Extracellular K5 Polysaccharide of Escherichia coli: Production and Characterization

Abstract

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.

Production and purification of an extracellularly produced K4 polysaccharide from Escherichia coli

“…The extracellular K4, obtained from the culture filtrate by tangential flow ultrafiltration (Minitan System -Millipore -PTGC minitan plate 10,000 Mw), was precipitated with cold ethanol (80%). The extracellular K4 was purified by an enzymic deproteinization employing a fungal protease (Manzoni et al, 1993) and was fractionated by ultrafiltration using membranes with different Mw cut offs (300,000; 100,000; 30,000; 10,000 Dalton).…”

“…Its structure consists of equimolar amounts of glucuronic acid, N-acetylgalactosamine and fructose. Unlike other K antigens, such as K5 ( Van et al, 198 1;Manzoni et al, 1993) the K4 polysaccharide is recognized by the host immunological system but the removal of the sugar residue causes the conversion of the K4 antigen into a not immunogenic polysaccharide. Such behaviour could depend on the similarity between the defructosyl-K4 and the biological molecules chondroitin and chondroitin sulphate.…”

Interaction of HIV-1 Tat Protein with Heparin

“…K5 polysaccharide was prepared as described (43). Chondroitin sulfates A and C, dermatan sulfate, and hyaluronic acid were a gift of Dr. M. Del Rosso, University of Florence, Italy.…”

Escherichia coliK5 heparosan fermentation and improvement by genetic engineering

“…10 Heparosan is biosynthesized as a polysaccharide capsule in bacteria including Escherichia coli K5 and Pasteurella multicida. [11][12][13] While the heparosan produced by P. multicida is usually of high molecular weight ~200-300 KDa, 14 the Escherichia coli K5 heparosan is closer to the size of heparin, with an average molecular weight of 10 KDa to 20 KDa. 9,10,15 For this reason, we chose Escherichia coli K5 as our bacterial strain for further study.…”

“…9,10,15 For this reason, we chose Escherichia coli K5 as our bacterial strain for further study. The K5 heparosan polysaccharide, comprises the Escherichia coli capsule and acts as molecular camouflage, rendering reduced immunogenicity 11,12 because of its identical structure to mammalian heparosan, the biosynthetic precursor of heparin and heparan sulfate. The initiation of K5 heparosan synthesis reportedly involves 2-keto-3-deoxyoctulosonic acid.…”