A three-dimensional discrete lattice-based system for modeling the growth of aerial hyphae of filamentous fungi on solid surfaces: A tool for investigating micro-scale phenomena in solid-state fermentation

In solid-state fermentation systems, the growth of aerial hyphae into the interparticle spaces increases the pressure drop through forcefully aerated beds. Aerial hyphae can also bind particles into agglomerates, restricting the transfer of O2 to the particle surfaces. Despite these important effects, to date relatively little effort has been made to understand the growth patterns of these hyphae. In the current work we present a discrete lattice-based model that can be used to simulate the growth of the aerial hyphae of filamentous fungi. In the model, the elongation of hyphae involves the successive addition of 10 μm cubes, with random numbers being used to choose the direction of growth. The model was able to describe profiles available in the literature for the density of the aerial hyphae, as a function of height above the surface, for a situation in which the filamentous fungus Rhizopus oligosporus was grown on potato dextrose agar. The model can be modified to describe various different situations involving the growth of filamentous fungi in solid-state fermentation systems, such as the growth of penetrative hyphae and the growth of hyphae within the wet mycelial layer that often forms at the surfaces of particles. It therefore represents a useful tool for investigating phenomena that occur at the micro-scale in solid-state fermentation systems.

Research highlights
► We developed a model for describing the growth of aerial hyphae of filamentous fungi.
► The model is lattice-based but has a flexibility similar to lattice-free models.
► The model can describe experimental profiles for the density of aerial hyphae.
► It can be used to explore micro-scale phenomena in solid-state fermentation.