Control of yeast fed-batch process through regulation of extracellular ethanol concentration

Abstract

At high growth rates, the biomass yield of baker's yeast (Saccharomyces cerevisiae) decreases due to the production of ethanol. For this reason, it is standard industrial practice to use a fed-batch process whereby the specific growth rate, mu, is fixed at a level below the point of ethanol production, i.e., mucrit. Optimally, growth should be maintained at mucrit, but in practice, this is difficult because mucrit is dependent upon strain and culture conditions. In this work, growth was maintained at a point just above mucrit by regulating ethanol concentration in the bioreactor. The models used for control design are shown, as are the experimental results obtained when this strategy was implemented. This technique should be applicable to all microorganisms that exhibit an "overflow" type metabolism.

Cole–Cole, linear and multivariate modeling of capacitance data for on-line monitoring of biomass

“…For each batch, the reaction inoculum was obtained by adding one aliquot into a 1-l Erlenmeyer flask containing 100 ml of a sterile complex pre-culture medium (10 g/l yeast extract OXOID, 10 g/l peptone BACTO and 20 g/l glucose) and incubating it for 24 h at 30°C and 200 rpm. The defined culture medium was sterilized by filtration and contained, per liter: 20 g glucose, 5 g (NH 4 ) 2 SO 4 , 3 g KH 2 PO 4 , 0.5 g MgSO 4 9 7H 2 O, as well as trace elements and vitamins (adapted from Verduyn et al [43] and Cannizzaro et al [44]). The medium was supplemented with 0.5 ml/l of a standard antifoam agent to prevent foaming.…”

Control of continuous fed-batch fermentation process using neural network based model predictive controller

“…But, this measurement does not give any indication as to how the glucose is channeled through different pathways. Ethanol concentration in the culture, which can be easily measured by gas chromatography, can also be used to observe the variations in the pathways [28,29]. The biomass concentration control in continuous baker's yeast fermentation was achieved with control of dissolved oxygen concentration by manipulating air flow rate [30] and substrate feed rate [31].…”

State estimation and error diagnosis in industrial fed‐batch yeast fermentation

“…Heat balance has been set up around the fermenters to obtain metabolic heat production rate and included as a redundant measurement, which is rarely available in the literature. [28][29][30][31] After the unmeasured conversion rates are calculated, the best estimate values for the measured conversion rates are obtained by recursive application of the reconciliation method.…”