Modelling the Growth of Lactic acid Bacteria- Starter Culture for Foods

Abstract

The lactic acid bacteria, Lactococcuslactis, is used as a starter culture(s) in food fermentation(s). The specific growth information can be predicted for such starters, that can be practically valuable in exploiting lactic bacteriafor required fermentations. These bacteria are responsible to produce various metabolites. The metabolites of interest are produced from these starters under a set of known growth conditions. Their growth can be modeled using selected mathematical functions. These functions can be used in determining the parameters like specific growth rate and lag time of the organism under defined environmental conditions. In this study, out of the three functions (Gompertz, Logistic and Richards functions) used, Gompertz function was selected. The model gave out constants that were used to obtain biological parameters for its growth. The main aim was thus to ascertain a particular function and the Goodness of fit (from R2 values) that was measured from the fitted growth data. Durbin-Watson test was used to test the residuals dependency by autocorrelation. A larger number of fd values was the criteria to suggest if either the data plotted on Logistic or Gompertz function (3 parameters functions), was more helpful. The Gompertz function was found to be superior to Logistic function (both being three parameter function), against Richards function (a four parameter function) that had inherent and variable degree of skewness for testing the Gompertz and Logistic functions. The selected function, Gompertz function, was then derivatized and biological parameters were calculated, from the constant values so obtained. Thus the kinetic data with respect to time was resolved into an easy way to calculate biological parameters in terms of the simple equations. This methodology can be extended to lactic acid bacteria producing various other metabolites of interest