ABSTRACT
Steam explosion after sulphur dioxide impregnation of wood chips is an effective method for improving the enzymatic digestibility of cellulose in the softwood Pinus radiata. Digestibility of pretreated fiber was progressively increased by altering the conditions of steam explosion. With increasing digestibility, there was an observed increase in fiber porosity as measured by the solute exclusion technique. Accessible pore volume and accessible surface area to a 5-nm dextran probe positively correlated with both 2- and 24-h digestion yields from pretreated fiber. The increase in accessibility was probably the result of hemicellulose extraction and lignin redistribution. A subsequent loss in accessibility, brought about by structural collapse or further lignin redistribution, resulted in a corresponding loss in digestibility. It appears that steam explosion increases cellulose digestibility in P. radiata by increasing fiber porosity.
ABSTRACT
By using the techniques of methylation analysis, uronic acid degradation, partial hydrolysis, and periodate oxidation, th structure of the capsular polysaccharide from Klebsiella serotype K70 has been investigated. Nuclear magnetic resonance was used extensively to characterize fragments obtained as a result of the various degradation procedures. The existence of a linear, hexasaccharide repeating unit having a 1-carboxyethylidene group attached to a 2-linked alpha-L-rhamnosyl residue in every second repeating unit has been demonstrated.
Subject(s)
Klebsiella/immunology , Polysaccharides, Bacterial , Cell Wall/immunology , Chemical Phenomena , Chemistry , Hydrolysis , Klebsiella/ultrastructure , Magnetic Resonance Spectroscopy , Methylation , Oligosaccharides , Polysaccharides, Bacterial/immunology , Serotyping , Uronic AcidsABSTRACT
Klebsiella D36 capsular polysaccharide has been investigated by methylation, Smith-periodate oxidation and partial hydrolysis techniques. The structure was found to consist of a hexasaccharide repeating unit as shown. The anomeric configurations of the sugar residues were determined by 1H and 13Cn.m.r.spectroscopy on isolated oligomers obtained during the degradative studies and on the intact polysaccharide.
