Full Length Research Paper

Experimental study of the production of biomass by Sacharomyces cerevisiae in a fed batch fermentor

M.O. Daramola^{1, 2}* and L. Zampraka¹

¹Bioprocess Engineering Department, Wageningen University and Research Centre, The Netherlands.

²Department of Process Engineering, Stellenbosch University, Private Bag X1, Matieland 7602, Stellenbosch, South Africa.

*Corresponding author. E-mail: daramola@sun.ac.za.

Nomenclature:, Amount of biomass (mol);, stirrer speed (rpm); , gas flow rate (m³/s); , oxygen uptake (consumption) rate (mol/s); , maximum oxygen uptake (consumption) rate (mol/s); , stirrer power (J/s); , pressure above the stirrer (bar); , pressure at the prevailing condition in the fermenter (bar); , oxygen transfer coefficient (m/s); , gas velocity (m/s); , volume of the liquid (m³); , oxygen concentration (mol/m³); , critical oxygen concentration (mol/m³); , oxygen concentration in the off gas; , oxygen concentration in the inlet gas; , specific growth rate (h^-1); and , maximum specific growth rate (h^-1).

Accepted 26 November, 2007

The aim of this study is to investigate production of Baker’s yeast using a theoretically programmed fed-batch fermentor to produce as much as possible Baker’s yeast biomass using a minimal amount of substrate with low energy for stirring and aerating. Theoretical data obtained through material balance and kinetics equations were compared with experimental data and possible disagreements discussed with possible physical explanations. The result showed that the experimental biomass yield is greater than the theoretical one. An experimental yield of 92.2% was obtained for growing 191 mol of biomass with 207.8 mol of sugar with low oxygen uptake rate. Also, the obtained specific growth rate (μ) of 0.39 h^-1 exceeds by far the maximum specific growth rate of the yeast under aerobic condition as obtained theoretically.

Key words: Fermentation, aerobic, fed-batch, yeast, Crabtree.