Optimizing enzymatic dyeing of wool and leather

This work reports on the environmental friendly enzymatic dyeing of wool and leather performed at low temperature and mild pH conditions without any dyeing auxiliaries. The substrates have been dyed with “in situ” generated pigment by means of laccase-catalyzed oxidative coupling of dye modifier 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) and dye precursor 1,3-benzenediol in a batchwise process. The process reaction variables (laccase, precursor and modifier concentrations, temperature and dyeing time) were optimized by response surface methodology using an appropriate experimental design. The temperature, precursor concentration, interaction between precursor and modifier and time are the most important factors in the dyeing process. The best-optimized wool dyeing conditions (2 h reaction time, 50 μl laccase (0.1 U), 500 mM precursor, 10 mM modifier at 40 °C) were then successfully applied onto leather material. The enzymatic-dyeing optimized process can be successfully performed on wool and leather at low temperature and mild pH obtaining different hues and depths of shades by varying the modifier concentration and time. The colouring enzymatic system has a good reusability (which has a huge advantage in terms of cost reduction) and washing durability and is comparable in terms of fastness properties to the traditional dyeing process for both wool and leather.The authors acknowledge the Portuguese Foundation for Science and Technology (FCT) for funding the project UID/CTM/00264/2019 and A. Zille contract IF/00071/2015

Influence of very low doses of mediators on fungal laccase activity - nonlinearity beyond imagination

Laccase, an enzyme responsible for aerobic transformations of natural phenolics, in industrial applications requires the presence of low-molecular substances known as mediators, which accelerate oxidation processes. However, the use of mediators is limited by their toxicity and the high costs of exploitation. The activation of extracellular laccase in growing fungal culture with highly diluted mediators, ABTS and HBT is described. Two high laccase-producing fungal strains, Trametes versicolor and Cerrena unicolor, were used in this study as a source of enzyme. Selected dilutions of the mediators significantly increased the activity of extracellular laccase during 14 days of cultivation what was distinctly visible in PAGE technique and in colorimetric tests. The same mediator dilutions increased demethylation properties of laccase, which was demonstrated during incubation of enzyme with veratric acid. It was established that the activation effect was assigned to specific dilutions of mediators. Our dose-response dilution process smoothly passes into the range of action of homeopathic dilutions and is of interest for homeopaths

Chlorination of lignin by ubiquitous fungi has a likely role in global organochlorine production

Soils and decayed plant litter contain significant quantities of chlorinated aromatic polymers that have a natural but largely unknown origin. We used cupric oxide ligninolysis coupled with gas chromatography/mass spectrometry to show that Curvularia inaequalis, a widely distributed litter ascomycete, chlorinated the aromatic rings of lignin in wood that it was degrading. In aspen wood decayed for 24 weeks, two chlorolignin fragments, 5-chlorovanillin and 2-chlorosyringaldehyde, were each found at ≈10 μg/g of wood (dry weight). These levels resemble those of similar structures generally found in unpolluted environmental samples. Fractionation of the extractable proteins followed by tandem mass spectrometric analysis showed that the colonized wood contained a previously described C. inaequalis chloroperoxidase that very likely catalyzed lignin chlorination. Chlorolignin produced by this route and humus derived from it are probably significant components of the global chlorine cycle because chloroperoxidase-producing fungi are ubiquitous in decaying lignocellulose and lignin is the earth's most abundant aromatic substance