A straightforward logistic method for feeding a fed-batch baker's yeast culture

Abstract

The aim of this work was to find a straightforward, low-cost method for nutrient medium delivery during fed-batch cultivation of baker's yeast; a method that provides a high specific growth rate, a high biomass yield, and a high dough-leavening ability. The time profile for the inflow of the nutrient medium, g( t), is a logistic model which takes the form of g( t) = a/(1 + be − ct ), with a, b and c standing for its parameters. The initial values of a, b and c were calculated considering the results of a baker's yeast process where dissolved oxygen tension was used as a control parameter of medium inflow. A method was developed for modifying the parameters of the initial model so as to obtain a formula that would cause the inflow of the nutrient medium to maximize the criterion K( K = Yμ), where Y stands for yeast biomass yield and μ denotes specific growth rate. The parameters of the modified model depended on initial biomass concentration. The relation was described by a logarithmic function and incorporated into the control algorithm. This algorithm produced a biomass yield exceeding 0.55 g g −1 and a high dough-leavening ability. The method proposed is recommendable for small and medium-sized firms producing baker's yeast.