Theoretical simulation
The schematic diagram of a EMR for hydrolysis of dextran is shown inFigure 1 . An initial fouling layer is rapidly formed at the start of the experiment and is assumed to be caused by the deposition of dextranase due to its strong hydrophobic interaction with the membrane9. Since the size of dextranase (13 nm)14 is larger than the membrane pore size (10 nm)10 used in this study, a cake layer would be formed on the membrane surface. After this stage, the dextran and enzyme would attach to each other for dextran degradation and then be deposited on the initial fouling layer. The hydrolyzed small dextran molecules would penetrate through the membrane. The entire filtration stage is therefore assumed to be dominated by the cake filtration mechanism. To facilitate model calculation, the following assumptions were used:
  1. Complete mixing in bulk solution.
  2. Uniform distribution of enzyme and dextran.
  3. The activity of free enzyme is the same as that of the enzyme deposited on the membrane surface. In addition, the enzyme activity is independent of operating conditions.
Figure 1. Schematic diagram of an enzymatic membrane reactor for oligodextran production.