Patulin Biodegradation by <i>Rhodosporidiobolus ruineniae</i> and <i>Meyerozyma guilliermondii</i> Isolated From Fruits

Patulin (PAT) is a toxic secondary metabolite produced by certain species of Penicillium and Aspergillus on pome fruits. In this study, we isolated Rhodosporidiobolus ruineniae (R. ruineniae) and Meyerozyma guilliermondii (M. guilliermondii) from a peach and an apple as candidates for PAT degradation, respectively, and investigated the effects of three key parameters (incubation time and temperature, and initial PAT concentration) on PAT removal rates, and the mechanism involved in PAT degradation by the yeast strains. The PAT degradation rate by the yeast strains was dependent on the three key parameters. Both yeast strains were able to degrade 1 μg mL^-1 of PAT to below the regulatory limit (50 µg L^-1) at 60 h when they were incubated at 35°C. The PAT removal by the yeast strains was not due to either binding onto yeast cell walls or degradation by extracellular fractions of the yeast culture among three yeast cell fractions (cell walls, extracellular, or intracellular fractions). The use of spheroplast or intracellular enzymes confirmed that PAT degradation occurred inside the yeast cells. Moreover, the PAT degradation ability was inducible in M. guilliermondii. LC/MS/MS analysis showed that (E)-ascladiol is the sole PAT biodegradation product from both yeast strains. Our data demonstrated that both yeast strains were able to degrade PAT and produce (E)-ascladiol, a less toxic product. These results could be exploited for practical applications to efficiently control PAT on fruits such as apples and peaches.