Bacterial Cellulose: A Model for Deconstructing Cellulose Native Structure.

摘要

Advancements in colloidal and polymer chemistry have expanded the commercial applications of cellulose to include the development of high strength composite films for the production of energy efficient liquid displays, high-fidelity biosensors and acoustic diaphragms for high quality audio speakers. Additionally, cellulose is the most abundant polymer on earth making it the most logical candidate precursor for the replacement of fossil fuels. Although the commercial promise of cellulose is high, the establishment of cellulose as a global commodity is significantly hindered by the inefficiencies in cellulose liberation and processing. The current model associated with cellulose liberation from lignin and hemicellulose relies on the use of highly basic reagents resulting in significant alterations to cellulose native structure. The research detailed here examines the inherent properties of cellulose in its most native state using bacterial cellulose (BC) synthesized by Gluconacetobacter hansenii (G. hansenii) strain ATCC 23769 as a model; with the intent of improving cellulose liberation and saccharification techniques through the understanding of the biochemical complexities of in vivo cellulose. Previously characterized for the protection BC provides G. hansenii against mechanical, chemical and physiological stress, the degree of resistance BC affords G. hansenii against antibiotics is investigated here. The addition of kanamycin (kan) at a concentration of 50 microg ml--1 to wild type cultures of G. hansenii results in the selection of high cellulose producing phenotypes. Furthermore, it is demonstrated that when cultured in the presence of 5% (v/v) cellulase, a complete loss in kan resistance is observed in wild type cultures of G. hansenii. The stability of BC structure when exposed to mechanical, chemical and thermal influence is also examined. An 88% drop in the intensity of the 1i0 peak (16.4°) of BC x-ray diffractograms is observed when BC samples are prepared by cryo-homogenization and pressed into film using 670 MPa of pressure, resulting in a 21% reduction in calculated crystallinity. A 100% improvement in the saccharification efficiency of cyro-homogenized BC despite a negligible change in observed degree of polymerisation (DP n) from 606 &