SIMULATION OF GROWTH OF A FILAMENTOUS FUNGUS IN 3 DIMENSIONS

The tridimensional growth of a filamentous fungus was simulated, based on a model for the evolution of the microscopic morphology of Trichod erma reesei. When supplemented with a spatial representation of growth , the model correctly simulates the evolution from a single spore to a pellet. Diffusion of oxygen is included in the model. The simulated t ridimensional structures have a fractal nature; and the fractal dimens ion, determined by a box-counting method, increases during growth. The fractal dimension only depends on the mass of the pellet and is not a ffected by model parameters such as tip extension rate and branching f requency. Realistic pictures are obtained and the radius of the pellet increases at a constant rate. The influence of model parameters (tip extension rate, branching frequency, minimum porosity) on dissolved ox ygen concentration profiles, biomass concentration profiles, rate at w hich the pellet diameter increases, and the evolution of the fractal d imension was determined. The dissolved oxygen profiles were found to b e very different from the profiles, obtained by assuming a homogenous biomass distribution within the pellet. Finally, the formation of pell ets from spore aggregates is calculated and the size of the spore aggr egate is found to only influence the time needed before the appearance of a pellet and not its morphology. (C) 1997 John Wiley & Sons, Inc.