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High-resistance paper was manufactured by laccase-grafting of carboxymethyl cellulose (CMC) and chitosan (CPX) on Kraft pulp fiber. The reaction was mediated in the presence of laccase by one of the following polyphenols in the presence of air: gallic acid (GA), vanillic acid (VA) and catechol (1,2-DHB). Enzyme was added at constant loading (24 kg ton-1), 1% pulp consistency, 0.005% CMC, pH = 6.3 ± 0.5 and 2 mM of mediator. CPX content was assessed at two levels (0% and 0.005%). Treated pulps were analyzed by different mechanical tests (ring crush, mullen, corrugating medium test (CMT) flat crush of corrugating medium test and tension). An improvement in these parameters was obtained by biopolymer coupling and selected mediator. When using GA, three parameters increased more than 40%, while ring crush increased 120%. For the case of VA, properties were enhanced from 74% to 88% when CPX was added. For 1,2-DHB, there was not found a statistically significant difference between the results in the presence of CPX. Scanning electron microscopy, confocal microscopy, FTIR and 13C NMR were used in all papers in order to evaluate grafting. Hence, it was possible to correlate polymerization with an improvement of paper's mechanical properties. [ABSTRACT FROM AUTHOR]

Poly(ethyleneimine) (PEI) microcapsules containing laccase from Trametes hirsuta(ThL) and Trametes versicolor(TvL) were printed onto paper substrate by three different methods: screen printing, rod coating, and flexo printing. Microcapsules were fabricated via interfacial polycondensation of PEI with the cross-linker sebacoyl chloride, incorporated into an ink, and printed or coated on the paper substrate. The same ink components were used for three printing methods, and it was found that laccase microcapsules were compatible with the ink. Enzymatic activity of microencapsulated TvL was maintained constant in polymer-based ink for at least eight weeks. Thick layers with high enzymatic activity were obtained when laccase-containing microcapsules were screen printed on paper substrate. Flexo printed bioactive paper showed very low activity, since by using this printing method the paper surface was not fully covered by enzyme microcapsules. Finally, screen printing provided a bioactive paper with high water-resistance and the highest enzyme lifetime. [ABSTRACT FROM AUTHOR]

Abstract: In this paper we report on the microencapsulation of glucose oxidase from Aspergillus niger (GOx) and laccase from Trametes versicolor (TvL) with the goal of immobilizing these enzymes in paper substrates to develop biosensors and bioreactors. Despite having high encapsulation efficiency, the technique caused a severe decrease (up to 65%) in the specific activities of both enzymes once microencapsulated. Encapsulated TvL presented lower K M and V max values compared to free laccase in solution, but the K M for GOx did not change after microencapsulation. TvL was found to interact strongly with poly(ethyleneimine) (PEI) in a manner similar to that expected from an uncompetitive inhibition mechanism, and fluorescence and circular dichroism spectroscopy demonstrated that significant alteration of the enzyme''s conformation occurs in the presence of PEI, an effect of the cationic polymer that was not observed with GOx. Microencapsulation improved the thermal stability of GOx at temperatures up to 60°C due to stabilization of its active conformation but reduced the thermal stability of laccase because of the increased coordination between PEI and copper atoms in the enzyme''s active site. Preliminary GOx bioactive paper was fabricated, which could be potentially used as food packaging paper. [Copyright &y& Elsevier]

Abstract: Enzymatic bonding methods, based on laccase or peroxidase enzymes, for lignocellulosic products such as medium-density fiberboard and particleboard are discussed with reference to the increasing costs of presently used petroleum-based adhesives and the health concerns associated with formaldehyde emissions from current composite products. One approach is to improve the self-bonding properties of the particles by oxidation of their surface lignin before they are fabricated into boards. Another method involves using enzymatically pre-treated lignins as adhesives for boards and laminates. The application of this technology to achieve wet strength characteristics in paper is also reviewed. [Copyright &y& Elsevier]