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:
- Complete mixing in bulk solution.
- Uniform distribution of enzyme and dextran.
- 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.