African Journal of Biotechnology Vol. 6 (19), pp. 2280-2286, 4 October 2007   

ISSN 1684–5315 © 2007 Academic Journals        

Full Length Research Paper

Inhibition of phage infection in capsule-producing Streptococcus thermophilus using   concanavalin A, lysozyme and saccharides

Rowaida Khalil¹*, Joseph F. Frank², Ashraf N. Hassan³, and Sanaa H. Omar¹

¹Botany Department, Faculty of Science, Alexandria University, Alexandria, Egypt.

²Department of Food Science and Technology, University of Georgia, Athens, GA 30602 USA.

³Dairy Science Department, South Dakota State University, Brookings, SD 57007, USA.

*Corresponding author. E-mail: rowaida_georgia1@hotmail.com. Tel: 002-3921595. Mobile. 002 0123772803. Fax: 002-3911794.

Accepted 16 July, 2007

Lactic cultures that produce capsular polysaccharides are widely used in the dairy industry. However, little information is available on their phage-cell interactions.  Concanavalin A (Con A), lysozyme, and saccharides were investigated for their ability to modify phage-cell interactions in such a manner as to inhibit phage infection. The ability of phage to infect cells was determined by measuring acid production in Elliker broth. Acid production by capsule-producing Streptococcus thermophilus was inhibited less by bacteriophage when cells were pretreated with Con. A than was acid production by a capsule-free variant. The presence of 0.5 mg/ml lysozyme in Elliker broth significantly reduced phage infection. However, there was no increased effect when lysozyme and Con A were combined in the growth medium. The addition of 5 g/L of glucosamine to Elliker broth also inhibited phage infection. The results of this study indicate that it is possible to reduce phage infection of capsule-forming S. thermophilus by blocking or modifying phage adsorption sites.

Key words: Capsular polysaccharides, Concanavalin A, bacteriophage adsorption, adsorption sites, phage inhibition.