Preparation of Absorbent Foam Based on Softwood Kraft Pulp: Advancing from Gram to Kilogram Scale

Absorbent foams were produced at both the gram scale and the kilogram scale by treating bleached softwood kraft pulp fibers to TEMPO oxidation, followed by washing, fiber disintegration, and freeze drying. Two reaction temperatures and three different dosages of primary oxidant were evaluated to find suitable oxidation conditions. It was found that the absorption and retention capacities were 50 to 70% lower for kilogram-scale foams than for gram-scale foams. SEM studies showed that the kilogram-scale foams had larger pores than the gram-scale foams; this explains the major differences in absorption and retention. The oxidation treatments performed in both scales resulted in a major increase in the amount of carboxylate groups and a major decrease in DPV, but only minor differences in these factors were found in a comparison between pulps from gram-and kilogram-scale experiments. However, the kilogram-scale dispersing equipment appeared to cause more fiber cutting, while the equipment used in the gram-scale experiments promoted the liberation of microfibrils to a greater extent. Furthermore, in both the gram- and kilogram-scale samples, a high dosage of primary oxidant and a low oxidation temperature were found to maximize the retention of liquid

Displacement washing of TEMPO-oxidized softwood kraft pulp: Effects of change in fiber properties

Bleached softwood kraft pulp fibers were treated using TEMPO oxidation at two different dosages of NaClO. A batch of non-oxidized reference pulp was also prepared with a concentration of the tracer (Na) similar to the oxidized batches. A total of 15 washing experiments were conducted and the dispersion model was used to characterize washing behavior. TEMPO oxidation resulted in a major increase in the amount of carboxylate groups in the pulps and a considerable decrease in fiber/particle size in relation to the reference pulp fibers. Oxidized fibers also had less fiber curl than reference fibers. Water retention values were greater in the oxidized pulps and the oxidized fibers exhibited major swelling during the washing operation, while reference fibers had only minor swelling. The amount of sodium in the filter cakes after washing corresponded to the amount of carboxylate groups in the pulps. Swelling of oxidized pulp fibers needs to be considered in order to describe filtration and washing. The average specific filtration resistance for all pulps in this study was in the order of 10(10)-10(11) m/kg, i.e. moderately easy to filter. The most oxidized pulp had the highest average specific filtration resistance and the lowest value for the estimated effective longitudinal dispersion coefficient, in agreement with theory

Antibacterial activity affected by the conformational flexibility in glycine-lysine-based \u3b1-helical antimicrobial peptides

Antimicrobial peptides often show broad-spectrum activity due to a mechanism based on bacterial membrane disruption, which also reduces development of permanent resistance, a desirable characteristic in view of the escalating multidrug resistance problem. Host cell toxicity however requires design of artificial variants of natural AMPs to increase selectivity and reduce side effects. Kiadins were designed using rules obtained from natural peptides active against E. coli and a validated computational algorithm based on a training set of such peptides, followed by rational conformational alterations. In vitro activity, tested against ESKAPE strains (ATCC and clinical isolates), revealed a varied activity spectrum and cytotoxicity that only in part correlated with conformational flexibility. Peptides with a higher proportion of Gly were generally less potent and caused less bacterial membrane alteration, as observed by flow cytometry and AFM, which correlate to structural characteristics as observed by circular dichroism spectroscopy and predicted by molecular dynamics calculations