Volume 9 Issue 2

Boric acid was employed to improve the homogeneity and mechanical properties of a composite based on cellulose fibres and polyvinyl alcohol (PVOH). The influence of boric acid, under different pH values, on the mechanical properties cellulose fibres (handsheets) was investigated. The presence of the boric acid, under alkaline conditions, further improved the mechanical properties of the handsheets. A composite based on PVOH and cellulose fibres was prepared in the presence of boric acid and glycerol, a plasticizer. The employment of the boric acid, under alkaline conditions, was necessary to obtain a homogenous composite. The morphology of the final product was analysed by SEM, and their tensile properties were measured.

Chemical and enzymatic modifications intended to improve the reactivity of dissolving pulp rapidly decrease its yield. In this study, a beating post-treatment intended to increase the reactivity of bamboo dissolving pulp was investigated. Beating post-treatment can create microfibrils on the surface of fibers. The reactivity of unrefined bamboo dissolving pulp prepared via pre-hydrolysis and a subsequent kraft cooking and Op-H-P (oxygen delignification enhanced with H2O2 and sodium hypochlorite) bleaching process was very low. The reactivity increased drastically as the Canadian standard freeness (CSF) of the bamboo dissolving pulp was decreased (i.e., the degree of beating increased). The CSF decreased to 236 mL from its original, higher freeness. The average fiber width was larger and the curling and kink indexes were lower in the pulp of CSF 236 m L compared to those of pulps with greater freeness. However, there was little impact of beating on the crystallinity index of bamboo dissolving pulp.

This research involved the most widely used wood-species of veneers in Hungary (oak, ash, beech, cherry, and maple). The resulting changes in color produced at treatment temperatures between 80 and 200 °C in different treatment times were evaluated using the CIELab color stimulus evaluation system. For higher temperature treatments, a tight functional relationship was observed between the treatment time and the difference in color stimulus. Heat treatments within a temperature range above 160 °C produced visually perceptible results, while color change resulting from heat treatments at lower temperatures was almost imperceptible. For higher temperature treatment a tight functional relationship was observed between the difference in color stimulus and treatment time (r2>min. 0.84). Different tree species produced different extents of change in hue depending on the treatment parameters. Among the color components, the perceptible discoloration was mostly produced by the change in the lightness factor (L*). As the treatment temperature rose, the change in the red (a*) and yellow (b*) components was less significant regardless of the species.

A fed-batch process and high-temperature simultaneous saccharification and fermentation (SSF) process were investigated to obtain high sugar yield and ethanol concentration. Different amounts of alkali-pretreated sugarcane bagasse were added during the first 24 h. For the highest final dry matter (DM) content of 25% (w/v), a maximal glucose and total sugar concentration of 79.53 g/L and 135.39 g/L, respectively, were achieved with 8.3 FPU/g substrate after 120 h of hydrolysis. Based on the hydrolysis experiment, two processes for ethanol production from sugarcane bagasse, simultaneous saccharification and fermentation (SSF) and separate hydrolysis and fermentation (SHF), were also compared using S. cerevisiae. The results indicated that ethanol concentration and yield in the SHF were higher, while ethanol productivity (gram per unit volume and over time) was lower. For 25% substrate loading, the ethanol productivity and ethanol concentration could reach 0.38 g.L-1.h-1 and 36.25 g/L SSF in 96 h, respectively, while that of SHF could reach 0.32 g.L-1.h-1, with an ethanol concentration of 47.95 g/L in 152 h for SHF. When high-temperature simultaneous saccharification and fermentation (SSF) process was performed by using Kluyveromyces marxianus NCYC 587 at 42 °C, 42.21 g/L ethanol (with an ethanol productivity of 0.44 g.L-1.h-1) was produced with 25% dry matter content and 8.3 FPU cellulase/g substrate, which meant 16.4% more ethanol when compared with SSF of S. cerevisiae.

Fique is a biodegradable natural fiber derived from the Colombian Agavaceae family, originating in tropical America and traditionally used for the manufacture of packaging and cordages. Today, however, new uses are being developed. To meet the need for new good-quality, sustainable, low-cost construction materials for social housing, construction materials have been produced that combine different kinds of natural fibers, including fique, to improve their strength and physical properties. To assess these potential new construction materials made with fique fiber, we have characterized samples of different grammages and thicknesses manufactured using short fique fibers extracted from long fibers. We have measured the sound absorption coefficient at normal incidence in an impedance tube, air flow resistivity, and thermal conductivity as a function of grammage.

Based on traditional kinetic models of the gasification process of char, a new modified random pore model (MRP) was proposed. This model can be reduced to a traditional volume model (VM), an unreacted shrinking core model (URCM), a hybrid model (HM), and a random pore model (RPM) by varying the model parameters. Furthermore, not only is the relationship between the reaction rate and conversion rate well described by MRP, as it is in other models, but the position of the maximum reaction rate is also described, which is out of the application range of other traditional models. MRP was validated by gasification of different kinds of chars under different experimental conditions, such as in a carbon dioxide atmosphere, in the presence of water vapor, or with the addition of catalyst. The char gasification process under various conditions could be simulated by MRP with better fitting results than the traditional RPM.

Novel biosurfactant-producing strains were isolated from hydrocarbon-contaminated environments that exclusively utilize agro-waste as their primary carbon source for the expression of biosurfactants. These were quantified using various standardized methods. Among the agro-waste screened, Beta vulgaris (Beetroot) proved to be the most suitable substrate, for which the biosurfactants produced by three bacterial isolates–B. licheniformis STK01, B. subtilis STK02, and P. aeruginosa STK03–lowered the surface tension of the culture media to 30.0, 32.98, and 30.37 mN/m, respectively. The biosurfactants achieved considerable emulsification activity, particularly for heavy hydrocarbons, with the highest emulsification indices being 65.5% and 95% for anthracene and lubricant oil, respectively. The emulsion formed with lubricant oil was thermally stable even up to 50 °C for 21 days. The results showed the proficiency of the novel bacterial isolates used, as well as the suitability of solid agro-waste for biosurfactant production, thus suggesting that exclusive utilization of solid agro-waste is a promising option for use in biosurfactant production for environmental remediation. The outstanding emulsification activity and thermal stability demonstrated by the biosurfactants produced showed their potential applications in enhancing bioavailability and bioremediation of recalcitrant and hydrophobic environmental contaminants.

The cel12B gene was cloned, optimized through directed evolution using error-prone polymerase chain reaction, and then expressed in the Escherichia coli BL21 (DE3) host strain. Five mutants promoting the enzyme activities were selected. The specific activity of the best-evolved Cel16 (L20R, D37V, I108T) was improved approximately 3-fold compared to the parental enzyme. The residual enzyme activity of Cel16 retained 90% of the original when incubated at 90 °C for 2 h, which was similar to the thermostability of the wild type. In addition, the best mutant Cel16, which had two prominent mutant sites, L20R and I108T, was able to increase the cavity polarity because the side chains of arginine and threonine could form hydrogen bonds with the substrate, shrinking the enzyme cavity to some extent and therefore enhancing the enzyme activity.

This study evaluates the impact of the number of cycles of the V313 test (EN 321 2002) on the mechanical properties of 15-mm-thick OSB/3 and OSB/4. The obtained results were compared with the properties of the boards exposed to external environmental conditions. The results of the study indicate that the tested boards were characterized with a 50% decrease in static bending strength and a 70% decrease in tensile strength perpendicular to the plane. However, both types of boards met the requirements of the standard (EN 300 2006) with respect to their modulus of rupture. The method of exposing boards to outdoor conditions has a substantial influence on the change of the physico-mechanical properties of OSBs. In the boards used in this study, however, those changes occurred slower than those evoked by the V313 test, especially after an upright exposure. For these reasons, for that type of board storage, an equation was determined that can bring the property changes following the V313 test into an acceptable range to allow for the evaluation of the board properties. In the case of vertical exposure, from the second year forward, changes in the properties of the OSB/3 were similar to those presented by the boards demonstrated from the second cycle of the V313 test.

Pulp fibers have a strong tendency to form flocs in water suspensions, which may cause their undesirable distribution in the paper sheets. This flocculation can be controlled by adding, e.g., an anionic high molecular weight polyelectrolyte in the fiber suspension. The objective of this study was to investigate the effect of anionic polyelectrolytes on deflocculation kinetics, dewatering, and rheology of cellulosic suspensions. The results showed that both microfibrillated cellulose (MFC) and macroscopic pulp fibers can be dispersed using anionic polyacrylamides (APAM). The higher the molecular weight of APAM, the higher is its effect. Adsorption experiments illustrate that anionic polyelectrolytes do not strongly attach to cellulose surfaces but they can be partly entrapped or can disperse nanocellulose fibrils (increase the swelling). Based on rheological experiments, the MFC network became weaker with APAM addition. Similar to the flocculation mechanism of cellulosic materials with polymers, deflocculation is also time dependent. Deflocculation occurs very rapidly, and the maximum deflocculation level is achieved within a few seconds. When mixing is continued, the floc size starts to increase again. Also dewatering was found to be strongly dependent on the contact time with the APAMs. These results indicate that the positive effects of anionic deflocculants are quickly diminished due to shear forces, and therefore, the best deflocculating effect is achieved using as short a contact time as possible.