Extracellular K5 Polysaccharide of Escherichia coli: Production and Characterization

The extracellular form of the K5 polysaccharide was produced, purified and characterized from a strain of Escherichia coli,the maximum fermentation yield (320 mg/L) was obtained after 15 h. The polysaccharide, recovered by precipitation with cold ethanol (80%), was purified through a pro cess employing an enzymic deproteination step using fungal protease. Charac terization by TLC and GC chromatography revealed that the K5 was mainly composed of glucuronic acid and N-acetyl-glucosamine. The 13C-NMR spectrum showed the product's structure to be the same as that of the K5 capsular polysaccharide described in the literature.