Safety assessment of a novel thermostable phytase

A novel 6-phytase (Phytase TSP, trade name OptiPhos® PLUS) with improved thermostability has been developed for use in animal feed. The safety of the new phytase was evaluated by testing for genotoxicity and subchronic toxicity. In in vitro and in vivo genotoxicity assays Phytase TSP concentrate was not mutagenic and did not induce biologically or statistically significant increases in the frequency of micronucleated polychromatic erythrocytes. In a subchronic toxicity study, male and female rats administered 100, 500 or 1000 mg/kg body weight/day of Phytase TSP concentrate via oral gavage for 90 days had no mortalities, and no treatment-related effects on body weight, food consumption, clinical observations or ophthalmology. Furthermore, there were no changes in haematology, clinical chemistry, urinalysis, gross pathology, organ weights or histopathology that could be attributed to the test article. Several endpoints exhibited statistically significant effects, but none was dose-related or considered to be of toxicological relevance. Based on these results, Phytase TSP concentrate (OptiPhos® PLUS) was not genotoxic and the No Observed Adverse Effect Level (NOAEL) for male and female rats was 1000 mg/kg body weight/day.