant and cannot play the colorant role. The melanin fractions might be used as effective biological antioxidant colorants.

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Section: Introductionmentioning

confidence: 99%

Comparison of Antioxidant Activities of Melanin Fractions from Chestnut Shell

Yao

2016

Molecules

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“…Melanins are polymeric pigments found in most biological groups [ 1 ]. These compounds have diverse functions, mostly related to stress protection from physical and chemical factors.…”

Section: Introductionmentioning

confidence: 99%

Biosynthesis of catechol melanin from glycerol employing metabolically engineered Escherichia coli

et al. 2016

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BackgroundMelanins comprise a chemically-diverse group of polymeric pigments whose function is related to protection against physical and chemical stress factors. These polymers have current and potential applications in the chemical, medical, electronics and materials industries. The biotechnological production of melanins offers the possibility of obtaining these pigments in pure form and relatively low cost. In this study, Escherichia coli strains were engineered to evaluate the production of melanin from supplemented catechol or from glycerol-derived catechol produced by an Escherichia coli strain generated by metabolic engineering.ResultsIt was determined that an improved mutant version of the tyrosinase from Rhizobium etli (MutmelA), could employ catechol as a substrate to generate melanin. Strain E. coli W3110 expressing MutmelA was grown in bioreactor batch cultures with catechol supplemented in the medium. Under these conditions, 0.29 g/L of catechol melanin were produced. A strain with the capacity to synthesize catechol melanin from a simple carbon source was generated by integrating the gene MutmelA into the chromosome of E. coli W3110 trpD9923, that has been modified to produce catechol by the expression of genes encoding a feedback inhibition resistant version of 3-deoxy-d-arabino-heptulosonate 7-phosphate synthase, transketolase and anthranilate 1,2-dioxygenase from Pseudomonas aeruginosa PAO1. In batch cultures with this strain employing complex medium with 40 g/L glycerol as a carbon source, 1.21 g/L of catechol melanin were produced. The melanin was analysed by employing Fourier transform infrared spectroscopy, revealing the expected characteristics for a catechol-derived polymer.ConclusionsThis constitutes the first report of an engineered E. coli strain and a fermentation process for producing a catechol melanin from a simple carbon source (glycerol) at gram level, opening the possibility of generating a large quantity of this polymer for its detailed characterization and the development of novel applications.

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“…Melanins constitute a diverse class of aromatic polymers synthesized by organisms from most biological groups [ 1 ]. The biological functions of this class of compounds are various and mainly related to protection from environmental stresses [ 2 ].…”

Section: Introductionmentioning

confidence: 99%

Metabolic engineering of Escherichia coli to optimize melanin synthesis from glucose

et al. 2013

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BackgroundNatural aromatic polymers, mainly melanins, have potential and current applications in the cosmetic, pharmaceutical and chemical industries. The biotechnological production of this class of compounds is based on tyrosinase-dependent conversion of L-tyrosine and other aromatic substrates into melanins. The purpose of this work was to apply metabolic engineering for generating Escherichia coli strains with the capacity to synthesize an aromatic polymer from a simple carbon source.ResultsThe strategy was based on the expression in E. coli of the MutmelA gene from Rhizobium etli, encoding an improved mutant tyrosinase. To direct the carbon flow from central metabolism into the common aromatic and the L-tyrosine biosynthetic pathways, feedback inhibition resistant versions of key enzymes were expressed in strains lacking the sugar phosphotransferase system and TyrR repressor. The expressed tyrosinase consumed intracellular L-tyrosine, thus causing growth impairment in the engineered strains. To avoid this issue, a two phase production process was devised, where tyrosinase activity was controlled by the delayed addition of the cofactor Cu. Following this procedure, 3.22 g/L of melanin were produced in 120 h with glucose as carbon source. Analysis of produced melanin by Fourier transform infrared spectroscopy revealed similar characteristics to a pure eumelanin standard.ConclusionsThis is the first report of a process for producing melanin from a simple carbon source at grams level, having the potential for reducing production cost when compared to technologies employing L-tyrosine as raw material.

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Melanin

Abstract: Introduction Historical Outline Occurrence and Structure Fungi Animals Other Organisms Function Synthesis Precursors Pathways Enzymes, Genes and their R… Show more

Cited by 7 publications

References 89 publications

Comparison of Antioxidant Activities of Melanin Fractions from Chestnut Shell

Comparison of Antioxidant Activities of Melanin Fractions from Chestnut Shell

Biosynthesis of catechol melanin from glycerol employing metabolically engineered Escherichia coli

Metabolic engineering of Escherichia coli to optimize melanin synthesis from glucose

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