Figure 9.13 and 9.14 give an overview of the overall plant and the process control
room. Rapid optimisation of different esterification reactions catalysed by Novozym 435
was performed using a thermodynamic approach to the system. The first step was the
determination of the āGĀ° of each targeted reaction. Rapid kinetic experiments and
stability tests were subsequently performed in order to determine the limits of important
parameters such as acid and alcohol thermodynamic activities, operating temperature and
pressure, and initial water requirement. In the second step, optimisation of the operating
parameters within the possible range of each parameter was realized, using calculation
predictive sheets developed for this purpose. When theoretical optimisation was
performed, a sample test production began based on the production of 200 g of ester on a
lab scale experimental setup at 1/1000 scale of the platform. These sample productions
were carried out over a minimum period of 24 to 100 hours in order to check the stability
of the enzymatic activity concurrently. Figure 9.15 gives an example of stability under
optimised conditions and half life time was found to be around 2000 hrs. Once the sample
test was performed, large-scale production was engaged at the level of 100 to 200 kg of
ester.
While it was unproven ten years ago, the technological feasibility of solid/gas
bioprocesses at the pre-industrial level has now been demonstrated, and economical
studies have shown that they are competitive.
Test productions of large quantities of product by solid/gas catalysis have been
performed, and the gas/solid system technology proved its ability to efficiently perform
esterification reactions while at the same time greatly simplifying the downstream
process
Solid/gas systems, theory and applications 281