Morphogenetic and biochemical effects of dissolved carbon dioxide on filamentous fungi in submerged cultivation

Abstract

The inhibitory effects of elevated CO2 in submerged fermentation processes involving bacteria and yeasts have been extensively examined. However, until recently, there have been few similar studies involving filamentous fungi, despite the economic importance of this group of organisms. Many of the investigations that have been carried out have involved inappropriate simulation methods and, as a result, may have overestimated the morphogenetic and biochemical effects of elevated CO2 on filamentous fungi. Recent studies, involving continuous culture of Aspergillus niger and the use of computerised image analysis systems, have allowed a more detailed and accurate description of elevated CO2 inhibition and quantification of the subtler morphogenetic effects. A critical evaluation of the various experimental methods that have been used to simulate, at laboratory scale, what is assumed to occur in large-scale bioreactors is necessary. The review of simulation methods employed has much broader relevance to many other microbial and cell culture systems, emphasising the need to think about the appropriateness and relevance of experimental design.