Purpose: The aim of this work is to study and model the impact of dioxygen concentrations on Pseudomonas fluorescens growth and assess whether residual oxygen concentration is sufficient for the development of aerobic microflora.
Methods: Pseudomonas fluorescens was cultured in BHI agar medium supplemented with 0.2% of glucose, 0.3% of yeast extract and rezazurin. All petri-dishes were prepared in advance, stored in an hypoxia laminar flow hood, inoculated and then stored at 25°C. To determine kinetics, 15 samplings were performed for given condition of O2 enriched atmosphere. For each sampling time, agar medium was collected, diluted and plated to determinate bacterial population. Growth rate was estimated by fitting logistic primary model using delay and rupture.
Results: Growth rates were acquired for 9 concentrations of dioxygen between 0.1% to 6% for Pseudomonas fluorescens. With only 0.1% of dioxygen, the growth of pseudomonas is possible and an increase of the concentration of dioxygen resulted in an increase of growth rate of up to 5% O2, value from which growth rate is stabilizing. Based on Zwietering gamma concept and Rosso cardinal model, this study integrates a new factor in predictive modeling which is the concentration of dioxygen.
Significance: This experimental protocol allowed performing data under statics residual dioxygen concentrations between 0.1% to 6% during several days. Taking into account the impact of residual dioxygen concentrations on bacterial growth in agar based media, will further allow the transfer of these models to simulate the growth of foodborne contaminants in packaged food.