Temperature-dependent growth kinetics of Lacticaseibacillus rhamnosus GG in oat-based milk alternative

Microbial growth responses of probiotic Lacticaseibacillus rhamnosus GG with well-documented health effects were studied in an oat-based milk alternative in the biokinetic temperature range of 8 to 44 °C. The applied Baranyi model (with a fixed parameter value h₀ = 0.407) fitted the growth data well, as shown by the goodness of fit measures (R² = 0.995; RMSE = 0.153) for the total experimental data set (n = 245). Using the initial inoculations of 2.7 ±0.1 log CFU.ml⁻¹, the maximal population density (MPD) of 8.3 ±0.4 log CFU. ml⁻¹ was reached in stationary phase in the temperature range from 12 to 37 °C. Slightly lower MPDs were recorded at higher temperatures, 40 and 44 °C, while an increase in only 1 log was reached at 8 °C. Thus, the MPD 3.7 log CFU.ml⁻¹ was only estimated. Based on the experiments, the highest specific growth rate (μ_max) of 0.800 ⁻¹ and the shortest lag phase (λ) of 0.51 h were observed at 40 °C. The Ratkowsky modified square root model (mSQRT) was used in the secondary modelling for μ_max values and the cardinal parameters minimum and maximum temperature were determined: T_min = 4.2 °C; T_max = 47.8 °C. As drinks of plant origin are produced in large volumes, the production of their fermented varieties is expected to appear in a short time. This is why providing parameters on kinetic behaviour of L. rhamnosus GG is essential for industrial process design and further scale up of fermented dairy-free matrice with probiotic potential.