Optimized production of Aspergillus aculeatus URM4953 polygalacturonases for pectin hydrolysis in hog plum (Spondias mombin L.) juice

Production of total polygalacturonase (PG) and endo-polygalacturonases (endo-PG) from Aspergillus aculeatus URM4953 was optimized in submerged fermentation using passion fruit peel as substrate for pectin hydrolysis in hog plum juice. The highest activities of PG (2.92 ± 0.12 U/mL) and endo-PG (6.51 ± 0.04 U/mL) were obtained at 30 °C, pH 4.56 and 130 rpm, using 3.0% substrate and 0.1% yeast extract after 96 h in 250-mL Erlenmeyer flasks. Under these optimized conditions, maximum specific growth rate of the microorganism was 0.06 h⁻¹, saturation constant 9.9 mg/mL, yield of biomass on consumed substrate 1.44 g/g, yields of PG and endo-PG on consumed substrate 0.33 and 0.81 U/mg, and yields of PG and endo-PG on biomass 0.45 and 0.95 U/mg, respectively. Endo-PG, which is responsible for reduction of fruit juice viscosity, displayed an optimum temperature of 60 °C and two optimal pH values (5.0 and 7.0). A novel zymography method showed PG activity in correspondence to a protein band of 31.7 kDa. The enzyme mixture was used for pectin hydrolysis in hog plum juice, which occurred optimally at 40 °C, achieving a juice yield of 35.3% and reducing fruit viscosity by 96.8% within 88 min. A. aculeatus polygalacturonases have been demonstrated to have great industrial potential for pectin hydrolysis in fruit juices.