Structural aspects of the interaction of mannan-based polysaccharides with bacterial cellulose

Interactions between cellulose and glucomannan/galactomannans have been studied through molecular and ultrastructural analysis of composites formed by deposition of cellulose from Acetobacter aceti ssp.,xylinum into solutions containing either glucomannan or galactomannans of varying Man:Gal ratio.C-13 NMR suggests that unsubstituted mannan segments can bind to cellulose by undergoing a conformational transition to an extended 2-fold form. Konjac glucomannan induces a coalescence of cellulose fibrils and a dramatic reduction of crystallinity: low galactose galactomannans also show these trends. The inferred mannan/cellulose sandwich structure may underlie the densification processes which can accompany mannan-containing secondary cell wall formation. Medium galactose galactomannans additionally form cross-links of varying lengths between cellulose fibrils and show evidence for self-association. The presence of cellulose fibrils promotes network formation from galactomannan solutions under conditions where this would not normally occur. The principles of interaction between cellulose and mannan-based polymers at both molecular and ultrastructural levels are discussed in the context of plant cell wall design and assembly. (C) 1998 Elsevier Science Ltd. All rights reserved.