In this work, an expert system was developed and applied for on-line control and supervision of ethanolic d.w. fermentation by immobilized Saccharomyces cerevisiae in F a fixed-bed pulsed bioreactor of 1.2 1 of working volume. A number of experiments with different substrate concentra-Fg tions (75, 100, 150 and 200 g/l) and hydraulic residence times f (2.4, 1.2 and 0.8 h) were carried out.
HRT Knowledge-based computer-aided supervision of this pro-k cess involves accurate on-line measurement of the relevant O~ process variables (temperature, pH, flow rate, carbon dioxide Qs production, etc.). Carbon dioxide production was used for the So estimation of the ethanol productivity. The analysis of the t measured data allowed to detect states or trends that may be to indicative of process or system failures, providing advices ts and/or alarms.
Ye/s The results showed the reliability of the control system. In u previous works, it was proven that pulsing the feed stream highly improves the productivity of fermentation processes carried out in fixed-bed bioreactors [ 14, 15, 16]. The amplitude and frequency of the pulsation, which is a key factor in the performance of a pulsed feed bioreactor [13], was selected by the control system by using an algorithm allowing the ethanol productivity to be optimized.
The pulsation frequency which maximizes the ethanol productivity, presents a high dependency on the hydraulic residence time and the feeding substrate concentration. When increasing the substrate concentration the optimum pulsation frequency also increases; when increasing the hydraulic residence time the optimum pulsation frequency decreases.