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This paper tests different control strategies based on classic proportional integral derivative (PID) and advanced dynamic matrix control (DMC) algorithms for an intermittently stirred, forcefully aerated solid-state fermentation bioreactor. The study was done using a distributed parameter model to reproduce the main operating features of this type of bioreactor. There is predicted to be a remarkable improvement in the bioreactor productivity when control strategies are implemented. For this type of bioreactor, the temperature and water content of the substrate bed can be controlled by saturating the air at the air inlet but manipulating its temperature, coupled with a strategy of water replenishment when the water content of the bed falls below a threshold. Dynamic matrix control is superior to PID control; however, a specific convolution matrix for different stages of the fermentation is necessary due to the changing behavior of the system. This work shows the benefit of mathematical modeling, since the many different operating conditions investigated via simulations would not have been economically feasible to undertake experimentally with a large-scale bioreactor. The results obtained provide an excellent starting point for such large-scale experimental work.

In this work a method of analyzing the performance of solid-state fermentation bioreactors is described. The method is used to investigate the optimal value for the spacing between the cooling plates of the Zymotis bioreactor, using simulated fermentation data supplied by a mathematical model. The Zymotis bioreactor has good potential for those solid-state fermentation processes in which the substrate bed must remain static. The current work addresses two design parameters introduced by the presence of the internal heat transfer plates: the width of the heat transfer plate, which is governed by the amount of heat to be removed and the pressure drop of the cooling water, and the spacing between these heat transfer plates. In order to analyze the performance of the bioreactor a productivity term is introduced that takes into account the volume occupied within the bioreactor by the heat transfer plates. As part of this analysis, it is shown that, for logistic growth kinetics, the time at which the biomass reaches 90 % of its maximum possible value is a good estimate of the optimum harvesting time for maximizing productivity. Application of the productivity analysis to the simulated fermentation results suggests that, with typical fast growing fungi ( = 0.324 h–1), the optimal spacing between heat transfer plates is of the order of 6 cm. The general applicability of this approach to evaluate the productivity of solid-state bioreactors is demonstrated., Opisana je metoda analize rada fermentacijskog bioreaktora sa čvrstim slojem. Postupak je primijenjen da bi se ispitala optimalna vrijednost za razmak između ploča za hlađenje u bioreaktoru Zymotis, koristeći simulirane fermentacijske podatke dobivene prema matematičkom modelu. Bioreaktor Zymotis je vrlo prikladan za one fermentacijske procese u čvrstom sloju u kojima supstratni sloj mora ostati statičan. Opisani postupak koristi dva određena parametra uvjetovana prisutnošću internih ploča za prijenos topline. Širina ploča za prijenos topline uvjetovana je količinom topline koju treba uklonitii padom tlaka rashladne vode te razmakom između tih ploča. Da bi se analizirao učinak bioreaktora, uveden je pojam produktivnosti koji uzima u obzir volumen unutar bioreaktora što ga zauzimaju ploče za prijenos topline. Kao dio ove analize pokazalo se da je, prema logistici kinetike rasta, optimalno vrijeme za povećavanje produktivnosti upravo ono kada biomasa postiže 90 % svoje maksimalne moguće vrijednosti.