Production of Extracellular Recombinant Phytase in Yeast and Its Application in Animal Feed as Enzyme Supplement

Phytase is a crucial enzyme widely employed in animal nutrition and agriculture for hydrolyzing phytic acid (phytate), the primary storage form of phosphorus in plant tissues, thereby releasing digestible inorganic phosphate. However, its commercial application is often constrained by the thermal instability of enzyme, particularly under the elevated temperatures used in industrial feed processing. To address this limitation, the present study aimed to develop a robust and scalable yeast-based expression system capable of producing a thermostable form of phytase. A novel expression plasmid, pESC-TRP6HisHA, was constructed, featuring galactose-inducible bidirectional promoters, a 6×His-HA epitope tag for easy detection, and a secretion signal to facilitate extracellular expression. The PhyA gene from Aspergillus niger, encoding phytase, was cloned into this vector, resulting in the construct pESC-TRPHSignalSeqPhyA, which was subsequently transformed into Saccharomyces cerevisiae. Under galactose induction and phytin-supplemented media, the recombinant yeast successfully expressed and secreted active phytase, as evidenced by clear halo zones on phytin-containing agar plates. Biochemical assays demonstrated that the recombinant phytase exhibited significantly enhanced thermostability compared to the wild-type enzyme, retaining greater enzymatic activity after incubation at 30°C, 40°C, and 50°C for three hours. This improvement was supported by an aliphatic index of 83.2, suggesting moderate thermal resilience. The expression system offers a dual benefit of both secretion and potential surface display, enhancing flexibility for downstream applications. This study establishes a simple, efficient, and scalable platform for the production of thermostable phytase using genetically engineered S. cerevisiae. The system holds substantial promise for industrial applications, especially in animal feed manufacturing, where enzyme stability at high temperatures is critical. Future work will focus on optimizing yield, evaluating long-term stability, and conducting feed trials to validate its performance under commercial conditions.