The interaction of cellulose with xyloglucan and other glucan-binding polymers
This thesis examines the interaction of xyloglucan, the major hemicellulosic component of type I primary plant cell walls, with cellulose. Initial attempts to form xyloglucan-cellulose complexes by in vitro association methods are described, which gave low levels of interaction, with features not similar to those found in primary wall networks. The majority of the work focusses on the use of the bacterium Acetobacter aceti ssp. xylinum (ATCC 53524), which synthesise highly pure, crystalline cellulose as an extracellular polysaccharide. Addition of xyloglucan to a cellulose-synthesising bacterial culture results in the formation of cellulose-xyloglucan networks with ultrastructural and molecular features similar to those of the networks of higher plants. Applicatioon of the bacterial fermentation system is extended to incorporate the polysaccharides glucomannan, galactomannan, xylan, mixed-linkage glucan, pectin and carboxymethylcellulose, all of which impart unique architectural and molecular effects on the composistes formed. Preliminary data on the mechanical properties of composite structures under large and small deformation conditions are also described.