Alternariol Detoxification by Rhodotorula taiwanensis P1 Isolated from a Pear and Its Mechanism

Alternariol (AOH) is a mycotoxin produced mainly by Alternaria alternata on fruits including tomatoes and strawberries as well as cereal grains including wheat and soybeans. In this study, we isolated Rhodotorula taiwanensis (R. taiwanensis) P1 from a pear and investigated the effects of incubation time and temperature on AOH reduction rates and the mechanism involved in AOH detoxification by the yeast strain. The yeast strain showed a 76.10% AOH reduction rate from the initial level (1 μg/mL) at 30 °C after 48 h of incubation. The yeast cell-free filtrate from the yeast culture did not increase the AOH reduction rate relative to the control without cell-free filtrate after 48 h. In addition, the AOH reduction rate by heat-inactivated yeast cells (74.57%) was similar to that by viable yeast cells (76.33%). The AOH detoxification test using the yeast cell wall fraction showed that AOH binds to its cell walls and that approximately 1/3 of the AOH bound onto the cell walls was extracted from them. These data strongly suggest that the AOH detoxification by the yeast strain was not due to degradation by either intracellular enzymes or extracellular enzymes of the yeast culture but was due to binding to yeast cell walls. The use of spheroplasts, in which cell walls are deficient, confirmed that AOH detoxification occurred by binding onto the cell walls of R. taiwanensis. Our data demonstrated that R. taiwanensis P1 was able to remove AOH by adsorption onto its cell walls. These results could help in the development of potential strategies to effectively mitigate AOH contamination of food.