Characterization of intact Penicillium spores by matrix-assisted laser desorption/ionization mass spectrometry

The fungal spores of Penicillium expansum, P. chrysogenum, P. citrinum, P. digitatum, P. italicum, and P. pinophilum were characterized by using matrix-assisted laser desorption/ionization with time-of-flight mass spectrometry (MALDI-TOFMS). These fungal spores are frequently found in grain and fruit. The mass spectra of these six species were directly obtained from the intact spores without any pretreatment. The results obtained indicate that 2,5-dihydroxybenzoic acid and sinapinic acid are suitable matrices for the analysis of Penicillium spores. Characteristic ions representing the different species were obtained with sufficiently high reproducibility that these ions can be employed to identify the different fungal species. On the basis of these characteristic ions obtained from these authentic Penicillium spores, the approach was applied to characterize the fungal species contaminating the surfaces of fruit. It was demonstrated that the fungal spores directly scratched from the surfaces of fruit contaminated by unknown fungi can be rapidly identified using MALDI-TOFMS analysis without any tedious pretreatment.