Biosynthesis Of Bacterial Cellulose-synthetic Copolymer Containing N-acetylglucosamine Residus

With coconut-water as the main culture medium, bacterial cellulose-synthetic copolymer containing N-acetylglucosamine residus (GlcNAc-BC) were obtained by culturing Acetobacter xylinum (A.x) in medium consisting of various ratios sucrose and GlcNAc in this paper. The structure and properties of these GlcNAc-BCs were measured. And the added carbon sources during the process of their biosynthesis were also studied.Pellicles were harvested after being incubated statically for 3 d. Compared with the yield of pure BC (4.9 g/L), yield of GlcNAc-BCs decreased. GlcNAc-BCs showed no significant changes on crystallinity, but their water holding capacity increased remarkably which was 163 in the medium containing 1.4% sucrose and 0.6% GlcNAc compared to 133 in the control. The max weight loss temperature and molecular weight of products both decreased when the added sucrose/GlcNAc ratio ranged from 2.0:0 to 1.0:1.0, but increased with the ratio ranged from 1.0:1.0 to 0:2.0. The alteration of the products'properties maybe was caused by modification of structure of BC. The ultrafine reticular structure and changes of meshes after modification could be seen by SEM. FTIR results sugested that GlcNAc was incorporated into the cellulose ribbons because of the absorption at 1650cm-1 and 1560cm-1.A comparative analysis during the culture process of A.x in the control medium and the medium containing GlcNAc has been made. pH of the control medium increased to 4.04 after decreasing to 3.84 in the first 2d, but increased gradually after keeping almost unchanged in the first 3d in the other medium. Yield of the dry films and content of sugar in both mediums increased rapidly and decreased remarkably respectively in the first 3d, then changed slowly. And the consumption of sugar kept always more slowly and yield of dry films kept always lower for the medium containing GlcNAc.Compared with always no GlcNAc in the control medium, content of GlcNAc in the other medium was achieved after keeping almost unchanged in the first 2d. The experimental results suggested that the bacteria was propagated largely in the first 3d, and the production rate of BC by A.x in the medium containing GlcNAc was more slowly than the control. Furthermore, the amount of GlcNAc residus in GlcNAc-BCs increased remarkably in the first 2d, and kept nearly contant later, it suggested that the bacteria used GIcNAc during the intital propagation.