Toxicological studies on a novel phytase expressed from synthetic genes in Aspergillus oryzae

► Phytases allow for use of phytate bound phosphorus. ► We present a Citrobacter braakii phytase produced by Aspergillus oryzae using synthetic genes. ► A high dose did not cause any adverse effect when fed to rats for 13 weeks. ► The phytase did not exhibit irritative, mutagenic or clastogenic potential. ► There are no reasons for safety concerns when using this phytase as a feed additive.