Flavobacterium johnsoniae is capable of secreting enzymes which can efficiently hydrolyze yeast cell wall. Preliminary analysis revealed the presence of glucanase, chintinase and protease activities in its culture supernatant. A laminarinase was purified from the extracellular components of F. johnsoniae through several isolation steps including ion exchange, hydrophobic interaction and gel exclusion chromatography. The molecular weight of the purified laminarinase is about 35 kD. The optimum temperature and pH of its catalyzed hydrolysis are 50 °C and 5.0, respectively. Laminarin and laminari-oligosaccharide were hydrolyzed by this laminarinase in an endoglucanase mode with laminaritriose as the main product.