화학공학소재연구정보센터
Biotechnology and Bioengineering, Vol.118, No.5, 2076-2091, 2021
Machine learning applied for metabolic flux-based control of micro-aerated fermentations in bioreactors
Various bio-based processes depend on controlled micro-aerobic conditions to achieve a satisfactory product yield. However, the limiting oxygen concentration varies according to the micro-organism employed, while for industrial applications, there is no cost-effective way of measuring it at low levels. This study proposes a machine learning procedure within a metabolic flux-based control strategy (SUPERSYS_MCU) to address this issue. The control strategy used simulations of a genome-scale metabolic model to generate a surrogate model in the form of an artificial neural network, to be used in a micro-aerobic fermentation strategy (MF-ANN). The meta-model provided setpoints to the controller, allowing adjustment of the inlet air flow to control the oxygen uptake rate. The strategy was evaluated in micro-aerobic batch cultures employing industrial Saccharomyces cerevisiae yeast, with defined medium and glucose as the carbon source, as a case study. The performance of the proposed control scheme was compared with a conventional fermentation and with three previously reported micro-aeration strategies, including respiratory quotient-based control and constant air flow rate. Due to maintenance of the oxidative balance at the anaerobiosis threshold, the MF-ANN provided volumetric ethanol productivity of 4.16 g center dot L-1 center dot h(-1) and a yield of 0.48 g(ethanol).g(substrate)(-1), which were higher than the values achieved for the other conditions studied (maximum of 3.4 g center dot L-1 center dot h(-1) and 0.35-0.40 g(ethanol)center dot g(substrate)(-1), respectively). Due to its modular character, the MF-ANN strategy could be adapted to other micro-aerated bioprocesses.