Microparticle-enhanced polygalacturonase production by wild type Aspergillus sojae

Polygalacturonases (PGs), an important industrial enzyme group classified under depolymerases, catalyze the hydrolytic cleavage of the polygalacturonic acid chain through the introduction of water across the oxygen bridge. In order to produce and increase the concentration of this enzyme group in fermentation processes, a new approach called microparticle cultivation, a promising and remarkable method, has been used. The aim of this study was to increase the PG activity of Aspergillus sojae using aluminum oxide (Al₂O₃) as microparticles in shake flask fermentation medium. Results indicated that the highest PG activity of 34.55 ± 0.5 U/ml was achieved with the addition of 20 g/L of Al₂O₃ while the lowest activity of 15.20 ± 0.2 U/mL was obtained in the presence of 0.1 g/L of Al₂O₃. In fermentation without microparticles as control, the activity was 15.64 ± 3.3 U/mL. Results showed that the maximum PG activity was 2.2-fold higher than control. Additionally, smaller pellets formed with the addition of Al₂O₃ where the lowest pellet diameter was 955.1 µm when 10 g/L of the microparticle was used. Also, it was noticed that biomass concentration gradually increased with increasing microparticle concentration in the fermentation media. Consequently, the PG activity was significantly increased in microparticle-enhanced shake flask fermentation. In fact, these promising preliminary data can be of significance to improve the enzyme activity in large-scale bioreactors.