Enzymatic hydrolysis of starch in a fixed-bed pulsed-flow reactor

One of the most important problems in the design and operation of fixed-bed biological reactors is the control of the process rate by mass-transfer limitations. In order to overcome this problem, a new technology, based on the use of pulsed reactors, was developed. A new type of pulsing device, giving a see-saw-type of disturbance, was assayed. To quantify the possible improvement obtained, we have chosen as an example the hydrolysis of concentrated starch solutions by glucoamylase (from Aspergillus niger) immobilized on chitin slabs. The reactor has an internal diameter of 50 mm and a bed height of 200 mm. Temperature was controlled at 25°C, and the working hydraulic retention times were from 0.29 to 1.8 h. The results revealed that pulsation helps to lessen the diffusional difficulties, since the maximum reaction velocity increased 10%. Additional improvements, up to 20% in some cases, are achieved by recycling a part of partially converted feed.