Use of cellulose fibers from hemp core in fiber-cement production. Effect on flocculation, retention, drainage and product properties

The aim of this paper is to study the feasibility of using cellulose fibers obtained from an agricultural waste, hemp core (Cannabis Sativa L), through different new environmental friendly cooking processes for fiber-cement production. The physical and mechanical properties of the fiber reinforced concrete, which depend on the nature and morphology of the fibers, matrix properties and the interactions between them, must be kept between the limits required for its application. Therefore, the morphology of the fibers and how its use affects the flocculation, retention and drainage processes in the fiber-cement manufacture, and the mechanical and physical properties of the fiber-cement product have been studied. The use of pulp obtained by means of the hemp core cooking in ethanolamine at 60% concentration at 180 degrees C during 90 min resulted in the highest solids retention and the best mechanical properties among the studied hemp core pulps. (C) 2012 Elsevier B.V. All rights reserved.

Edible films from alginate-acerola puree reinforced with cellulose whiskers

Fruit purees, combined or not with polysaccharides, have been used in some studies to elaborate edible films. The present study was conducted to evaluate tensile properties and water vapor barrier of alginate-acerola puree films plasticized with corn syrup, and to study the influence of cellulose whiskers from different origins (cotton fiber or coconut husk fiber, the latter submitted to one- or multi-stage bleaching) on the film properties. The whiskers improved the overall tensile properties (except by elongation) and the water vapor barrier of the films. The films with coconut whiskers, even those submitted only to a one-stage bleaching, presented similar properties to those of films with cotton whiskers, despite the low compatibility between the matrix and the remaining lignin in coconut whiskers. This was probably ascribed to a counterbalancing effect of the higher aspect ratios of the coconut whiskers. (C) 2011 Elsevier Ltd. All rights reserved.

Two structurally discrete GH7-cellobiohydrolases compete for the same cellulosic substrate fiber

Background: Cellulose consisting of arrays of linear beta-1,4 linked glucans, is the most abundant carbon-containing polymer present in biomass. Recalcitrance of crystalline cellulose towards enzymatic degradation is widely reported and is the result of intra-and inter-molecular hydrogen bonds within and among the linear glucans. Cellobiohydrolases are enzymes that attack crystalline cellulose. Here we report on two forms of glycosyl hydrolase family 7 cellobiohydrolases common to all Aspergillii that attack Avicel, cotton cellulose and other forms of crystalline cellulose. Results: Cellobiohydrolases Cbh1 and CelD have similar catalytic domains but only Cbh1 contains a carbohydrate-binding domain (CBD) that binds to cellulose. Structural superpositioning of Cbh1 and CelD on the Talaromyces emersonii Cel7A 3-dimensional structure, identifies the typical tunnel-like catalytic active site while Cbh1 shows an additional loop that partially obstructs the substrate-fitting channel. CelD does not have a CBD and shows a four amino acid residue deletion on the tunnel-obstructing loop providing a continuous opening in the absence of a CBD. Cbh1 and CelD are catalytically functional and while specific activity against Avicel is 7.7 and 0.5 U. mg prot-1, respectively specific activity on pNPC is virtually identical. Cbh1 is slightly more stable to thermal inactivation compared to CelD and is much less sensitive to glucose inhibition suggesting that an open tunnel configuration, or absence of a CBD, alters the way the catalytic domain interacts with the substrate. Cbh1 and CelD enzyme mixtures on crystalline cellulosic substrates show a strong combinatorial effort response for mixtures where Cbh1 is present in 2: 1 or 4: 1 molar excess. When CelD was overrepresented the combinatorial effort could only be partially overcome. CelD appears to bind and hydrolyze only loose cellulosic chains while Cbh1 is capable of opening new cellulosic substrate molecules away from the cellulosic fiber. Conclusion: Cellobiohydrolases both with and without a CBD occur in most fungal genomes where both enzymes are secreted, and likely participate in cellulose degradation. The fact that only Cbh1 binds to the substrate and in combination with CelD exhibits strong synergy only when Cbh1 is present in excess, suggests that Cbh1 unties enough chains from cellulose fibers, thus enabling processive access of CelD.

Indigestible cellulose and lignin in determining feces production and apparent digestibility in horses

Four crossbred geldings were used in a randomized blocks experimental design. The objective was to study the use of the internal markers indigestible cellulose (iCEL) and indigestible lignin (iLIG), obtained in situ (cattle) or in vivo (equine) to predict nutrient apparent digestibility in horses. Treatments consisted of different methodologies to determine digestibility: direct method with total feces collection (TC), and indirect method using internal markers iCEL and iLIG obtained either by in situ incubation in bovine rumen or in vivo (IV) using the mobile nylon bag (MNB) technique in horses. Feces production was 2.80 kg in DM, and average recovery rate (p > 0.05) was 101%. Nutrient digestibility coefficient (p > 0.05) estimates were adequately predicted by iCEL and iLIG, obtained in situ or in vivo, with average values of 52.63, 54.17, 64.90, 43.73 and 98.28% for dry matter, organic matter, crude protein, neutral detergent fiber and starch, respectively. It can be concluded that iCEL and iLIG may be obtained in vivo by MNB in horses consuming a forage-concentrate diet, to predict nutrient digestibility coefficients.