Modelling sequential co-inoculation of a non-conventional biocontrol yeast and <i>Saccharomyces cerevisiae</i> in wine

Microbial interactions play a decisive role in fermentation dynamics and final wine quality. The sequential co-inoculation of non-conventional yeasts with Saccharomyces cerevisiae has been proposed as a strategy to enhance organoleptic properties, reduce ethanol content and/or exert biocontrol over spoilage yeasts, thereby decreasing the use of sulphur dioxide (SO2). Among these species, Wickerhamomyces anomalus has shown effectiveness; however, its interaction with S. cerevisiae under sequential inoculation schemes has not been explored from an ecological modelling perspective. In this study, the population dynamics of both species were analysed using an Ordinary Differential Equation (ODE)-based model, evaluating the influence of co-inoculation timing, temperature, and SO2 concentration to maximise the viability of the biocontrol yeast without affecting the fermentative kinetics of S. cerevisiae. Fifteen fermentations were carried out following a Box–Behnken experimental design, varying temperature (15–20 °C), molecular SO2 (0–0.2 ppm), and co-inoculation time (0–48 h). A Gilpin–Ayala competition model was applied, incorporating secondary temperature models (Arrhenius and Ratkowsky) and constant parameters for the effects of SO2 and co-inoculation time. The model was refined through parameter estimation and the Akaike Information Criterion (AIC), and was experimentally validated under different inoculum proportions. The iterative fitting process led to a simplified Lotka–Volterra model modified solely to include the effect of co-inoculation time. Inoculating S. cerevisiae 48 h after W. anomalus significantly increased the viability of the latter (by 75 % compared to simultaneous inoculation) without affecting fermentative kinetics. Simulations confirmed the final dominance of S. cerevisiae and the convergence of both populations toward the same sink point. Delaying S. cerevisiae inoculation favoured the early establishment of W. anomalus, enhancing biocontrol efficacy without compromising alcoholic fermentation. This simplified ecological model provides a framework to optimise microbial management in winemaking, reduce SO2 usage, and promote more sustainable fermentation processes.