The higher porosity of the 0.39 mm particles benefited aeration
and dissipation of gases and heat produced during microbial
growth. During the filamentous fungi growth on solid substrates,
it is generally accepted that there is a limitation in oxygen supply
to the cells that are in close contact with the substrate or that penetrate
the substrate. For example, in the case of the fungus Aspergillus
oryzae, oxygen is mainly (70%) absorbed by the aerial
hyphae