Thermal Behavior of Bacterial Cellulose Aerogels and Cryogels

This study investigates the thermal performance of additive-free bacterial cellulose (BC) aerogels and cryogels produced by Acetobacter xylinus under controlled static cultivation conditions. The influence of supercritical CO2 (ScCO2) drying and freeze-drying on the multiscale structure and functional properties of BC materials was evaluated. Since BC is biosynthesized by a living microbial system, minor biological variations in fibril organization and network formation may occur even under standardized cultivation conditions. To minimize variability, all samples were produced, purified, and processed using identical procedures prior to drying. The materials were characterized using SEM, DSC, and Alambeta thermal analysis, while environmental temperature and relative humidity were monitored during testing. The two drying routes produced differences in fibrillar organization, accessible pore characteristics, and thermal transport. ScCO2-dried aerogels showed a more homogeneous nanofibrillar morphology, whereas the lyophilized cryogels exhibited thermal conductivity values of 0.032–0.041 W·m−1·K−1, comparable to those of the ScCO2-dried specimens (0.040–0.042 W·m−1·K−1). Overall, the results demonstrate that controlled lyophilization can produce additive-free porous BC with thermal performance comparable to ScCO2 drying under the investigated conditions. The lightweight, highly porous, fibrous character of these materials further supports their relevance for functional textile systems, including bio-based nonwoven or layered thermal-insulation structures, while lyophilization offers a comparatively simple processing route.