Preparing Cuprammonium Solvent and Cellulose Solutions

Tailored oxidation of hydroxypropyl cellulose under mild conditions for the generation of wet strength agents for paper

Secondary hydroxyl groups of hydroxypropyl cellulose (HPC) are transformed into reactive carbonyl groups selectively via TEMPO-mediated oxidation in the presence of sodium hypochlorite. By using this oxidation protocol, we introduced carbonyl functions in HPC under mild conditions, with a controlled degree of oxidation (DOx) up to 2.5 and a low degradation of the polysaccharide. The effect of the concentration of sodium hypochlorite on the resulting oxidized alcohol groups has been investigated in detail. Oxidized HPC crosslinks spontaneous at room temperature and mild pH-values with a variety of amines to form water stable hydrogels. If applied on lab-made paper sheet, thermally cross-linking this polymer with amines significantly increased the wet tensile strength. The utilization of such wet strength agents could lead to new approaches in terms of recyclability and biodegradability of wet strength agents interesting for a large number of different paper grades.

Characterization of Hydrothermal Deposition of Copper Oxide Nanoleaves on Never-Dried Bacterial Cellulose

Bacterial cellulose (BC) has attracted a great deal of interest due to its green synthesis and biocompatibility. The nanoscale dimension of BC nanofibers generates an enormous surface area that enhances interactions with water and soluble components within aqueous solution. Recent work has demonstrated that BC is a versatile platform for the formation of metal/metal oxide nanocomposites. Copper oxide (CuO) is a useful material to compare nanomaterial deposition on BC with other cellulosic materials because of copper’s colorimetric reaction as it forms copper hydroxide (Cu(OH)₂) and transitions to CuO. In this research, we found that never-dried BC readily deposits CuO into its matrix in a way that does not occur on cotton, dried BC, or regenerated cellulose fibers. We conclude that hydroxyl group availability does not adequately explain our results and that intrafibrillar pores in never-dried BC nanofibers play a critical role in CuO deposition.

ISOLATION, PURIFICATION, AND PROPERTIES OF CELLULASES FROM ASPERGILLUS TERREUS AND PENICILLIUM VARIABILE

Cellulases from A. terreus and P. variabile were isolated and purified nearly 100-fold. Enzyme production reached a maximum on the seventh day of incubation. The properties and activities of the purified cellulases were studied. At constant enzyme concentration, the activity increased with the increase in substrate concentration but the percentage of the substrate hydrolyzed decreased. Of the two purified cellulases, that from A. terreus seemed to be a purer product and was tested for its homogeneity and enzymic nature. A unienzymic nature was indicated by the observation that no resolution of the enzyme could be effected by electrophoresis. Standard solubility and diffusion tests gave no indication of heterogeneity in the purified cellulase; this finding was confirmed by the presence of only one peak in both gel filtration and ion-exchange chromatography. Random splitting of α-cellulose and carboxymethylcellulose (CMC) was indicated.