An experimental study of acid production rate controlled operations of a continuous fermentor

Abstract

The efficacy of acid production rate (APR) controlled operations of a continuous fermentor supporting the growth of a methylotroph, L3, was experimentally examined. Direct digital control of pH at a constant value allowed for on-line estimation of APR during the fermentation. Two types of APR controlled operations were studied. In the first type of operation, the APR was controlled at a constant value according to a predetermined program by manipulating the feed flow rate to the fermentor. Such an operation effectively stabilized the cell mass productivity of a continuous fermentor subjected to disturbances in the feed nutrient concentration. It resulted in a near complete conversion of methanol to yield a cell mass product with very low amounts of unutilized methanol at both steady state and transient fermentation situations. In the second type of operation, the feed flow rate was manipulated to optimize the steady state value of APR during the fermentation. This method shows promise for on-line steady state optimization of cell mass productivity in a continuous fermentor.