Liquid-crystalline ordering in bacterial cellulose produced by Gluconacetobaсter hansenii on glucose-containing media.

This research is dedicated to the studies of the microscale morphology of bacterial cellulose (BC) obtained by means of static cultivation of Gluconacetobacter hansenii GH-1/2008. We found that the microscale morphology depended on the BC production rate that was varied by using different glucose concentrations in the cultivation medium. It was revealed that at higher production rates, BC fibrils were aligned in a liquid-crystalline-like (LC-like) order. The observed helical alignment was always left-handed. The half-periods of the helix varied from 50 µm to 150 µm depending on the cultivation conditions. The mechanical and water absorption properties of the obtained BC pellicles were measured. The former correlated mainly with the density of the samples; the latter were the best for films with layered structure, where the BC had segregated into fleece sheets separated by gaps with low density of fibrils.

Green approach for fabrication of bacterial cellulose-chitosan composites in the solutions of carbonic acid under high pressure CO2.

The functionalization of the bacterial cellulose (BC) surface with a chitosan biopolymer to expand the areas of possible applications of the modified BC is an important scientific task. The creation of such composites in the carbonic acid solutions that were performed in this work has several advantages in terms of being biocompatible and eco-friendly. Quantitative analysis of chitosan content in the composite was conducted by tritium-labeled chitosan radioactivity detection method and this showed three times increased chitosan loading. Different physicochemical methods showed successful incorporation of chitosan into the BC matrix and interaction with it through hydrogen bonds. Microscopy results showed that the chitosan coating with a thickness of around 10 nm was formed in the bulk of BC, covering each microfibril. It was found that the inner specific surface area increased 1.5 times on deposition of chitosan from the solutions in carbonic acid.

Structural organization of bacterial cellulose: The origin of anisotropy and layered structures.

In this paper, we perform a systematic analysis of the structural organization of bacterial cellulose (BC). We report four types of organization of the BC mass, produced by Gluconacetobacter hansenii that occur depending on cultivation conditions. Two of those, particularly, plywood type one and layers of micro-sized tubes were observed and described for the first time. In spherical BC particles (pellets), we found the layered structure that had previously been reported for planar geometry only. We suggest a model explaining why layers form in BC films and attempt to reveal the impact of different factors on the BC microscale morphology. We assume that the main factor that has direct impact on the type of structure formed is the rate of BC mass accumulation.