Production of Levanbiose by a Levan-degrading Enzyme from<i>Streptomyces exfoliatus</i>F3-2

Abstract

Levan-assimilating microorganisms obtained from soil samples were screened for levan-degrading enzyme production. Among them, the strain F3-2 was found to produce an extracellular levan-degrading enzyme that hydrolyzed levan to a disaccharide identified as levanbiose. The strain F3-2 was identified as Streptomyces exfoliatus F3-2. This levan-degrading enzyme was specifically induced by levan, and the activity was increased to 2.58 units/ml by improvement of the culture conditions. The optimum temperature and pH for the enzyme reaction were 60°C and 5.5, respectively. The crude levan-degrading enzyme was stable within a pH range of 3.0 to 9.0 and at up to 50°C. Using this crude levan-degrading enzyme, 50 mg/ml of levan was converted to levanbiose in amounts of 42 mg/ml.