Enzymatic polymerization of sodium lignosulfonates: effect of catalysts, initial molecular weight, and mediators

The aim of this study was to investigate the effect of different parameters on the enzymatic polymerization of sodium lignosulfonates (SLS) by laccase, compared with the chemical treatment by manganese III. Different initial molecular weights of SLS (commercial SLS (17 800 Da), F1 (4300 Da), F2 (2500 Da), and F3 (2300 Da)) were tested. Size exclusion chromatography (SEC-UV), Fourier transform infrared (FT-IR) and phenolic group determination showed that SLS molecular weight increases depending on the laccase origin, the enzyme, and the substrate concentrations and the initial molecular weight of the SLS fractions. The highest molecular weight (Mw) was obtained by fungal laccases, specifically when using laccase from Trametes versicolor, while no reactivity was observed by plant laccase (laccase from Rhus vernicifera). The largest increase of Mw (108 600 Da) is reached when using SLS (17 800 Da) at 50 g/L and 30 U/mL of laccase from Trametes versicolor. The laccase polymerization of SLS can be improved by the use of a mediator. In this study, 5 mediators were studied for F1 polymerization by laccase from Trametes versicolor: acetosyringone (ASG), violuric acid (VLA), 1-hydroxy-benzotriazole (HBT), acetovanillone (ACV) and 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS). Results of F1 polymerization with mediators showed that only ASG and VLA lead to a higher molecular weight (7500 Da) compared with reactions carried without a mediator (6600 Da).

Laccase-Catalyzed Dyeing and Finishing of Textiles with Gallic Acid

Laccase from Rhus vernicifera was applied to catalyze the polymerization of gallic acid (GA) as a way of “in situ” dyeing and finishing for wool, silk, nylon, cotton and viscose fabrics. The laccase-catalyzed polymerization of GA was confirmed by the results of UV-vis spectroscopy and differential thermal analysis. The adsorption of the GA oxidation product on the fibers contributed to the color effect and functional performance of treated fabrics. The dyed fabrics exhibited gray colors with pale to medium shades, depending on fiber categories. All the dyed fabrics showed significantly enhanced UV protection performance and antioxidant activity, and the dyed wool and silk had obviously improved deodorizing ability. These improved functional properties were related to the increased quantity of aromatic rings, phenolic hydroxyl groups and carboxyl groups in the GA oxidation product adsorbed by fibers.