Fibers resulting from pulping of wood are negatively charged by nature. Both the cellulose and hemicelluloses contribute to the anionicity. The negative charge of cellulosic material can be reversed with the same reagent commonly used for the cationization of starch. In this study, a bleached Kraft pulp was cationized in systems with different water-miscible organic solvents. Replacing 90% of the water with isopropanol and particularly with tetrahydrofuran yielded higher degrees of substitution and increased reaction efficiency. The degree of substitution depends on the concentration of the cationization reagent in water; partially replacing water with tetrahydrofuran can simulate a higher concentration while maintaining supramolecular properties, such as crystallinity and polymer chain integrity.

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Aggregation transits from 2nd to 1st order as intermediate depletes during refolding. Better prediction in batch and pulse refolding using proposed transition model. Native model protein (sGFPmut3.1) does not aggregate with intermediates. Potential engineering tool to optimize in vitro refolding in bioprocess settings. a b s t r a c tPulse refolding is a strategy to overcome concentration dependent aggregation, assuming that aggregation is significantly suppressed under diluted conditions. When a typical 2nd or higher order aggregation kinetics is assumed, kinetics over predicted yields at low refolding concentrations. Using GFP as our model protein, we found a transition in aggregation kinetics from 2nd to 1st order when intermediates deplete from 100 to 60 mg/ml. Taking this transition into account, the model can better predict refolding yields in batch and pulse refolding strategies. This model is suited for the design of refolding processes since this deviation from 2nd or higher order aggregation was also previously observed in other proteins.

Chemical modification by attaching functional groups to lignocellulosic pulp fibers might be a strategy for improving the pulp, and thereby, paper properties. Several studies have described positive effects on paper strength properties for handsheets prepared from cationic-modified pulp or pulp fractions. This study addressed whether these effects are related to the cationic groups, e.g., by increasing electrostatic attraction and thus paper strength, or rather side effects of the chemical modification process, e.g., fiber flexibilization. To eliminate or at least minimize these side effects, only the fines fraction, which was already highly flexible, was cationized. While the addition of cationized fines affected various pulp and paper properties, most notably drainage time, no difference in strength properties was observed when comparing the addition of cationic or unmodified fines to different pulps or fractions thereof.