A computer model for the growth and differentiation of a fungal colony on solid substrate.

Mold growth and differentiation are closely related to the formation of secondary products. In solid-substrate fermentations this interrelationship is often more completely realized than in submerged cultures. Solid substrate reactions are used commercially in a limited manner in the western world, but are relatively common in Asia. Basic studies in solid-substrate fermentation should yield results applicable to all types of commercial mold fermentations for the production of a secondary product. This paper presents a relatively simple model for the growth of a mold colony on a solid surface with a defined medium utilizing glucose. Unlike submerged cultures the model must account for both cellular differentiation and the spatial heterogeneity in the system. Model parameters were estimated independently using literature values. The results of the simulation studies suggest that mass transfer limitations are at least partially responsible for the proliferation of differentiated structures on solid substrates as compared to liquid cultures. Since the concentration profile depends on the depth of the substratum, conditions that enhance conidia production can be achieved by controlling the depth of the solid medium.