Optimization of operating volume of microbioreactor using attainable region approach

Abstract

This research project presents the development of a model-based methodology in identifying a suitable (i.e. appropriate) operating volume for a microbioreactor system. Optimization of the microbioreactor operating volume is formulated as a generic optimization problem and solved by decomposing it into five hierarchical stages: (i) pre-analysis, (ii) design target selection, (iii) process design analysis, (iv) final selection and fabrication, and (v) result validation. In the first stage, the concept of attainable region is used to locate the optimal process design solution in terms of optimal condition of operation and economic point of views. The target for this optimal solution is defined and selected at the maximum point of the attainable region diagram. Accordingly the solution target at the maximum point of the attainable region shows the highest value of the objective function, hence the optimal solution for determine the optimum operating volume for the microbioreactor system. Finally, the size and dimension of the optimum microbioreactor is determined and fabricated by using the optimum design value (A = 1.2 ml, 464 µL). The validity of the proposed model-based methodology is confirmed by performing series of fermentation experiments (i.e. conversion of glucose to lactic acid) in threemicrobioreactors setup that was fabricated according to the operating volume suggested at three points located on the attainable region diagram (A= 1.2 ml, B = 1.45 ml, and C = 1.07 ml). The analysis of the biomass concentration profile of glucose in each of the microbioreactor shows that the microbioreactor with design value of point A (i.e. maximum point of attainable region diagram) produced the highest concentration at any interval of fermentation period of six hours. Hence, optimum volume of lactic acid is produced with microbioreactor A. The results obtained confirm the suitability of the proposed model decomposition-based approach (i.e. attainable region approach) for determine the optimum operating volume of microbioreactor before fabrication phase and clear justification for sizes of microbioreactors.