Bioreactors and engineering of filamentous fungi cultivation

Abstract

Filamentous fungi have been growingly used to produce many compounds we use on a daily basis, such as antibiotics and enzymes, or even to treat industrial effluents. While some of these processes have been established for decades, the rise of new production platforms combined with the continuous development of traditional processes makes fungal biotechnology a current trend. A key element in fungal biotechnology is the bioreactor design, which may critically affect its performance and the economics of the process. This chapter addressed the main engineering aspects on the selection and design of bioreactors for submerged filamentous fungi cultivations. Medium rheology, oxygen transfer, and shear stress showed to be intimately related to the efficiency of these processes, becoming obvious factors to consider at bioreactor selection. The main bioreactor designs typically employed on these processes were briefly discussed with a special emphasis on submerged culture processes. Some of the most important engineering aspects were framed under the scope of the main reactor configurations, being established the main advantages and key operational challenges. Although traditional designs such as the stirred tank reactor and bubble columns are still predominantly used, new configurations have been developed, namely under the solid-state fermentation concept, looking to surpass some of the typical issues found on these systems such as shear stress and inefficient aeration. Finally, fungal morphology was discussed in relation to how it is related to different aspects of reactor selection, highlighting how each one affects the other. Mixing mechanisms showed a critical relation with fungal morphology, becoming one of the key aspects to address in future bioreactor developments.