Project 4C - Scale-up studies
PI - Brad Saville
As noted in Themes 1 and 2, a key goal of enzyme hydrolysis is to ensure efficient conversion of lignocellulosic feedstocks, with high sugar yields. Successful completion of the bench scale work described in Theme 2 is expected to yield enzymes and enzyme cocktails that satisfy this key objective. However, in a large-scale continuous process, viscosity reduction is also an important objective of the enzymatic hydrolysis step, much in the same way that viscosity reduction is the initial goal during hydrolysis of starch feedstocks. The efficacy of the enzyme cocktails for viscosity reduction can only be observed in larger scale experiments that are more sensitive to the rheological properties of the slurry, so that effects of mixing, heat transfer and mass transfer are more readily detected. Similarly, larger scale fermentation studies are required to test the efficacy of the "selected" or modified microorganisms identified in Theme 3, under conditions more likely to be encountered during industrial processing. In particular, it is critical to ensure efficient fermentation with the pretreated and hydrolysed substrates which are expected to possess the full range of inhibitors. Similarly, the slurry consistency is an important factor when predicting industrially relevant inhibitor concentrations. Finally, larger scale processes can better represent the oxygen tension likely to be encountered during commercial-scale fermentation. Bench scale fermentations can be easily controlled under aerobic or anaerobic conditions, unlike commercial scale fermentations, and therefore, it is critical to establish cell growth and fermentation performance during scale-up.