Supplementation effect of ectoine on thermostability of phytase

In this study, we elucidated the supplementation effect of compatible solutes on the thermostability of phytase, designated as PHYA II, which was encoded by the phytase gene phyA I (GeneBank AY013315) from Aspergillus ficuum As3.324 and expressed in Pichia pastoris GS115. When PHYA II in acetate buffer was heated at 90°C for 15 min, more than 80% of the residual activity was retained by adding the cyclic amino acid ectoine, a representative compatible solute. Furthermore, the presence of ectoine led to an increase in the relative hydrolytic rate of sodium phytate by 15.7% with heating at 80°C for 15 min. Among the compatible solutes examined, ectoine was confirmed to be the most efficient thermoprotectant for PHYA II.