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

[Display omitted] •Plywood-type organization and layers of “tubes” were found in bacterial cellulose.•Layered structures were found in bacterial cellulose pellets.•The formation of layers in bacterial cellulose is mediated by the fibrils laying rate. 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.