Research Articles

The hydrolytic potential of cellulases produced by Trichoderma viride, Trichoderma pseudokoningii, Trichoderma koningii, and Trichoderma reesei with addition of exogenous β-glucosidase was evaluated on cellulose of steam-pretreated Lespedeza. The T. viride enzyme achieved the highest glucose conversion (90.09%), while T. pseudokoningii cellulase achieved the highest ratio of cellobiose to glucose (4.94%) at the end of hydrolysis. Enzymatic adsorption on the substrate was evaluated on filter paper activity and β-glucosidase activity in the corresponding digest with the obtained T. cellulases. T. viride cellulase possessed an efficient adsorption-desorption on the substrate and reached the highest FPA difference (0.72 U/mL) among enzyme activities, indicating to its excellent hydrolysis capability. However, β-glucosidase in T. viride cellulase system showed close bonding on the substrate, suggesting that efficiencies of adsorption-desorption on the cellulose are different between the entire cellulase system and β-glucosidase. T. viride cellulase, with active endogenous β-glucosidase (1.60 U/mL), has compatible synergism with the additional exogenous β-glucosidase.

Calcium(II) is one of the most common metal ions in papermaking systems. However, the effect of Ca2+ on papermaking processes has not drawn much attention. The adsorption of Ca2+ from aqueous solutions onto bleached Eucalyptus globulus kraft pulp fibers was investigated. Thermodynamic results indicate that the adsorption of Ca2+ onto bleached E. globulus kraft pulp fibers was exothermic, reversible, and spontaneous. The equilibrium data followed Langmuir isotherms. The adsorption basically agrees with the ionic reaction model between carboxyl groups of fibers and Ca2+ in which the molar ratio of carboxyl to Ca2+ is close to 2:1. The binding capacity with carboxyl groups is so strong that the anionic charge of the adsorption sites in fibers can be screened, leading to decreased performance of cationic polyacrylamide for retention and drainage, Alkyl Ketene Dimer (AKD) for sizing, and cationic starch for dry strengthThe precipitation effect of Ca2+ with three kinds of dissolved and colloidal substances (sodium rosinate, sodium stearate, sodium oxalate) also was investigated. The results showed that deposits formed by Ca2+ and dissolved and colloidal substances, which could adsorb to the surfaces of fibers, would affect drainage and retention abilities of cationic polyacrylamide.

This study was aimed at determining the effects of the force loading direction on bending strength (MOR) and modulus of elasticity (MOE) in laminated wooden materials obtained in different compositions from cut veneers of Oriental beech and Lombardy poplar with thicknesses of 4 mm and 5 mm. A total of 180 experimental specimens were prepared for determining the MOR and MOE values in parallel and perpendicular directions to the glue line. The study involved a total of 6 air-dried density layer organizations of solid Oriental beech and Lombardy popular in 4 different laminate compositions and in the same dimensions, aimed at control. Polyvinyl Acetate (PVAc) and Polyurethane (PU) were used as the adhesive type in laminations with PVAc5-PU5-PVAc4-PU4. The specimens were subjected to bending strength and modulus of elasticity experiments in parallel and perpendicular directions to the glue line in accordance with the TS EN 310 standards. As a result of the statistical analysis of the data obtained at the end of the experiments, it was determined that in the laminated materials, the force loading direction in parallel or perpendicular to the glue line affected the MOR and MOE results. The best result in the laminated materials was found to be approximately 10% higher for MOR and MOE in a parallel direction to the PU4 glue line compared to the perpendicular direction.

Enzymatic hydrolysis of non-dried and dried cellulose samples having various particles size, degree of polymerization, porosity, crystalline polymorph, and content of non-crystalline domains has been studied. Regression analysis was carried out to determine contribution of various structural features of cellulose samples to their hydrolysability. It was found that particle size, degree of polymerization, and crystalline polymorph had a negligible influence on the conversion degree of cellulose into glucose under the effect of the cellulolytic enzyme. Such characteristics as the pores volume had a fair impact on the conversion degree of cellulose. Drying of the wet samples caused decreasing of the hydrolysability of cellulose due to irreversible collapse of the pores volume. The content of non-crystalline domains (Ax) in cellulose had the highest effect on the rate of enzymatic hydrolysis and average conversion degree (αa) of cellulose into glucose. A linear dependence αa = f(Ax) was established both for dried and non-dried cellulose samples.

Safe biodegradable “green” alternatives with minimal environmental and health risks have received widespread research interest. Thirty different kinds of bio-based flocculants (modified starches, modified celluloses, native chitosan, and lignin-based flocculant) were pre-tested using a simple jar test for the examination of the applicability of new organic flocculants in papermaking and in conditioning of waste activated sludge from the pulp and paper industry. Three starch-based and two cellulose-based polymers were chosen for further flocculation and filtrations tests. Key optimization parameters for the polymer were identified as the increasing of molecular weight and nitrogen content. The starch-based polymer had the best performance in both applications, but in neither of the cases did it function as well as the commercial polyacrylamide-based polymers. The importance of the molecular weight came up in the experiments. The developed starch-based polymer was cationic and had the charge density used in industry. On the other hand, although cationic flocculants are the most used in sludge conditioning, also anionic and non-ionic polymers are needed, depending on the characteristics of the sludge to be flocculated. Overall action of the tailored polymers was also studied in order to predict their potential as papermaking retention and dewatering aids.

Lignin was used as a natural adhesive to manufacture Vitis vinifera fiberboards. The fiberboards were produced at laboratory scale by adding powdered lignin to material that had previously been steam-exploded under optimized pretreatment and pressing conditions. The kraft lignin used was washed several times with an acidic solution to eliminate any contaminants and low molecular weight compounds. This research studied the effects of amounts of lignin ranging from 5% to 20% on the properties of Vitis vinifera fiberboards. The fiberboard properties evaluated were density, water resistance in terms of thickness swelling, water absorption, and the mechanical properties in terms of modulus of rupture, modulus of elasticity, and internal bond. Results showed that fiberboards made from Vitis vinifera without lignin addition had weaker mechanical properties. However, the fiberboards obtained using acid-washed kraft lignin as a natural adhesive had good mechanical and water resistance properties that fully satisfied the relevant standard specifications.

Shyzophyllum commune IBL-06 produced 367 IU/mL of laccase in solid state bioprocess of banana stalk under optimum physical and nutritional parameters. The optimum SSF conditions were рH 4.5; temperature, 35°C; inoculum size, 3mL (106-108 mL-1); moisture content, 60%; C:N ratio in the medium, 15:1 (glucose and ammonium nitrate as additional carbon and nitrogen sources, respectively), ABTS (1mM), 1 mL, and CuSO4 (1mM), 1mL. Laccase was purified 3.95-fold with specific activity of 158 U/mg by ammonium sulfate precipitation, followed by gel filtration chromatography using Sephadex G-100 column. Molecular weight of the laccase was 63 KDa on SDS-PAGE. Purified laccase had an optimum рH of 6.0 and was stable in the рH range from 6 to 7. The optimum temperature was 40 °C, and it displayed considerable stability within the range 30 to 35 °C with 24 h incubation. Km and Vmax were 0.025 mM and 80 mM/min, respectively, using ABTS as a substrate. Copper sulfate increased the activity of purified laccase when used at low concentration, but silver nitrate exerted the strongest inhibition.

Dimer acid (DA) was grafted onto lignin (EHL) to form a graft copolymer DA-g-EHL. The selection of the reaction type and the optimization of the reaction conditions for the grafting reaction were conducted through orthogonal and single factor experiments. FT-IR and thermal analysis were used to characterize the graft product. It was found that, compared with free radical grafting, DA can be grafted onto EHL more effectively by ester condensation with strongly acidic cation exchange resin as a catalyst. Under optimum reaction conditions, the increase of acid value and the yield of graft copolymer can reach about 9.3% and 83%, respectively. The application of DA-g-EHL in preparing modified phenolic aldehyde amine curing agent (PAA) was studied. Results showed that the flexibility of the epoxy resin cured by DA-g-EHL modified PAA is significant higher than that of the resin cured by EHL modified PAA. The graft of DA onto EHL may reduce the rigidity of EHL and the chain stiffness of the PAA modified by EHL.

Trametes hirsuta is an efficient lignin-degrading species due to its ability to produce laccase and Mn-dependent peroxidase. Agricultural residues represent prospective substrates for the bioconversion into fungal biomass and lignocellulolytic enzymes, but also they could be potential environmental pollutants. Evaluation of the potential of T. hirsuta to produce ligninolytic enzymes during solid-state fermentation of selected plant raw materials was the goal of the study. The highest level of laccase activity (3827.0 ± 219.0 U/L) was noted in mandarin orange peels medium, while wheat straw and glucose-enriched mandarin orange peels media were the optimum for Mn-dependent peroxidase (1971.5 ± 23.0 U/L) and versatile peroxidase (1173.0 ± 100.0 U/L), respectively. Levels of veratryl alcohol oxidation in the presence of H2O2 were similar to those in its absence during fermentation of all selected agricultural residues, and the highest values were obtained in glucose-enriched mandarin orange peels medium. The obtained results demonstrated the potential of T. hirsuta to produce ligninolytic enzymes and mineralize various plant wastes to low-molecular weight compounds that could be further used in food, feed, and other industries.

Sequential treatments of dewaxed Calamagrostis angustifolia Kom with water (60 ºC and 90 ºC), 70% ethanol, and 70% ethanol containing 0.2%, 1.0%, 2.0%, 4.0%, and 8.0% NaOH at a solid to liquid ratio of 1:25 (g/mL) at 80 ºC for 3 h yielded 36.2% soluble polysaccharides of the dry dewaxed material. The eight polysaccharide fractions obtained were comparatively studied by sugar analysis, GPC, FT-IR, 1H and 13C-NMR, and 2D-NMR (HSQC) spectroscopy. The results showed that the water-soluble polysaccharides might contain noticeable amounts of β-D-glucan, as well as some and galactoarabinoxylan. 70% ethanol-soluble polysaccharide was mainly arabinogalactan. The five alkali-soluble hemicelluloses were mainly galactoarabinoxylans. The Ara/Xyl and Ara/Gal values of H5-H8 fractions decreased with the increment of NaOH concentration from 1.0% to 8.0%. Meanwhile, the molecular weights had a declining trend from ~60,000 to ~40,000 g/mol. The smaller sized and more branched polysaccharides ed in the early stages under milder conditions, and the larger molecular sized and more linear hemicelluloses tended to be isolated under more highly alkaline conditions.