Susceptibility of never-dried and freeze-dried bacterial cellulose towards esterification with organic acid

Abstract

The susceptibility of (1) never-dried and (2) freeze-dried bacterial cellulose (BC) towards organic acid esterification is reported in this work. When never-dried BC (BC which was solvent exchanged from water through methanol into pyridine) was modified with hexanoic acid, it was found that the degree of substitution (DS) was significantly lower than that of hexanoic acid modified freeze-dried BC. The crystallinity of freeze-dried BC hexanoate was found to be significantly lower compared to neat BC and never-dried BC hexanoate. This result, along with the high DS indicates that significant bulk modification occurred during the esterification of freeze-dried BC. Such results were not observed for never-dried BC hexanoate. All these evidence point towards to fact that freeze-dried BC was more susceptible to organic acid esterification compared to never-dried BC. A few hypotheses were explored to explain the observed behaviour and further investigated to elucidate our observation; the effect of residual water in cellulose, the accessibility of hydroxyl groups and the crystal structure of never-dried and freeze-dried BC on the susceptibility of cellulose fibrils to esterification, respectively. However, the investigation of these hypotheses raised more questions and we are still left with the main question; why do BC nanofibres behave differently when modifying freeze-dried BC or neverdried BC?

Cellulose nanopapers as tight aqueous ultra-filtration membranes

“…Commercial available bacterial cellulose (BC) was kindly supplied by fzmb GmbH (Bad Langensalza, Germany) in the form of wet pellicles containing 94 wt.-% water. The diameter of BC was found to be approximately 50 nm with fibril lengths of up to several micrometres [26]. Nanofibrillated cellulose was prepared by the mechanical grinding (MKZA10-15J Supermasscolloider, Masuko Sangyo Co., Kawaguchi, Japan) of chlorine free never-dried bleached birch kraft pulp (UPM-Kymmene Corporation, Pietarsaari, Finland) [19].…”

Hydroxyl accessibility in wood cell walls as affected by drying and re-wetting procedures

“…cooking during pulping. Similarly, hydroxyl accessibility to liquid water in bacterial cellulose (Lee and Bismarck 2012) and cotton cellulose (Atalla et al 2009) have been found to be higher in the never-dried state than after drying and re-wetting. When situated inside wood cell walls, however, cellulose microfibrils have hemicelluloses and lignin filling up the space between them (Salmén 2015;Salmén and Burgert 2009).…”

Upgrading flax nonwovens: Nanocellulose as binder to produce rigid and robust flax fibre preforms

“…BC is a highly crystalline nano-sized cellulose with diameter of approximately ~50 nm [17] and several micrometres in length synthesised by cellulose-producing bacteria, such as from the Acetobacter species [18]. By culturing cellulose-producing bacteria in the presence of natural fibres, BC was found to be preferentially deposited on the surface of natural fibres.…”