P31: Effect of process temperature on fungal morphology in submerged Aspergillus niger processes and its characterization by automated Image Analysis

Many significant industrial fermentation processes utilize filamentous fungi, such as Aspergillus niger and Penicillium chrysogenum, for the production of commercially important products, including most antibiotics, enzymes, food ingredients and organic acids. In their natural habitat, A. niger strains are capable of secreting large amounts of a wide variety of enzymes needed to release nutrients from available biopolymers. This high secretory capacity is exploited by industry for commercial production of enzymes in solid state and submerged fermentation processes. For economic production, most processes require submerged culture in large fermenters, often with intense agitation and aeration. Under these conditions, a wide variation in gross morphology is found, varying from discrete or loosely entangled filaments, the dispersed form, to pellets. Development of fungal morphology and broth viscosity are important factors for cost-efficiency in such processes because they both affect oxygen transfer capacity and the mixing properties of the culture. Within DSM, research has focused on physiological conditions that influence fungal morphology and decrease broth viscosity. In order to characterize fungal morphology development in detail, an in-house Image Analysis system was developed and implemented. Quantitative morphology data were compared with macroscopic broth viscosity, biomass formation and fermentation behavior of a variety of strains. Temperature was one of the process parameters investigated and it was found that a small increase strongly influenced A. niger morphology leading to reduced broth viscosity. Lower viscosity resulted in less stirrer power requirements and lower energy consumption, which is very beneficial in large-scale fungal fermentations.