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Use of immobilised raffinase

The development of a raffinase (a-D-galactosidase) suitable for commercial use is another triumph of enzyme technology. Plainly, it would be totally unacceptable to use an enzyme preparation containing invertase to remove this material during sucrose production (see Chapter 4). It has been necessary to find an organism capable of producing an a-galactosidase but not an invertase. A mould, Mortierella vinacea var. raffinoseutilizer, fills the requirements. This is grown in a particulate form and the particles harvested, dried and used directly as the immobilised-enzyme preparation. It is stirred with the sugar beet juice in batch stirred tank reactors. When the removal of raffinose is complete, stirring is stopped and the juice pumped off the settled bed of enzyme. Enzyme, lost by physical attrition, is replaced by new enzyme added with the next batch of juice. The galactose released is destroyed in the alkaline conditions of the first stages of juice purification and does not cause any further problems while the sucrose is recovered. This process results in a 3% increase in productivity and a significant reduction in the costs of the disposal of waste molasses.

Immobilised raffinase may also be used to remove the raffinose and stachyose from soybean milk. These sugars are responsible for the flatulence that may be caused when soybean milk is used as a milk substitute in special diets.

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