Determinazione della termoresistenza e caratterizzazione molecolare di ceppi di Paecilomyces spp. isolati da prodotti acidi pastorizzati.

Recent studies on Paecilomyces variotii, a fungal species that has long been thought to be non heat-resistant, showed that its increasingly frequent isolation from pasteurized products containing fruit derivatives is due to its ability to sexually reproduce by forming heat-resistant ascospores, in case it crosses with strains of the opposite sex mating type. The aim of the present work was thus: (i) to characterize the mating type of the P. variotii strains from the SS ICA collection through the use of molecular and cultivation techniques, (ii) to carry out heat resistance tests on the ascospore suspensions obtained in the crossing of the strains proven fertile by identifying the time / temperature combinations required for activation and subsequent inactivation of ascospores and (iii) to determine whether heat treatments can somehow select the growth of a mating type over the other. The results obtained showed the extreme heat resistance of this fungal species: at 90 ° C maximum activation of ascospores was reached, for whose subsequent inactivation were needed longer times (75 minutes) than those used for other heat-resistant species.