Identification and characterization of thermostable endo‐polygalacturonase II B from Aspergillus luchuensis. Issue 3 (5th January 2020) - Tan, Haidong
Abstract: Endo‐polygalacturonase II B (PgaB) from Aspergillus luchuensis was orthologous to endo‐polygalacturonase from Aspergillus niger with mutant sites Thr42Ser and Glu52Ala. Mature pga B gene was cloned from the genomic DNA of A. luchuensis and secreted expressed with over 90% purity in Pichia Pastoris and reached 1.0 g/L after 144 hr culture. The recombinant PgaB was further purified by Ni‐NTA chromatography. Using polygalacturonic acid (PGA) as substrate, the optimal condition for PgaB activity was 40°C and pH 4.5, respectively. Km and Vmax of PgaB were 0.19 mmol/l and 103.58 μmol min −1 mg −1, respectively. The relative activity of PgaB remained more than 60% and 40% of maximum activity at 50 and 60°C for 7 hr. PgaB increased the light transmittance by 85% and showed high efficiency in juice clarification. The main product was galacturonic acid oligosaccharides with degrees of polymers (DP) 1–3. The PgaB is a potential pectinolytic enzyme in food industries. Practical applications: Endo‐polygalacturonase II B (PgaB) was identified from Aspergillus luchuensis, a filamentous fungus widely used in food and beverage fermentation in East Asia. PgaB still kept its most activity at 60°C for 7 hr. Polygalacturonic acid (PGA) can be digested effectively by the PgaB and the main products are galacturonic acid oligosaccharides with degrees of polymers (DP) 1–3. PgaB shows high efficiency in juice clarification. The PgaB is a potential pectinolytic enzyme for the applications in food industries.