Lignin-carbohydrate complexes from sisal (Agave sisalana) and abaca (Musa textilis): chemical composition and structural modifications during the isolation process.

Two types of lignins occurred in different lignin-carbohydrate fractions, a lignin enriched in syringyl units, less condensed, preferentially associated with xylans, and a lignin with more guaiacyl units, more condensed, associated with glucans. Lignin-carbohydrate complexes (LCC) were isolated from the fibers of sisal (Agave sisalana) and abaca (Musa textilis) according to a plant biomass fractionation procedure recently developed and which was termed as "universally" applicable to any type of lignocellulosic material. Two LCC fractions, namely glucan-lignin (GL) and xylan-lignin (XL), were isolated and differed in the content and composition of carbohydrates and lignin.

Obtaining biobleached eucalyptus cellulose fibres by using various enzyme combinations.

Various combinations of laccases, xylanase and cellulase were used to biobleach cellulose fibres from eucalyptus. The Trametes villosa and Myceliophthora thermophila laccases were used in combination with violuric acid (VA(TvL) system) and methyl syringate (MeS(MtL) system), respectively, as mediator. A dissimilar mode of action of the two systems was found: the VA(TvL) treatment released both hexenuronic acids and lignin, whereas the MeS(MtL) released lignin alone.

Demonstration of laccase-based removal of lignin from wood and non-wood plant feedstocks.

The ability of Trametes villosa laccase, in conjuction with 1-hydroxybenzotriazole (HBT) as mediator and alkaline extraction, to remove lignin was demonstrated during treatment of wood (Eucalyptus globulus) and non-wood (Pennisetum purpureum) feedstocks. At 50 Ug(-1) laccase and 2.5% HBT concentration, 48% and 32% of the Eucalyptus and Pennisetum lignin were removed, respectively.

On hexenuronic acid (HexA) removal and mediator coupling to pulp fiber in the laccase/mediator treatment.

Flax soda/AQ pulps were treated with different fungal laccase-mediator combinations followed by physical and chemical characterization of the pulps to obtain a thorough understanding of the laccase/mediator effects on hexenuronic acid (HexA) removal and the coupling of mediator onto pulps for fiber functionalization. Large differences were found and the presence of lauryl gallate (LG) during Trametes villosa laccase (TvL) treatment (TvL+LG) resulted in a much larger reduction of pulp-linked HexA than the combination of p-coumaric acid (PCA) and Pycnoporus cinnabarinus laccase (PcL). A major portion of LG became attached to the pulp as revealed by an increase in the kappa number and further confirmed by thioacidolysis and (1)H NMR analysis of solubilized pulp fractions.

Use of cellulases and recombinant cellulose binding domains for refining TCF kraft pulp.

The modular endoglucanase Cel9B from Paenibacillus barcinonensis is a highly efficient biocatalyst, which expedites pulp refining and reduces the associated energy costs as a result. In this work, we set out to identify the specific structural domain or domains responsible for the action of this enzyme on cellulose fibre surfaces with a view to facilitating the development of new cellulases for optimum biorefining. Using the recombinant enzymes GH9-CBD3c, Fn3-CBD3b, and CBD3b, which are truncated forms of Cel9B, allowed us to assess the individual effects of the catalytic, cellulose binding, and fibronectin-like domains of the enzyme on the refining of TCF kraft pulp from Eucalyptus globulus.

Can the laccase mediator system affect the chemical and refining properties of the eucalyptus pulp?

Application of a laccase mediator system (an L stage) to TCF and ECF bleached pulp from Eucalyptus globulus with low residual lignin content (KN(lig)1.0) provides useful information about its effects on hexenuronic acids, functional groups (carboxyl and carbonyl) and electrokinetic properties such as zeta potential and surface charge. The use of laccase from Trametes villosa in combination with the mediator 1-hydroxybenzotriazole (HBT) was found to oxidize cellulose to carbonyl groups and reduce the amount of carboxyl groups present in TCF pulp by effect of its partially removing hexenuronic acids from it.

Influence of the hexenuronic acid content on refining and ageing in eucalyptus TCF pulp.

Brightness in totally chlorine-free (TCF) pulp is more unstable than it is in elemental chlorine-free (ECF) pulp, seemingly by effect of the former containing greater amounts of oxidizable structures such as hexenuronic acids (HexA). Accelerated ageing tests involving the application of moist heat to pulp revealed that brightness reversion can be alleviated by using an effective biotechnological method involving an enzyme-mediator treatment. Thus, the joint use of laccase from Trametes villosa and the mediator hydroxybenzotrialoze (HBT) in TCF pulp removes hexenuronic acids by 23% and reduces brightness reversion by 8.

Engineering a family 9 processive endoglucanase from Paenibacillus barcinonensis displaying a novel architecture.

Cel9B from Paenibacillus barcinonensis is a modular endoglucanase with a novel molecular architecture among family 9 enzymes that comprises a catalytic domain (GH9), a family 3c cellulose-binding domain (CBM3c), a fibronectin III-like domain repeat (Fn3(1,2)), and a C-terminal family 3b cellulose-binding domain (CBM3b). A series of truncated derivatives of endoglucanase Cel9B have been constructed and characterized. Deletion of CBM3c produced a notable reduction in hydrolytic activity, while it did not affect the cellulose-binding properties as CBM3c did not show the ability to bind to cellulose.