Chemical degradation and characterization of bacterial cellulose under different conditions

Cellulose which is composed of ringed D-glucose monomers with β-1,4 glycosidic bond is the structural component of green plants, algae, and oomycetes. Bacterial cellulose is a secondary metabolite secreted by a variety of bacteria strains such as Acetobacter genera, Rhizobium, Sarcina, and Agrobacterium. Gluconacetobacter xylinum which is formerly as known Acetobacter xylinum is the most studied organism in cellulose production. Acetobacter genera produce cellulose pellicles and ribbons that are formed by microfibrils. Bacterial cellulose has an ultrafine network structure besides having ribbon-like microfibrils. The reticulated three-dimensional network structure of BC endows it with significant wet tensile strength, the great capability of holding water, and remarkable stability of suspension alongside being permeable, flexible, elastic, and durable. Therefore, it is widely used in the food industry, textile industry, electronic devices, drug delivery, tissue engineering, and surgical materials. The degradation of bacterial cellulose can be chemically, mechanically, and/or enzymatically. As a result of the degradation, bacterial cellulose is reduced in size up to the nanoscale. Bacterial cellulose, cellulose nanofibers (CNFs), and cellulose nanocrystals (CNCs) are the main nanocellulose types. In this study, the purpose is the chemical degradation of bacterial cellulose, which is produced by Gluconacetobacter xylinus FC01 strain, under different conditions including solvent pretreatment, liquid nitrogen degradation, autoclave pretreatment, and sulphuric acid degradation. The degraded samples are characterized by SEM, TEM, AFM, FT-IR, and DSC. The nanofibril structures were observed by SEM. According to TEM results, spherical nanocrystals and nanofibrils can be observed. The average length and width of samples ranged between 312.12-700 nm, and 9.09-27.27 nm. AFM images indicated 90% autoclave pretreated sample degraded into nanocrystals, 65% and 40% acid treated samples degraded into nanofibrils, and solvent pretreated with 40% acid with autoclave treated sample degraded into spherical nanocrystals. FT-IR demonstrated that OH stretching, C=C vibration, C-OH bending of samples changed due to the structural deformations. The crystallization and melting point showed distinct alterations due to the structural changes in the samples.