Fungal endophytes of Vanilla planifolia across Reunion Island: isolation, distribution and biotransformation

Background: The objective of the work was to characterize fungal endophytes from aerial parts of Vanilla planifolia. Also, to establish their biotransformation abilities of flavor-related metabolites. This was done in order to find a potential role of endophytes on vanilla flavors. Results: Twenty three MOTUs were obtained, representing 6 fungal classes. Fungi from green pods were cultured on mature green pod based media for 30 days followed by H-1 NMR and HPLC-DAD analysis. All fungi from pods consumed metabolized vanilla flavor phenolics. Though Fusarium proliferatum was recovered more often (37.6 % of the isolates), it is Pestalotiopsis microspora (3.0 %) that increased the absolute amounts (quantified by H-1 NMR in mu mol/g DW green pods) of vanillin (37.0 x 10(-3)), vanillyl alcohol (100.0 x 10(-3)), vanillic acid (9.2 x 10(-3)) and p- hydroxybenzoic acid (87.9 x 10(-3)) by significant amounts. Conclusions: All plants studied contained endophytic fungi and the isolation of the endophytes was conducted from plant organs at nine sites in Reunion Island including under shade house and undergrowth conditions. Endophytic variation occured between cultivation practices and the type of organ. Given the physical proximity of fungi inside pods, endophytic biotransformation may contribute to the complexity of vanilla flavors.