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

An extracellular acid stable α-amylase from 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). , and for starch hydrolysis were found 1.1 g L, 58.5 μmole min (mg protein), and 73.1 s, respectively. Amylase activity was marginally enhanced by Ca and Fe ions while Cu ions strongly inhibited it. Thermodynamic parameters determined for starch hydrolysis ( , Δ*, Δ*, *, and ) suggests an effective capacity of PV8891 α-amylase towards starch hydrolysis. Thermal stability of PV8891 α-amylase was assessed at different temperatures (30-80 C). Thermodynamic parameters ( , Δ*, Δ*, *) 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.