A Novel Endo-Polygalacturonase from Penicillium oxalicum: Gene Cloning, Heterologous Expression and Its Use in Acidic Fruit Juice Extraction

An endo-polygalacturonase (endo-PGase) exhibiting excellent performance during acidic fruit juice production would be highly attractive to the fruit juice industry. However, candidate endo-PGases for this purpose have rarely been reported. In this study, we expressed a gene from Penicillium oxalicum in Pichia pastoris. The recombinant enzyme PoxaEnPG28C had an optimal enzyme activity at pH 4.5 and 45??C and was stable at pH 3.0???6.5 and < 45??C. The enzyme had a specific activity of 4,377.65 ?? 55.37 U/mg towards polygalacturonic acid, and the Km and Vmax values of PoxaEnPG28C were calculated as 1.64 g/l and 6127.45 U/mg, respectively. PoxaEnPG28C increased the light transmittance of orange, lemon, strawberry and hawthorn juice by 13.9 ?? 0.3%, 29.4 ?? 3.8%, 95.7 ?? 10.2% and 79.8 ?? 1.7%, respectively; it reduced the viscosity of the same juices by 25.7 ?? 1.6%, 52.0 ?? 4.5%, 48.2 ?? 0.7% and 80.5 ?? 2.3%, respectively, and it increased the yield of the juices by 24.5 ?? 0.7%, 12.7 ?? 2.2%, 48.5 ?? 4.2% and 104.5 ?? 6.4%, respectively. Thus, PoxaEnPG28C could be considered an excellent candidate enzyme for acidic fruit juice production. Remarkably, fruit juice production using hawthorn as an material was reported for the first time.