RESUMO
Due to their remarkable characteristics, cellulose nanocrystals are strategic materials that has various industrial applications, and are capable of being produced from vegetable fibers derived from the discards of agricultural practices. Peanut(Arachis hypogaea L.) peel is a residue considered of low commercial value and high polluting potential that needs new applications in order to mitigate these problems. Thus, in this study the feasibility of extracting cellulose nanocrystals was investigated. Two chemical routes were followed for this extraction. In the first, the fibers were bleached before acid hydrolysis whereas mercerization was used in the second. The second route was more efficient, as it enabled the elimination of proteins and phenolic compounds, which could be confirmed through solid-state 13C nuclear magnetic resonance (NMR) that revealed no signs of lignin residues. The cellulose nanocrystals composed of mainly type I cellulose presented a high degree of crystallinity index, 75 %, a thermal stability up to 200 °C, considerable stability in suspension (zeta potential of -48.1 ± 2.1 mV), and an aspect ratio of 125. They represent options that could add value to this residue, which would ease environmental problems.
Assuntos
Arachis , Celulose , Nanopartículas , Fenômenos Químicos , Resíduos de Alimentos , HidróliseRESUMO
We report on production of novel quaternary nanocomposite films based on thermoplastic starch (TPS, 8% w/v) derived from cassava, cocoa butter, (CB, 30% wt.%), and lemongrass essential oil (LEO, 1:1) nanoemulsions reinforced with different concentrations of brewery spent grain (BSG, 5 or 10 wt.%) fibers, by continuous casting. The chemical composition, the morphological, thermal, mechanical properties, film barrier, biodegradability in the vegetable compound, in addition to the application in chocolates, have been widely studied. The addition of CB, LEO, and BSG caused relevant changes in the starch-based films, such as increased extensibility (from 2.4-BSG5 to 9.4%-BSG10) and improved barrier to moisture (2.9 and 2.4 g.mm.kPa-1 .h-1 .m-2 ). Contrastingly, the thermal stability of the starch film was slightly decreased. The biodegradability of the herein developed quaternary nanocomposite films was the same as that of TPS films, eliminating concerns on the supplementation with active ingredients that are expected to have some biocidal effect. Despite checking antimicrobial activity only by contact under the biocomposites, chocolates packed with the films were well accepted by consumers, especially the samples of white chocolate stored in the BSG5 biocomposite. Overall, this new approach towards quaternary active, biodegradable films produced in a pilot-scale lamination unit was successful in either improving or at least maintaining the essential properties of TPS-based films for food packaging applications, while providing them with unique features and functionalities. PRACTICAL APPLICATION: This contribution relates to new approach toward quaternary films produced in a pilot-scale lamination unit. It relates to sustainability as it is both biodegradable and based on plant biomass, as well as produced via a clean, through high-yield process. The four components of the edible films we developed provide it with good in properties performance, as both a passive barrier (i.e. purely physical), and active, related to the sensory attributes of food, essential to be applied in food packaging. The valorization of a BSG also adds to the relevance of our contribution within the circular bioeconomy framework.
Assuntos
Cymbopogon/química , Gorduras na Dieta/análise , Grão Comestível/química , Manihot/química , Nanocompostos/química , Óleos Voláteis/química , Amido/química , Fibras na Dieta/análise , Embalagem de AlimentosRESUMO
Xylanases have important applications in industry. Immobilization and stabilization of enzymes may allow their reuse in many cycles of the reaction, decreasing the process costs. This work proposes the use of a rational approach to obtain immobilized commercial xylanase biocatalysts with optimized features. Xylanase NS50014 from Novozymes was characterized and immobilized on glyoxyl-agarose, agarose-glutaraldehyde, and agarose-amino-epoxy support and on differently activated chitosan supports: glutaraldehyde-chitosan, glyoxyl-chitosan, and epoxy-chitosan. Two different chitosan matrices were tested. The best chitosan derivative was epoxy-chitosan-xylanase, which presented 100% of immobilization yield and 64% of recovered activity. No significant increase on the thermal stability was observed for all the chitosan-enzyme derivatives. Immobilization on glyoxyl-agarose showed low yield immobilization and stabilization degrees of the obtained derivative. The low concentration of lysine groups in the enzyme molecule could explain these poor results. The protein was then chemically modified with ethylenediamine and immobilized on glyoxyl-agarose. The new enzyme derivatives were 40-fold more stable than the soluble, aminated, and dialyzed enzyme (70 degrees C, pH 7), with 100% of immobilization yield. Therefore, the increase of the number of amine groups in the enzyme surface was confirmed to be a good strategy to improve the properties of immobilized xylanase.
Assuntos
Quitosana/química , Endo-1,4-beta-Xilanases , Enzimas Imobilizadas , Sefarose/química , Animais , Endo-1,4-beta-Xilanases/química , Endo-1,4-beta-Xilanases/metabolismo , Estabilidade Enzimática , Enzimas Imobilizadas/química , Enzimas Imobilizadas/metabolismo , Géis/química , Concentração de Íons de Hidrogênio , TemperaturaRESUMO
Trypsin was immobilized on chitosan gels coagulated with 0.1 or 1 M NaOH and activated with glutaraldehyde or glycidol. The derivatives were characterized by their recovered activity, thermal (40, 55 and 70 degrees C) and alkaline (pH 11) stabilities, amount of enzyme immobilized on gels for several enzyme loads (8-14 mg(protein)/g(Gel)) and compared to agarose derivatives. Enzyme loads higher than 14 mg(protein)/g(Gel) can be immobilized on glutaraldehyde derivatives, which showed 100% immobilization yield and, for loads up to 8 mg(protein)/g(Gel), 100% recovered activity. Activation with glycidol led to lower immobilization yields than the ones obtained with glutaraldehyde, 61% for agarose-glyoxyl (AgGly) with low grade of activation and 16% for the chitosan-glyoxyl (ChGly), but allowed obtaining the most stable derivative (ChGly), that was 660-fold more stable than the soluble enzyme at 55 and 70 degrees C-approximately threefold more stable than AgGly. The ChGly derivative presented also the highest stability during incubation at pH 11. Analyses of lysine residue contents in soluble and immobilized trypsin indicated formation of multipoint bonds between enzyme and support, for glyoxyl derivatives.