Abstract

A marine exopolysaccharide (EPS) producing bacterium was isolated from a sponge sample at about 16 m depth in red sea (Huraghada, Egypt). Phenotypic characterization demonstrated that, the bacterium is a gram negative rod motile by means of single polar flagellum, showing wide range of carbohydrate utilization. Phylogenetic analysis based on 16S Ribosomal deoxyribonucleic acid (rDNA) sequence revealed 99% homology withPseudoalteromonas sp., accordingly the name Pseudoalteromonas sp. AM was proposed. Maximum EPS productivity was achieved after 7 days at pH 7, agitation of 150 rpm in a fermentation medium containing glucose, meat extract and 3% NaCl. The partially purified EPS had emulsifying activity about 78% and retained its stability for about 13 days. Extended emulsion stability for up to 22 days was shown by increasing the concentration of EPS from 0.01 to 0.1% w/v. The EPS elicited a marked antiviral activity against herpes simplex (HSV-I) and showed lysis of plasma clots comparable to pentosan sulphuric polyester as a standard. Preliminary characterization of EPS by complete acid hydrolysis then analysis on paper chromatography revealed the presence of a single brown spot equidistant with authentic glucose indicating that EPS is mainly composed of glucose units. Further investigations will be carried out to realize the full structure and chemical composition of the produced EPS and other possible biotechnological potential.

Key words: Exopolysaccharide, Pseudoalteromonas sp., emulsifying activity, antiviral activity, fibrinolytic activity.

Abbreviation

Abbreviations: rDNA, Ribosomal deoxyribonucleic acid; DNA, deoxyribonucleic acid;PCR, polymerase chain reaction; NCBI, national center for biotechnology information;EPS, exopolysaccharide; BLAST, basic local alignment search tool; rRNA, ribosomalribonucleic acid; CDV, challenge dose virus; HSV-I, herpes simplex; MEM, minimal essential medium.