Biotransformation of patulin to hydroascladiol by Lactobacillus plantarum

Growth of Penicillium expansum, an ubiquitous mould found in stored fruit globallyt, was significantly restricted by exposure to 48 h cell-free supernatant of two strains of Lactobacillus plantarum (p < 0.001). In addition, the biotransformation of patulin, a toxic secondary metabolite formed by P. expansum, on exposure to L. plantarum cells and cell-free supernatant highlights the potential of this GRAS microbe as a biocontrol agent. Up to 80% of patulin was biotransformed following a 4 h incubation with 1010 cells ml−1 (37 °C) forming E- and Z-ascladiol. The formation of these products was more pronounced at elevated pH and cell density. Exposure to cell free supernatant or sonicated cells resulted in complete patulin biotransformation with heat treatment inhibiting this effect. The ascladiol isomers were then further transformed over a 4-week cell-free incubation (4 °C) into the novel metabolite hydroascladiol (5-(2-hydroxyethyl)-4-(hydroxymethyl) furan-2(5H)-one) which produced a 2 amu difference across the main tandem mass fragments (113.1, 129.0, 139.0), compared to ascladiol (111.1, 127.0, 137.0). This suggests hydroascladiol could be a better biomarker of initial patulin levels in some food commodities. The in vitro biotransformation data and resistance of L. plantarum to highly elevated concentrations of patulin (≥100 μg ml−1) suggest L. plantarum is a potential candidate for food preservation or remediation strategies and future work with fruit products is proposed.