RESUMO
Acute and 90-day subchronic oral toxicity studies were conducted to establish the safety evaluation of xylanases preparations. A potential oxidative stress evaluation was also performed through testing the generation of oxidative radicals, depletion of antioxidants via oxidative modification of lipids, proteins and DNA of organ cells. During the subchronic oral toxicity study, no mortality was observed, obvious treatment-related clinical signs and urinalysis parameters were in normal range. Differences in some hematological parameters, biochemistry, relative organ weight, and histopathology examinations between the treated group and the control group were not judged to be adverse. Our results indicated that the no-observed-adverse-effect level for xylanases was 1,500 TXU/kg/day and the plasma antioxidant assays showed that these xylanases did not produce free-radicals nor oxidative injuries. On the basis of the bacterial reverse mutation assay data, it is concluded that the expressed xylanase in Pichia pastoris do not present any mutagenic potential when tested in relevant genotoxicological assays.