Preparation of bacterial cellulose containing N-acetylglucosamine residues

Structure of perosamine-containing polysaccharide, a component of the sheath of Thiothrix fructosivorans

A sheath-forming and sulfur-oxidizing bacterium, Thiothrix fructosivorans, was heterotrophically cultured. The sheath, which is an extracellular microtube, was prepared by selectively removing the cells using lysozyme, sodium dodecyl sulfate, and sodium hydroxide. Solid-state (13)C-nuclear magnetic resonance (NMR) spectrum revealed that the sheath is assembled from a glycan possessing acetyl and methyl groups. When the sheath was deacetylated, the original microtube structure was lost and the sheath became soluble under acidic conditions, revealing the importance of acetyl groups in maintaining the sheath structure. Equimolar d-glucose, d-glucosamine, and l-fucose were detected in the acid hydrolysate of the sheath by gas liquid chromatography. In addition to these sugars, β-GlcN-(1→4)-Glc and unidentified sugar were detected by analyzing the hydrolysate using high-performance liquid chromatography analysis. (1)H and (13)C NMR spectroscopy was used to identify a disaccharide composed of 4-deoxy-4-aminorhamnose (perosamine, Rha4N) and fucose. N-Acetyl-perosamine prepared from the disaccharide was polarimetric and exhibited a d-configuration. The previously unidentified disaccharide was found to be α-d-Rhap4N-(1→3)-d-Fuc. According to (1)H and (13)C NMR analyses, the deacetylated sheath-forming polysaccharide was found to h have a main chain of [→4)-β-d-GlcpN-(1→4)-β-d-Glcp-(1→]n, to which disaccharide side chains of α-d-Rhap4N-(1→3)-α-l-Fucp-(1→ were attached at position 3 of Glc.

Biosynthesis of a novel polysaccharide by Acetobacter xylinum

An Acetobacter xylinum adapted to a medium containing N-acetylglucosamine (GlcNAc) has been used to prepare a novel polysaccharide containing residual GlcNAc in cellulose. The maximum amount of incorporation was found to be 4 mol% in cellulose, when a mixed medium containing 1.4% glucose (Glc) and 0.6% GlcNAc was used for the culture of A. xylinum. The resulting polysaccharide was lysozyme-susceptible. The aminosugar residue incorporated into bacterial cellulose was found to be only GlcNAc, even if galactosamine (GalN) and glucosamine (GlcN) were applied, whereas there was little effect by mannosamine (ManN). As the major component of the resulting polysaccharide was Glc residues, even if the only carbon source in the culture medium was GlcNAc, it was suggested that there must be several enzyme systems to convert GlcNAc into Glc in the bacteria. Several ammonium salts were also found to be effective for the incorporation of GlcNAc residues when the incubation system was converted to rotatory and aerobic incubation from static incubation. The amount of residual GlcNAc was remarkably increased by the addition of lysozyme-susceptible phosphoryl-chitin (P-chitin) and increased slightly with addition of P-chitin that was less lysozyme-susceptible. However, little effect was found on addition of highly substituted P-chitin.

Susceptibilities of bacterial cellulose containing N-acetylglucosamine residues for cellulolytic and chitinolytic enzymes

Detailed characterization of enzyme susceptibility of bacterial cellulose containing N-acetylglucosamine (GlcNAc) residues (N-AcGBC) which possess high susceptibility for cellulase and lysozyme and slight susceptibility for chitinase was studied. Turbidimetric lysozyme assay of N-AcGBC showed that (i) the susceptibilities of various N-AcGBCs for lysozyme were proportional to GlcNAc content, and (ii) N-AcGBC homogenates were divided into two groups based on the rate of turbidity reduction (not dependent on GlcNAc content). High reactivity of N-AcGBC for lysozyme would arise from fine microfibrils characteristic of bacterial cellulose (BC) and random distribution of GlcNAc residues in N-AcGBC because water soluble oligomers of N-AcGBC produced by lysozymic hydrolysis did not inhibit lysozyme activity; however, the random distribution of GlcNAc seemed to result in the slight susceptibility of N-AcGBC for chitinase. The rate of cellulolytic turbidity reduction of N-AcGBC was slower than that of BC, which arose from the inhibition for binding of cellulase by GlcNAc residues.