Application of Doehlert design to determine the combined effects of temperature, water activity and pH on conidial germination of Penicillium chrysogenum

Aims: The influence of temperature, water activity and pH on the time necessary for germination of 90% of Penicillium chrysogenum conidia inoculated (T-90) was determined. Methods and Results: A new experimental device was developed for easy monitoring of the germination process. Experiments were carried out according to a Doehlert matrix at 11-31 degreesC, 0.86-0.98 water activity (a(w)) and pH 3.5-6.5. In these conditions, a second order polynomial relationship between T-90 and the environmental factors was established for the different, humectants used throughout this study (e.g. glycerol and sorbitol), with regression coefficients close to 0.97. Conclusions: For both humectants, the major effect of temperature and water activity on T-90 was highlighted, whereas the effect of pH on T-90. in these experimental conditions was not significant. The combined effect of temperature and water activity on T-90 was also demonstrated. Significance and Impact of the Study: Both the experimental set-up and the Doehlert matrix were well suited to determine the influence of environmental factors on mould germination.