Isolation and characterization of â-amylase from Penicillium nigricans

Author(s): Uday M.Muddapur, Rajani S.Bennur, S.M.Veena, Francois N.Niyonzima, Sunil S.More

A â-amylase-producing fungus was isolated from forest soil by culture plate method with starch as the sole source of carbon and identified as Penicillium nigricans. The failure to develop a clear zone around the fungal colony after staining with iodine in situ indicated the absence of á- amylase in the isolate. The -amylolytic nature was further confirmed by the presence of maltose as the major end product of starch breakdown following thin layer chromatography. The isolate showedmaximumenzyme activity on the 23rd day of cultivation. The partly purified enzyme showed highest activity at 60° and pH 5.0. About 70% of the enzyme activity was retained within the range pH 3.5-7.0. The calcium ion had an enhancing effect whereas Na+, Mn2+, Mg2+, Cu2+, Fe2+ and Ag+ ions moderately inhibited the-amylase activity. The â-mercaptoethanol had an inhibitory effect on the enzyme. The enzyme was completely inhibited by ethylenediaminetetraacetic acid (EDTA) suggesting the isolated enzyme to be ametalloenzyme. The enzyme showed highest activity towards starch followed by amylose and did not show any cross specificity towards cellulose. Absence of substrate cross specificity and ability to hydrolyse waste starches made the enzyme candidate for industrial applications.

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