Abstract

The dual behavior of Saccharomyces cerevisiae on glucose feed as function of the dilution rate near the critical specific growth rate (µ=0.25) is a bottleneck in industrial production, hence the need for more efficient feeding strategies. In this work novel feeding strategies have been generated and evaluated. For each feeding profile, the 24 h fermentation time was discretized into 7 intervals of 6 then 3 h each. Seven values of µ were selected and fed into the feed flow rate equation, at different time intervals, in a way to maintain a pseudo exponential trend.  Biopro_optimizer, the monitoring and controlling software of the 4-litre bioreactor used, generated nine different feeding strategies for evaluation in fermentation processes. The software also ensured the updating of the feed flow rate every 5 min for 24 h. The control setpoints of the bioreactor were 30°C, 4.5, 200 rpm and 1 vvm for the temperature, pH, agitation and aeration, respectively. The feeding profile with a m sequence  of  0.15, 0.17,0.19 ,0.17, 0.16,0.13 and 0.11 which showed an oscillating exponential increase in feed  flow rate emerged among others with a productivity of 1.80 g/h or a final concentration of  14.25 g/l  from an initial of 0.3 g/l. The obtained data raise the idea of higher biomass productivity of S. cerevisiae in a multiphase strategy with an exponentially oscillating feeding profile.

Key words: Baker’s yeast production, feeding profiles, Biopro_optimizer, fedbatch culture, computer control.