Microbial growth, gas production, and volume increase were studied experimentally at 10-degrees-C, 15-degrees-C, 20-degrees-C, 25-degrees-C, and 30-degrees-C in a sourdough production process. Microbial growth was simulated with the logistic equation. Gas production and dough volume increase rates were simulated with the Luede-king-Piret and saturation equations, respectively. In a leavening process, carbon dioxide is produced by the Bakers' yeast and entrapped into the gas cells formed by the gluten films. The microorganisms cannot move in the dough, and therefore the stretching ability of the gas cells and consequently the volume increase and gas production rates depend on the initial number and distribution of the microorganisms in the dough. Temperature increases the specific growth rate and the ratio of final to initial microbial counts, possibly by affecting the diffusion rates of the nutrients to the stationary microorganisms.