Background: The review of literature and patents shows that enhancing the polygalacturonase
(PG) production and activity are still required to fulfill the increasing demands.
Methods: A dual optimization process, which involved Plackett-Burman design (PBD), with seven factors,
and response surface methodology, was applied to optimize the production of extracellular PG enzyme
produced by a novel strain of Aspergillus flavus isolated from rotten orange fruit. The fungal PG
was purified and biochemically characterized.
Results: Three variables (harvesting time, pH and orange pomace concentration), that were verified to
be significant by the PBD analysis, were comprehensively optimized via Box-Behnken design. According
to this optimization, the highest PG activity (4073 U/mL) was obtained under pH 7 after 48 h using
40 g/L orange pomace as a substrate, with enhancement in PG activity by 51% compared to the first
PBD optimization step. The specific activity of the purified PG was 1608 U/mg with polygalacturonic
acid and its molecular weight was 55 kDa. The optimum pH was 5 with relative thermal stability (80%)
at 50˚C after 30 min. The PG activity improved in the presence of Cu2+ and Ca2+, while Ba2+, Fe2+ and
Zn2+ greatly inhibited the enzyme activity. The obvious Km and Vmax values were 0.8 mg/mL and
2000 μmol/min, respectively.
Conclusion: This study is a starting point for initial research in the field of optimization and characterization
of A. flavus PG. The statistical optimization of A. flavus PG and its biochemical characterization
clearly revealed that this fungal strain can be a potential producer of PG which has a wide range of industrial