Behavior of Freezable Bound Water in the Bacterial Cellulose Produced by Acetobacter xylinum: An Approach Using Thermoporosimetry

Abstract

Abstract. The aim of the study is to examine thermal behavior of water within reticulated structure of bacterial cellulose (BC) films by sub-ambient differential scanning calorimetry (DSC). BC films with different carbon source, either manitol (BC (a)) or glycerol (BC (b)), were produced by Acetobacter xylinum using Hestrin and Shramm culture medium under static condition at 30±0.2°C for 3 days. BC samples were characterized by electron scanning microscopy and X-ray diffraction spectroscopy. The pore analysis was done by B.H.J. nitrogen adsorption. The pre-treated with 100% relative humidity, at 30.0±0.2°C for 7 days samples were subjected to a between 25 and −150°C-cooling-heating cycle of DSC at 5.00°C/min rate. The pre-treated samples were also hydrated by adding 1 μl of water and thermally run with identical conditions. It is observed that cellulose fibrils of BC (a) were thinner and reticulated to form slightly smaller porosity than those of BC (b). They exhibited slightly but non-significantly different crystalline features. The freezable bound water behaved as a water confinement within pores rather than a solvent of polymer which is possible to use thermoporosimetry based on Gibb-Thomson equation to approach pore structure of BC. In comparison with nitrogen adsorption, it was found that thermoporosimetry underestimated the BC porosity, i.e., the mean diameters of 23.0 nm vs. 27.8 nm and 27.9 nm vs. 33.9 nm for BC (a) and BC (b), respectively, by thermoporosimetry vs. B.H.J. nitrogen adsorption. It may be due to large non-freezable water fraction interacting with cellulose, and the validity of pore range based on thermodynamic assumptions of Gibb-Thomson theory.

Formulation of Dacarbazine-loaded Cubosomes. Part III. Physicochemical Characterization

“…These include indinavir-loaded microparticle (1,2) controlled-release baclofen tablets (3) bacterial cellulose (4), and solid state amoxicillin trihydrate (5). These drug formulation characterization approaches have been recently used for nanosuspension formulation as well (6).…”

Hierarchical growth of nickel oxyhydroxide on bacterial cellulose hydrogel: role of water channels in hydrogel to form hierarchical structure

“…The presence of hydroxyl moieties induces intense hydrogen bonding with water molecules that trap the abundant water to form BC hydrogel. It is evident that ordered layer of water is a key player in the formation of hierarchical NiOOH structure over the BC nanofiber . The never‐dried wet BC hydrogel provides a unique tunnel structure for the penetration of Ni 2+ ions.…”

“…It is evident that ordered layer of water is a key player in the formation of hierarchical NiOOH structure over the BC nanofiber. 43 The never-dried wet BC hydrogel provides a unique tunnel structure for the penetration of Ni 2+ ions. This sort of penetration and hierarchical structure was not observed in case of freeze-drying BC aerogel and carbonized aerogel ( Figure S1a-d).…”

Superabsorbent crosslinked bacterial cellulose biomaterials for chronic wound dressings

“…It has been demonstrated previously, that the amount of water lost from BC matrix to the outer environment depends on the arrangement of cellulose microfibrils [27]. As demonstrated by Kaewnopparat et al [85], only 10% of the water in BC behaves like free bulk water. Thus, most of the water molecules within the cellulose are, more or less tightly, bound to the cellulose.…”