Biochemical characterization of the recombinant polygalacturonase PGB and the activity analysis of its enzymatic hydrolysis product

To analyze the enzymatic properties of recombinant polygalacturonase PGB and to study the compositions and biological activities of pectin hydrolysate prepared by PGB.Polygalacturonase was prepared by shake flask fermentation and its enzymatic properties were investigated.Pectin was hydrolyzed by PGB under optimum conditions, followed by investigation of its compositions, and antioxidant and antibacterial activities. At the shake flask fermentation level, the activity of PGB reached10790 U/m L.Its optimum temperature and p H was 55 ℃ and 5.0, respectively.And it was quite stable at 40 ℃ or p H4.0 ⁶.0.Mg²⁺and Cu²⁺enhanced its activity, while K⁺, Ca²+, Zn²⁺, Mn²⁺, Co²⁺, Fe3 +and Fe²⁺had different inhibitory effects on its activity.The Kmand Vmaxof PGB toward low-ester pectin was determined to be 0.756 mg/m L and 9.225 mg/ ( m L·min) . After hydrolyzed by PGB, pectin hydrolysate was identified as galacturonic acid and oligogalacturonic acid with a polymerization degree of 2 to 4 by high performance anion exchange chromatography-pulsed amperometric detector ( HPAEC-PAD) . This oligomer significantly inhibited the growth of Staphylococcus aureus, and its minimum inhibitory concentration and antioxidant activity was 0.64 mg/m L and 6.125 U/m L, respectively.