Agitation effects on submerged growth and product formation of Aspergillus niger

Abstract

Product formation of mycelial organisms, like Aspergillus niger, is intimately connected with their morphology. Pellet morphology is often requested for product formation. Therefore, it is important to reveal the influence of the hydrodynamic conditions on the morphological development. In the present study, pellet morphology and glucoamylase formation were studied under different agitation intensities of A. niger AB1.13. For pellet formation inside the bioreactor, without the use of precultures, it is necessary to work at low energy dissipation rates. Biomass growth and glucoamylase activity were correlated with energy dissipation. Furthermore, product yield was analysed in dependence of pellet size and concentration. The present work shows that simple equations based on Monod-kinetics can describe growth and product formation, in general, also in mycelian organisms. All measured morphological data, like pellet concentration, as well as glucoamylase formation, strongly depend on the hydrodynamic conditions.

Oxygen profiles and biomass distribution in biopellets of Aspergillus niger

“…Furthermore, the number of pellets per volume is a key parameter that will influence product yield (Rinas et al, 2005). As reported by Kelly et al (2004), cultivations of Aspergillus niger, which feature both, high pellet number and small pellet size, show the highest productivity with regard to glucoamylase. Consequently, the challenge for optimization of fungal pellet cultivation is not only to focus on pellet diameter and number of pellets in the early stage of the process, but also on an increase of pellet density, as it is concluded from the results shown.…”

“…Accompanied by lysis in the pellet core, this results in oxygen penetration of the whole pellet. The results presented in Figure 3 are only one possible course of the morphological development of Aspergillus niger, since morphology varies dramatically with cultivation conditions (El-Enshasy et al, 1999;Kelly et al, 2004). However, they point out the large impact of both, pellet morphology and hyphal viability on oxygen gradients.…”

“…Aspergillus niger AB.1.13 (Mattern et al, 1992) is used as model strain for the production of the homologous protein glucoamylase Kelly et al, 2004). It is a uridine auxotrophic and protease deficient strain.…”

Influence of mechanical stress and surface interaction on the aggregation of Aspergillus niger conidia

“…Process design, however, is often hampered by the complex growth pattern of these organisms. There is an entangled relationship between productivity of fungal cultures and the morphologic development, which is affected by several cultivation parameters (Kelly et al, 2004). Many of these parameters are still chosen empirically due to lacking knowledge about the mechanisms governing the morphologic development.…”

Scheinbare Sekretionsverzögerung durch Produktadsorption bei Aspergillus niger

“…B. humane Antikörper-fragmente) erfolgt innerhalb des Sonderforschungsbereiches 578 parallel zur Untersuchung der morphologischen Entwicklung des Pilzes [2,3] und zur Aufklärung und Modellierung von Stofftransport und -umsatz in den kultivierten Biopellets [4,5].…”