Statistical optimization of culture conditions for endopolygalacturonase production by Aspergillus niger using solid orange waste

Scanning electron microscopy analysis of Aspergillus niger growth on orange residue showed that the microorganism grows well on the medium by synthesizing the pectolytic enzymes. A two-level full factorial design was used for screening the most important factors for the production of endopectinase (endo PG) from dry orange waste by Aspergillus niger among dry orange waste pellet size, concentration of ammonium sulphate, concentration of glucose and moisture content. Three significant factors influencing endo PG production were identified: concentration of ammonium sulphate, moisture content and glucose concentration. The particle size of the dry orange waste may not affect the process bat its interaction with moisture has significant effect. The effects of the significant factors were further investigated using a design of rotation-regressio-northogonal combination. The optimised medium according to response surface methodology (RSM) analysis contained 1.98% ammonium sulphate 1.83% glucose and 54,63 of distilled water. Under the optimised conditions, the model predicted 25,57 U/ml in crude extract, whereas validation experiments produced an endo PG enzymatic activity of 32.41 U/ml. This study is innovatively a fermentation medium to use inexpensive agro-industrial wastes to produce a high yield of pectinase.