Apple juice clarification by a purified polygalacturonase from Calonectria pteridis

•Calonectria pteridis secreted a polygalacturonase after submerged cultivation.•Eucalyptus leaf induced the highest polygalacturonase activity.•The highest polygalacturonase activity occurred at pH 4.0 and at 60°C.•The presence of Hg+2 and SDS completely inhibited the polygalacturonase activity.•The polygalacturonase was able to perform apple juice clarification. Polygalacturonases are extensively used in food industries for pectic substances degradation. They are essential for fruit juice clarification due the degradation of insoluble viscous pectinacious compounds. Polygalacturonase production by the fungus Calonectria pteridis was performed on submerged fermentation and, after purification, the enzyme showed a molecular weight of 68kDa. The highest polygalacturonase activity occurred at pH 4.0, and the enzyme preserved more than 70 % of its activity at pH values between 3.6 and 6.0. The optimum temperature was 60°C. The half-life values at 50 and 60°C were 260 and 66min, respectively. The KM value was 0.52mg/mL for the substrate polygalacturonic acid and the presence of Hg+2 and SDS completely inhibited the enzyme activity. The purified polygalacturonase was applied for apple juice clarification and it resulted in a volume and an amount of reducing sugars released increase of 10.65 and 40.93 %, respectively.