TY - JOUR
T1 - From three-dimensional morphology to effective diffusivity in filamentous fungal pellets
AU - Schmideder, Stefan
AU - Barthel, Lars
AU - Müller, Henri
AU - Meyer, Vera
AU - Briesen, Heiko
N1 - Publisher Copyright:
© 2019 The Authors. Biotechnology and Bioengineering published by Wiley Periodicals, Inc.
PY - 2019/12/1
Y1 - 2019/12/1
N2 - Filamentous fungi are exploited as cell factories in biotechnology for the production of proteins, organic acids, and natural products. Hereby, fungal macromorphologies adopted during submerged cultivations in bioreactors strongly impact the productivity. In particular, fungal pellets are known to limit the diffusivity of oxygen, substrates, and products. To investigate the spatial distribution of substances inside fungal pellets, the diffusive mass transport must be locally resolved. In this study, we present a new approach to obtain the effective diffusivity in a fungal pellet based on its three-dimensional morphology. Freeze-dried Aspergillus niger pellets were studied by X-ray microcomputed tomography, and the results were reconstructed to obtain three-dimensional images. After processing these images, representative cubes of the pellets were subjected to diffusion computations. The effective diffusion factor and the tortuosity of each cube were calculated using the software GeoDict. Afterwards, the effective diffusion factor was correlated with the amount of hyphal material inside the cubes (hyphal fraction). The obtained correlation between the effective diffusion factor and hyphal fraction shows a large deviation from the correlations reported in the literature so far, giving new and more accurate insights. This knowledge can be used for morphological optimization of filamentous pellets to increase the yield of biotechnological processes.
AB - Filamentous fungi are exploited as cell factories in biotechnology for the production of proteins, organic acids, and natural products. Hereby, fungal macromorphologies adopted during submerged cultivations in bioreactors strongly impact the productivity. In particular, fungal pellets are known to limit the diffusivity of oxygen, substrates, and products. To investigate the spatial distribution of substances inside fungal pellets, the diffusive mass transport must be locally resolved. In this study, we present a new approach to obtain the effective diffusivity in a fungal pellet based on its three-dimensional morphology. Freeze-dried Aspergillus niger pellets were studied by X-ray microcomputed tomography, and the results were reconstructed to obtain three-dimensional images. After processing these images, representative cubes of the pellets were subjected to diffusion computations. The effective diffusion factor and the tortuosity of each cube were calculated using the software GeoDict. Afterwards, the effective diffusion factor was correlated with the amount of hyphal material inside the cubes (hyphal fraction). The obtained correlation between the effective diffusion factor and hyphal fraction shows a large deviation from the correlations reported in the literature so far, giving new and more accurate insights. This knowledge can be used for morphological optimization of filamentous pellets to increase the yield of biotechnological processes.
KW - Aspergillus niger
KW - X-ray microcomputed tomography
KW - effective diffusion
KW - filamentous fungal pellets
KW - tortuosity
UR - http://www.scopus.com/inward/record.url?scp=85073927373&partnerID=8YFLogxK
U2 - 10.1002/bit.27166
DO - 10.1002/bit.27166
M3 - Article
C2 - 31508806
AN - SCOPUS:85073927373
SN - 0006-3592
VL - 116
SP - 3360
EP - 3371
JO - Biotechnology and Bioengineering
JF - Biotechnology and Bioengineering
IS - 12
ER -