Production, optimization and characterization of extracellular invertase by an actinomycete strain

Streptomyces sp. ALKC8 produced high levels of extra-cellular invertase (350 Ul) after incubation for 24 h at pH 5.0, temperature 37°C in the presence of sucrose (3%). The optimum temperature and pH for enzyme activity were 60°C and 5.0 respectively. All metal ions except Na, Hg and Ca were well tolerated and did not adversely affect invertase activity. However, SDS inhibited the enzyme activity. The effect of thermal stabilizers on invertase activity was studied. Consequently, polyethylene glycol and mannitol were shown to have a protective effect on enzyme activity. Maximum invertase activity (581 Ul) was produced by cells grown in the medium containing sucrose (2% w/v) and yeast extract in combination with NaNO3, which was about twofold higher than the production in basal medium.