Ultrafiltration semibatch

During the semibatch experiments, vacuum filtration was applied at 4 d and 8 d after the start of saccharification, to remove the sugar product as filtrate. In selected semibatch experiments, ultrafiltration was applied to the vacuum filtrate to recover soluble enzymes. In other semibatch experiments, the vacuum filter cake was washed extensively with deionized water to remove any enzymes not bound to the solids. After filtration, pretreated corn stover slurry and 7 mL of solution (the ultrafiltration filtrate, or citrate buffer when ultrafiltration was not used) were added to the residual solids and bound enzymes, to replace the volume removed as filtrate during the ultrafiltration step. The additional substrate promotes further saccharification by reusing the cellulase enzymes. To promote further saccharification in a final set of semibatch experiments, additional cellulase at a specific activity of 5 FPU/g of fresh cellulose was added along with the fresh corn stover after vacuum filtration. 

Fig. 1. Glucose concentration over time for semibatch saccharification experiments at 15% (w/w) initial insoluble solids concentration and 20 FPU/g of cellulose enzyme loading. Filtration was applied at two different times to remove glucose (vertical dashed lines). VF Only vacuum filtration was applied alone VF+UF ultrafiltration was also applied following vacuum filtration VF, Washed Vacuum filtration was applied and the filter cake was washed with water. Error bars represent averages 1 SD for two repeated experiments.

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