Interparticle Space

o soluble hydrolysis product bulk flow (macroscale)

spores at inoculation extending microcolonies surface covered

Fig. 2.7. Changes in biomass distribution during a static SSF process with a fungus. (a) Growth to cover the particle surface during the early phases of the fermentation, shown with an overhead view of the particle surface. (b) Development of aerial and penetrative hyphae during the fermentation, shown with a side view of a cut through two particles with an air space between them

Fig. 2.7. Changes in biomass distribution during a static SSF process with a fungus. (a) Growth to cover the particle surface during the early phases of the fermentation, shown with an overhead view of the particle surface. (b) Development of aerial and penetrative hyphae during the fermentation, shown with a side view of a cut through two particles with an air space between them

Fig. 2.8. Changes that take place during the fermentation with respect to concentration profiles along a radius that extends through the particle into the inter-particle gas phase. The example is given for the growth of a filamentous fungus on a polymeric carbon source, in a situation where the physical structure of the particle is derived from a second, inert polymer, such that the position of the surface does not change. The arrows show the direction of change during the fermentation. The initial concentrations of enzyme and soluble hydrolysis products in the substrate are zero and the initial biomass concentration is typically so small as to be negligible when spore inocula are used. The relative size of the thin liquid film at the particle surface is exaggerated in this diagram. Also, as a simplification, enzyme is assumed to be secreted only at the particle surface. It is assumed that O2 concentrations fall in the inter-particle spaces, although the extent to which this is true will depend on where in the bioreactor this analysis is done. Key: Upper diagram of concentration versus position (-) polymeric carbon source, (---) hydrolytic enzyme, ( ) O2. Lower diagram of concentration versus position (-) biomass, (---) soluble hydrolysis product

Fig. 2.8. Changes that take place during the fermentation with respect to concentration profiles along a radius that extends through the particle into the inter-particle gas phase. The example is given for the growth of a filamentous fungus on a polymeric carbon source, in a situation where the physical structure of the particle is derived from a second, inert polymer, such that the position of the surface does not change. The arrows show the direction of change during the fermentation. The initial concentrations of enzyme and soluble hydrolysis products in the substrate are zero and the initial biomass concentration is typically so small as to be negligible when spore inocula are used. The relative size of the thin liquid film at the particle surface is exaggerated in this diagram. Also, as a simplification, enzyme is assumed to be secreted only at the particle surface. It is assumed that O2 concentrations fall in the inter-particle spaces, although the extent to which this is true will depend on where in the bioreactor this analysis is done. Key: Upper diagram of concentration versus position (-) polymeric carbon source, (---) hydrolytic enzyme, ( ) O2. Lower diagram of concentration versus position (-) biomass, (---) soluble hydrolysis product

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substrate particle moist

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