The natural phenolic compounds syringaldehyde and vanillin were compared to the synthetic mediators 1-hydroxybenzotriazole, violuric acid and promazine in terms of boosting efficiency in a laccase-assisted biobleaching of eucalyptus kraft pulp. Violuric acid and 1-hydroxybenzotriazole revealed to be the most effective mediators of the bioprocess. Nevertheless, laccase-syringaldehyde system also improved the final pulp properties (28% delignification and 63.5% ISO brightness) compared to the process without mediator (23% and 61.5% respectively), in addition to insignificant denaturation effect over laccase. The efficiency of the biobleaching process was further related to changes in non-conventionally used optical and chromatic parameters of pulp, such as (L*), chroma (C*) and dye removal index (DRI) showing good correlation. Adverse coupling reactions of the natural phenolic mediators on pulp lignin were predicted by electrochemical studies, demonstrating the complexity of the laccase-mediator reaction on pulp.
A bioprocess for machine washable wool, combining the advantages of both protease and transglutaminase in a simultaneous enzymatic treatment has been developed. This process reduced the felting tendency of woven wool fabrics by 9% at the expense of only 2% weight and tensile strength loss. In contrast to previously described protease-based processes for shrink resistant wool, the anti-felting properties achieved in the simultaneous enzymatic treatment produced insignificant fibre damage, confirmed also by scanning electron images of the fabrics.
G-protein-coupled receptors are integral membrane proteins which constitute the largest family of signal transduction molecules participating in the majority of normal physiological processes. G-protein-coupled receptors are responsible for the control of enzyme activity, ion channels and vesicle transport, and they respond to a wide variety of stimuli, like signals involved in sensory systems such as vision, taste and olfaction, but also to a diverse set of chemical signals such as lipids, hormones, neurotransmitters, amino acids, nucleotides, peptides and proteins. This family of receptors is being widely studied because of its potential use as pharmacological targets in drug development, and recently also for its potential use in the development of novel biosensors. G-protein-coupled receptors are specifically designed to fold and function in a lipid bilayer environment, where these membrane proteins are remarkably stable and achieve their optimal performance. The currently used technology for the purification of G-protein-coupled receptors consists in their extraction from the cell membrane and solubilization into detergent micelles. A common drawback of this strategy is that G-protein-coupled receptors solubilized in typical detergents show rather poor conformational stability, which may result in relatively rapid inactivation. The poor stability of detergent-solubilized samples renders many membrane proteins biochemically intractable. This precludes the determination of a high-resolution structure and imposes severe limitations for the development of applications. Thus, the enhancement of the stability of G-protein-coupled receptors is a major issue in order to facilitate structural determination and to unravel their potential in biotechnological applications. This work provides a brief overview of some current advances in the experimental methods for stabilizing G-protein-coupled receptors that can also be extended to other types of membrane proteins.
Gonzalez, M.; Rocasalbas, G.; Francesko, A.; Torres, J.; Tzanov, T. COST 868 Workshop, Biotechnical Functionalisation of Renewable Polymeric Materials p. 29 Data de presentació: 2008 Presentació treball a congrés
This study evaluates the potential of using ultrasound to enhance the bleaching efficiency of laccase enzyme on cotton fabrics. Ultrasound of low intensity (7 W) and relatively short reaction time (30 min) seems to act in a synergistic way with the enzyme in the oxidation/removal of the natural colouring matter of cotton. The increased bleaching effect could be attributed to improved diffusion of the enzyme from the liquid phase to the fibres surface and throughout the textile structure. On the other hand inactivation of the laccase occurred increasing the intensity of the ultrasound. However, at the ultrasound power applied in the bleaching experiments the loss of enzyme activity was not significant enough to justify the use stabilizer such as polyvinyl alcohol. Furthermore, the polyvinyl alcohol appears to be a substrate for the laccase.
Calafell, M.; Diaz, C.; Hadzhiyska, H.; Gibert, J.; Daga, J.; Tzanov, T. Biocatalysis and biotransformation Vol. 25, num. 2-4, p. 336-340 DOI: 10.1080/10242420701379874 Data de publicació: 2007-03 Article en revista
Cotton fabrics were dyed with dyes generated in situ by laccase-catalyzed oxidative coupling of the colorless 2,5-diaminobenzenesulfonic acid (2,5-DABSA) and 1-hydroxyphenol (catechol). The enzymatic oxidation of the dye intermediates led to cross-coupling reaction products when the reaction was conducted with an excess of catechol. At least fourfold excess of catechol was necessary to achieve satisfactory dye fixation on cotton. Formation of the same colored product using either an equimolar ratio of the reagents or tenfold excess of catechol was observed. Most probably, homo-molecular reactions predominate over the cross-coupling at equimolar ratio of the precursors, while with an excess of catechol, the cross-coupling occurs in higher yield. The reaction was followed using UV-Vis spectroscopy, HPLC, FTIR and MALDI-TOF MS. A reaction pathway for laccase-induced cross-coupling of catechol and 2,5-DABSA yielding a major colored product was proposed.