MODELLING OF SOLID STATE FERMENTATION PROCESS

Abstract

Solid State Fermentation involves the fermentation of solid substrates at low water contents. The reduction of bioreactor volume, contamination-level, energy usage and separation costs associated with bioprocesses based on Solid State Fermentation have attracted huge amount of research interest in the past two decades. Packed Bed Solid State Fermentation Bioreactors are one of the most commonly used bioreactor types in Solid State Fermentation processes, due to their simple design and constitution which allows efficient control of air flow rate and temperature. In this thesis, mathematical models have been developed for Packed Bed Solid State Fermentation Bioreactors employing concepts envisaged in Chemical Reaction Engineering. The N-Tanks in Series approach has been utilized to analyze two different situations. The first situation involves the solids and air being considered as a single phase (pseudohomogeneous phase) and in the other situation; they are treated as distinct phases. The primary importance of employing the N-Tanks in Series approach is to demonstrate its successful application to the solution of model equations which avoids the use of complex computational methods like Orthogonal Collocation. It also aids in providing more insights in the design of Packed Bed Solid State Fermentation Bioreactors. The mathematical model developed for the pseudohomogeneous phase considers the production of protease by Penicillum fellutanum and Aspergillus niger. It demonstrates the threat posed by increased temperatures in packed beds to enzyme production and helps in proposing solutions to the problem. The developed mathematical model has been validated with the experimental data of Ghildyal et al. (1994).The mathematical model developed for the two -phase system aids in the exploration of the potential situations to which it can be applied.