CONCEPTUAL AND MATHEMATICAL MODELS OF BATCH SIMULTANEOUS SACCHARIFICATION AND FERMENTATION: DIMENSIONLESS GROUPS FOR PREDICTING PROCESS DYNAMICS

Abstract

This paper describes a modeling effort demonstrating that dimensionless groupings of classical process parameters can be used to predicting process dynamics of batch simultaneous saccharification and fermentation (SSF) processes. Michaelis–Menten enzyme kinetics and Monod growth kinetics were employed, and inhibition of enzyme action and inhibition of microbial growth were neglected. The SSF process was characterized by the relative durations of three phases: A microbially-limited phase, a hydrolysis-limited phase, and a monosaccharide-depletion phase. The duration of these three phases were interrelated, and well predicted by the dimensionless magnitude of the monosaccharide peak (MSP). Thus, the MSP could be used as a single-value descriptor of an SSF process. The dimensionless ratio of the initial hydrolysis rate to the initial substrate consumption rate was shown to predict MSP, and an overall system time constant was shown to predict the total run time of a batch SSF process.