Investigation of Phytase Production by a Strain of Aspergillusniger in Submerged Fermentation of Orange peel

Background and Aim : The diet of poultry, fish and pigs is rich in phytic acid. Due to the lack ofthe phytic acid hydrolyzing enzymes in these animal’s digestive system ,they are not able to useits phosphate, so Pi must be added separately to their diet. Phytic acid is an anti-nutrient factor thatforming insoluble complexes with divalent cations, proteins and vitamins. Phytase is an enzymecapable of hydrolyzing phytic acid and releasing organic phosphate. Thus adding phytase to thefeed can increase the nutritional value, leading to no need to use Pi supplements in feed.Methods : In the present study phytase enzyme activity from a strain of Aspergillus niger wasinvestigated for the hydrolysis of agricultural wastes such as Orange peel and wheat bran insubmerged fermentation. Phytase-producing media includes (NH۴ )۲ SO۴, KCl, MgSO۴, FeSO۴and MnSO۴ in ۱۰۰ ml purified water. As a phytic acid source to induce phytase production, wheatbran (A) and orange peel (B)were used in two different media separately(۰.۵ g/۱۰۰ ml). A thirdmedium containing ۰.۵% Sodium phytate (C) was prepared as pure source of phytic acid.Inoculation was done with ۱ ml (۱۰۵ spore/ml) of ۷۲ hours cultured Aspergillus niger plate.Inoculated flasks were incubated at ۳۰ օC at ۱۵۰ rpm. After that the enzyme activity was assayed.Results : B media containing orange peel indicated more enzyme activity(۰.۰۲۵ U/L) than wheatbran(۰.۰۱۵U/L). Moreover, enzyme production in B medium reached the maximum value in ۶۰hours, while this time for wheat bran was longer, ۹۶ h.Conclusion : It is suggested that one reason for the higher enzyme production in B medium, is thelower concentration of free phosphate in orange peel. Researches have shown that citrus peelcontains little mineral phosphorus compared to wheat bran, rice bran, soy bran, etc. Since freephosphate is one of the inhibitors of phytase production by fungies.In research by spire et al., theorange peel was used to produce phytase from Aspergillus niger. In addition, in another study byMittal et al., orange peel was used to induce Klebsiella sp.DB۳ for phytase production.Consideringthat citrus peel utilization in poultry feed has tremendous effects on improving their growth, soadding phytase to the feed, caused the release of Pi and Consequently, by eliminating phosphatesupplements, it reduced environmental pollutions.

کلیدواژه ها:

Aspergillus niger ، Phytase ، Phytic acid