Abstract

In this study, catabolic repression of tannase in solid-state culture of Aspergillus niger Aa-20 on polyurethane foam was investigated considering the diffusion of a repressor molecule as the main responsible factor. The fundamental hypothesis considers that if repressor molecule uptake rate is higher than repressor molecule diffusion rate on solid matrix, the catabolic repression phenomenon will be minimized. Results showed that addition of low glucose concentrations enhanced the extracellular and intracellular tannase activities (from 5.8 to 6.6 and from 0.96 to 1.76 IU). Besides the glucose uptake rate was higher (1.23 x 10-5 cm2/seg) than glucose diffusion rate on solid matrix (2.8 x 10-6 cm2/seg). On the contrary results at high glucose concentrations, showed that when extracellular tannase activity decreased from 6.6 to 1.87 IU, while intracellular tannase activity was not affected; and under these conditions the glucose diffusion rate governed the process. A particular behaviour was obtained in the repression ratio and the glucose uptake rate/glucose diffusion rate ratio, which permitted to know the sensitivity degree of the culture system, according to the glucose amount added. Substrate diffusion in solid-state culture can be a key factor in its capacity to minimize the catabolic repression of hydrolytic fungal enzymes.

Recommended Citation

Cerda Montalvo, Maria Luisa; Esquivel, Juan Carlos Contreras; Herrera, Raul Rodriguez; and Aguilar, Cristobal N. (2005) "Glucose Diffusion on Support for Solid State Fermentation and its Influence on Tannase Production Profiles," International Journal of Chemical Reactor Engineering: Vol. 3: A5.
Available at: http://www.bepress.com/ijcre/vol3/A5