Polygalacturonase from Aspergillus japonicus (PGAj): Enzyme production using low-cost carbon source, biochemical properties and application in clarification of fruit juices

Abstract

Aspergillus japonicus polygalacturonase (PGAj) was produced using passion fruit peel, a residue from the agricultural and juice industries, as a low-cost carbon source. The biochemical properties of the enzyme and its application in the clarification of fruit juices were investigated. The maximum PGAj production was obtained using solid state fermentation (SSF) in 48 h (227.75 ± 13.1 U). PGAj was purified in two chromatography steps with a specific activity of 7.9 U/mg protein, 2.9 -fold purification, and 81% final yield, exhibiting a molecular weight about 40 kDa. The optimal pH and temperature for PGAj activity were pH 4.0 and 55 °C, respectively. Moreover, the PGAj enzyme retained up to 90% of its initial activity for 4 h at pH 4.0, 5.0 and 6.0. The enzyme maintained 83% residual activity after 20 min at 50 °C. PGAj best preferred citrus pectin (8.45 ± 1.6 U/mg protein) as substrate. The best results for juice clarification using 3 U/mL PGAj were obtained with the pulp of Palmer and Tommy mango varieties, white guava, banana, and apple, with increases of 65%, 41%, 40%, 11%, and 9.4% in transmittance values, respectively, compared to the control. This was superior to that obtained using commercial pectinase for some of the pulps, as 49% and 21% for Palmer and Tommy mango pulps, respectively. Thus, PGAj may be suitable for application as a clarifying agent in the fruit juice industry. • Polygalacturonase (PGAj) was produced using a low-cost carbon source (passion fruit peel). • PGAj was obtained in 48 h solid state fermentation (SSF). • Better clarification of mango juice achieved with PGAj than with commercial pectinase.