Novel feeding strategies for Saccharomyces cerevisiae DS2155, using glucose limited exponential fedbatch cultures with variable specific growth rates (m)

Abstract

The dual behavior of Saccharomyces cerevisiae on glucose feed as function of the dilution rate near the critical specific growth rate (ì=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 ì 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.