Streptavidin assay by means of biotinylated actinophages

Using D-biotinyl-N-hydroxysuccinimide ester, biotin was covalently attached to actinophage SLE 111. The chemically modified actinophage preparation (SLE 111-BIO) was prevented from forming plaques by biotin-binding proteins, such as streptavidin and avidin. The avidin concentration at 50% inactivation of biotinylated actinophages was 0.5 micrograms/ml. The streptavidin assay was useful as pre-selection method during the screening and improvement work with streptavidin-producing microorganisms.