Effect of operating conditions on solid substrate fermentation

Abstract

In this work the effects of environmental parameters on the performance of solid substrate fermentation (SSF) for protein production are studied. These parameters are (i) air flow rate, (ii) inlet air relative humidity, (iii) inlet air temperature, and (iv) the heat transfer coefficient between the outer wall of the fermentor and the air in the incubator. The air flow is supplied to effect cooling of the fermented mass by evaporation of water. A dynamic model is developed, which permits estimation of biomass content, total dry matter, moisture content, and temperature of the fermented matter. The model includes the effects of temperature and moisture content on both the maximum specific growth rate and the maximum attainable biomass content. The results of the simulation are compared with actual experimental data and show good agreement with them. The most important conclusions are that (i) the evaporative cooling of the biomass is very effective for temperature control and (ii) the air flow rate and the heat transfer coefficient have strong effects but they affect the biomass morphology and are not controllable easily. Also, a simple technique for the determination of the optimum temperature and moisture content profile for cell protein production is applied. The simulated biomass production increases considerably employing the optimum temperature and moisture content profiles. The ultimate goal is to implement the determined effects of the environmental parameters on the SSF biomass production and the temperature and moisture variation profiles to effectively control the SSF and optimize the biomass production.

Modeling Menaquinone 7 production in tray type solid state fermenter

“…In subsequent equations we use the true specific growth rate µ G [12], which is the geometric mean of the temperature and water activity specific growth rate parameters:…”

“…To date, most models of ssf bioreactors used this approach to describe the effect of environmental conditions on the parameters of the growth equation [10,12,13,14] although the form of the empirical equation that is used varies. In any case, use of these equations within the kinetic submodel of a bioreactor model has the implicit assumption that the growth of the microorganism depends only on the current values of the environmental variables.…”

A two‐phase model for water and heat transfer within an intermittently‐mixed solid‐state fermentation bioreactor with forced aeration

“…Not surprisingly, given the diculties in controlling bed temperature that are frequently encountered in SSF studies with quantities of substrate of a few kilograms or more, heat transfer within SSF bioreactors has received much attention. Mathematical models incorporating energy balances have been developed for tray bioreactors Modak, 1994, 1995;Smits et al, 1999), packed-bed bioreactors (Saucedo-Castaneda et al, 1990;Mitchell, 1995, 1998;Hasan et al, 1998;Mitchell et al, 1999;Weber et al, 1999;Mitchell and von Meien, 2000), rotating drums (Stuart, 1996), rocking drums (Sargantanis et al, 1993), and intermittently-stirred bioreactors (Ashley et al, 1999).…”

Recent developments in modeling of solid-state fermentation: heat and mass transfer in bioreactors

“…For this reason, the models of these bioreactors focus on the intraparticle processes [26,27], which are discussed elsewhere [2]. The first model proposing water and energy balances for a well mixed forcefully aerated bioreactor was that of Sargantanis et al [28]. More recent developments are described below.…”