Evaluating the nutritional impact of co-expressed phytase genes from Escherichia coli and Aspergillus niger in Pichia pastoris on broiler chickens.

Two phytase genes originating from Escherichia coli (6-phytase) and Aspergillus niger (3-phytase) (appA and phyA) were co-expressed in Pichia pastoris as the expression host. In vivo and in vitro tests were employed to assess the biological properties of the recombinant phytase. The recombinant protein had a phytase activity equal to 160.97 U/ml and was tested in the feed of 180 broilers to measure Crude Protein, Dry Matter, Fat, Phosphorus, Calcium, Iron, Magnesium, Zinc and p-phytate digestibility. The experimental chickens were subjected to six dietary treatments in six replicates (5 birds per replicate). The treatments included one control group (basal diet), and three feed treatments with 500, 1000, and 1500 FTU phyA + appA. The basal diet contained 500 FTU/kg Hostazym® P, and the basal diet contained native Pichia pastoris. Total tract apparent disappearance of phytate-P and nutrient retention were assessed at 19-21 days of age. Broilers fed with phytases had greater retention of P, Ca, Mg, Fe and p-phytate, and the digestibility of CP and DM (P < 0.05) was greater than the control group. Fat digestibility and Zn retention were not significantly different. As a result, the recombinant phytase used in this study could be used as a feed supplement in poultry farming to enhance mineral digestibility.