Effects of coating on recovery of <i>Escherichia coli</i>-derived phytase under different steam pelleting conditions

The objective of this study was to evaluate the effect of coating on the recovery rate (<b>RR</b>) of phytase activity during the steam conditioning-pelleting (<b>SCP</b>) process. A split-plot design was employed, with phytases assigned to the main plot and two conditioning temperatures (75 or 85 °C) assigned to the subplot. The whole plot was repeated four times. In Exp. 1, six phytases were analyzed, including an uncoated phytase (<b>NP</b>) NP1 (NP1), two coated phytases (<b>CP</b>) CP1 and CP2 derived from NP1, and three commercial phytases (<b>MP)</b> MP1-MP3. In Exp. 2, coating technology was refined based on the results of Exp. 1, and nine phytases were analyzed, including an NP2, five coated phytases CP3-CP7 derived from NP2, and three commercial phytases MP4-MP6. Phytase activity after the steam-conditioning, pelleting, and cooling process was analyzed, and the RR of phytase activity was calculated for each process. In Exp. 1, significant interactions between phytase and conditioning temperature on the RR of phytase activity were observed (<i>P </i>< 0.05). The RR of CP1 and CP2 did not differ from that of NP1. Commercial phytase MP3 exhibited a lower RR than the other four phytases when conditioned at 75 °C (<i>P </i>< 0.05). Except for MP3, the RR of phytases decreased as the conditioning temperature increased (<i>P </i>< 0.05). In Exp. 2, the RR of phytase decreased as the conditioning temperature increased from 75 to 85 °C (<i>P </i>< 0.05). Compared with NP2, the RR increased, and the loss rate of activity for all five coated phytase (CP3-CP7) decreased after the conditioning process (<i>P </i>< 0.05). Commercial phytase MP4 and MP6 had comparable RR to NP2, while MP5 exhibited a comparable RR to CP3-CP7. In conclusion, the coating technology used in Exp. 1 did not increase the RR of phytase during the pelleting process, whereas the improved coating process employed in Exp. 2 effectively increased the thermostability of phytase.