Evaluation of production and characterization of polygalacturonase by Aspergillus niger ATCC 9642

The aim of our study was to evaluate polygalacturonase (PG) production and characterization by Aspergillus niger ATCC 9642. The maximum PG activity (51.82 U/mL) was obtained using pectin, l-asparagine, and, iron sulphate concentrations of 32 g/L, 2 g/L, 0.06 g/L and 1.0 g/L, respectively; 180 rpm of stirring rate, 25 °C and an initial pH of 4.0. The kinetic study showed that the highest enzyme activity was achieved at 27 h of fermentation. The evaluation of the optimum pH and temperature permitted us to observe that highest PG activities were achieved at 37 °C and pH of 5.5. The enzymatic extract presented higher stability at 55 °C and pH of 5.0. The results showed that at low temperatures the enzyme extract kept the initial activity until 40 days of storage. The experimental design methodology permitted us to optimize the PG activity and an important aspect of this study is the characterization of the PG in terms of optimum temperature and pH using experimental design technique and also, the characterization of enzyme stability at low temperature. Such studies are very scarce in the literature and should be helpful to understand the true potentialities of pectinases in its industrial applications.

Research highlights▶The maximum polygalacturunase activity was 51.82 U/mL. ▶ Interesting results in terms of PG activity when compared to the current literature. ▶ The optimum pH and temperature were achieved at 37 °C and pH of 5.5. ▶ PG activity was kept for longer times at 55 °C and pH of 5.0. ▶ At low temperatures, the enzyme kept the initial activity until 40 days of storage.