Studies On Isolation,Purification And Enzymological Characteristics Of Pectinase From Aspergillus Niger

Pectinase is a collective call for any enzyme which breaks down pectic substance. Primarily, it contains components such as polygalacturonase.pectinesterase and pectin lyase.Each component differs from others in the mechanism of reaction and its characteristics.Aspergillus niger was the major genera of microorganisms producing pectinase in industry.In order to exploit the capacity of Aspergillus niger in producing the enzyme and know much about its enzymological characteristics, it is of more significant to carry out this paper.In this study, the production conditions of three components of pectinase from Aspergillus niger SL2-111 were investigated. The two main components of pectinase namely PG and PE were isolated, purified and characterized.Major results were as follows:(1)The medium containing seed capsule could improve pectinase production in solid-state fermentation.The optimal medium and culture condition for PG, PE and PL production were different.Under the best condition.the activity of PG, PE and PL per gram leaven were 2695U/g, 32975U/g and 0.177U/g respectively.(2)Two components of pectinase namely PG and PE were purified from Aspergillus niger pectinase preparation by ammonium sulfate fractionation, DEAE Sepharose Fast Flow ion exchange chromatography, Sephacryl S-200 gel filtration. Both PG and PE were homogeneous on polyacrylamide gel electrophoresis.(3)The molecular mass of PE was 48.8kDa,the optimal pH and temperature was 5.8 and 60℃ respectively.PE was stable in the range of pH from 4.2 to 7.0. After 60 min incubation at 50℃,this component of pectinase remained 40 percent of the total activity.(4)The molecular mass of PG was 71.5kDa, the optimal pH and temperature was 3.0 and 65℃ respectively.PG was stable in the range of pH from 2.6 to 5.4. After 60 min incubation at 50℃,this component of pectinase remained 41 percent of the total activity.Metal ions such as Ca2+, Li+, Cu2+, Mg2+,K+ could stimulate PG activity,especially the stimulation of Ca2+ was more remarkable than others. Mn2+and Ag+ were inhibitors of PG activity. PG had a higher content of acidic amino acid such as Asp, Thr, Ser, Glu, Val.In contrast, content of alkaline amino acid such as His was more lower than the acidic ones.