Modeling growth rates as a function of temperature: Model performance evaluation with focus on the suboptimal temperature range

Secondary models, describing the microbial growth rate as a function of temperature, are evaluated with focus on model performance in the suboptimal temperature region. Escherichia coli   K12 MG1655 is considered as the case study. A large set of μmax(T)-estimates is fitted with (1) the cardinal temperature model with inflection (CTMI, Rosso et al., 1993), (2) the square root model (SQRT, Ratkowsky et al., 1983), and (3) the CTMI adapted to describe the particular behavior of Listeria   at suboptimal temperatures (aCTMI, Le Marc et al., 2002). Compared to the CTMI and the SQRT, a more accurate description of the μmax(T)-relation is obtained with the aCTMI, certainly at temperatures below 30 °C. Also, the Tmin estimate is more realistic, i.e., ≈ 6 °C, compared to 8–8.5 °C for the CTMI and SQRT. Use of the aCTMI improved μmax(T)-data description which points at the existence of two phases in the suboptimal temperature region of E. coli   K12. The alternation of the μmax(T) is most likely related to the cold shock response. These results reveal a possible shortcoming of the model structure of commonly used secondary models describing the temperature effect on the microbial growth rate.

► A set of µmax(T)-estimates for E. coli   K12 is fitted with three secondary models. ► The models are studied: (1) CTMI, (2) square root model, and (3) adapted CTMI. ► The most accurate description of the μmax(T)-relation is obtained with the aCTMI. ► This observation suggests the existence of two phases in the suboptimal T-region of E. coli K12. ► The change in the µmax(T)-relation might relate to a switch in the metabolic system.