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 75 kDa. 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 1.1 g L(-1), 58.5 μmole min(-1) (mg protein)(-1), and 73.1 s(-1), respectively. Amylase activity was marginally enhanced by Ca(2+) and Fe(2+) ions while Cu(2+) ions strongly inhibited it. Thermodynamic parameters determined for starch hydrolysis (Ε (α), ΔH*, ΔG*, ΔS*, ΔGE-S∗ and ΔGE-T∗ ) suggests an effective capacity of PV8891 α-amylase towards starch hydrolysis. Thermal stability of PV8891 α-amylase was assessed at different temperatures (30-80 (ο)C). Thermodynamic parameters ( E(a)d , 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.