Evaluation of strategies for temperature and moisture control in solid state packed bed bioreactors

Different control strategies of bed temperature and moisture were investigated using various inlet air temperatures and air fluxes in both the ordinary packed bed bioreactor (without cooling water in the jacket) and the bioreactor with cooling water in jacket. The experiments were carried out within a 1-L solid-state packed bed bioreactor in which Aspergillus niger was cultivated on wheat bran. On-line measurements of oxygen quantity in the outlet air and temperature of the bed and the inlet air flux were carried out in both types of the bioreactors. Effects of certain control strategies on fungal growth rate were compared in both the bioreactors. According to experimental results, using the bioreactor with the cooling water in the jacket is a better strategy for control of bed temperature and moisture during packed bed solid state fermentation. Cumulative oxygen consumption in this bioreactor was approximately 1.7 times higher than other control strategies used in this study.