Journal of Applied Microbiology, Vol.109, No.2, 408-414, 2010
Use of the Weibull model to describe inactivation of dry-harvested conidia of different Penicillium species by ethanol vapours
Aims: This study aimed at modelling the effect of ethanol vapours, in the range 0 center dot 7-7 center dot 5 kPa, on the inactivation of dry-harvested conidia of Penicillium chrysogenum, Penicillium digitatum and Penicillium italicum. Methods and Results: Survival curves were modelled by a Weibull model: log (N/N-0) = -1/2 center dot 303 (t/alpha)beta. The shape parameter beta was different from one in all cases, indicating that the classical first-order kinetics approach is the exception rather than the rule. Survival curves exhibited upward concavity (beta < 1) with the notable exception of P. chrysogenum at ethanol vapour pressures 0 center dot 7 and 1 center dot 5 kPa. The scale parameter alpha (h) varied greatly depending on the ethanol vapour pressure and on the species. Conclusions: For safety reasons, it is recommended not to exceed an ethanol vapour pressure of 3 center dot 3 kPa. At 2 center dot 8 kPa, more than 4 log(10) reductions in viable conidia were achieved for all the species after 24-h exposure. Significance and Impact of the Study: Ethanol has GRAS status in the USA and represents an interesting alternative to fungicides. The effectiveness of ethanol vapours to inactivate dry-harvested conidia of some Penicillium was demonstrated in this study.
Keywords:conidia;ethanol;fungi;inactivation;Penicillium chrysogenum;Penicillium digitatum;Penicillium italicum;predictive mycology