3-03: Investigation of operation strategies and models for continuous Simultaneous Saccharification and Fermentation (cSSF)

Many economic studies assume that continuous Simultaneous Saccharification and Fermentation (cSSF) will be the preferred configuration for commercial applications because it reduces labor costs, has higher productivity, reduces vessel downtime for cleaning and eliminates the need for seed fermentors. But little information is available to guide process design or optimization. And due to the rate limiting of enzymatic hydrolysis especially at low enzyme loadings and high solid loadings and challenge to better match enzyme properties and enhance performance of ethanol fermentation, much improvement must be made for the continuous Simultaneous Saccharification and Fermentation (cSSF) process. Therefore in this study we focused on developing optimal operating strategies based on experiments and kinetic models. The impacts of Enzyme loadings, residence times, organism fermentation features, the number of stages and organism washout are considered for this continuous process. Comparisons are made between batch and continuous processing to understand how end product inhibition and other characteristics differ and their effects on performance. Enzyme loadings and residence times are then selected and applied to establish performance data and results compared to kinetic models to guide definition of preferred operating strategies. The prediction of SSF performance from kinetic models is in good agreement with experiment within 8% glucan loading.