Catalytic and thermodynamic properties of an acidic α-amylase produced by the fungus Paecilomyces variotii ATHUM 8891.

Abstract

An extracellular acid stable α-amylase from Paecilomyces variotii ATHUM 8891 (PV8891 α-amylase) was purified to homogeneity applying ammonium sulfate fractionation, ion exchange and gel filtration chromatography and exhibited a reduced molecular weight of 75kDa. The purified enzyme was optimally active at pH 5.0 and 60°C and stable in acidic pH (3.0-6.0). K m, v max and k cat for starch hydrolysis were found 1.1g L-1, 58.5 μmole min-1 (mg protein)-1, and 73.1s-1, respectively. Amylase activity was marginally enhanced by Ca2+ and Fe2+ ions while Cu2+ ions strongly inhibited it. Thermodynamic parameters determined for starch hydrolysis (Ε α, ΔH*, ΔG*, ΔS*, and ) suggests an effective capacity of PV8891 α-amylase towards starch hydrolysis. Thermal stability of PV8891 α-amylase was assessed at different temperatures (30-80οC). Thermodynamic parameters ( , ΔH*, ΔG*, ΔS*) as well as the integral activity of a continuous system for starch hydrolysis by the PV8891 α-amylase revealed satisfactory thermostability up to 60°C. The acidic nature and its satisfactory performance at temperatures lower than the industrially used amylases may represent potential applications of PV8891 α-amylase in starch processing industry.