Abstract
Lactose is a disaccharide found mostly in milk product. Lactose can cause digestive problem that commonly known as lactose intolerant. Manufacturer pre-treated the milk to produce lactose-free milk. This study aims to investigate the effect of impeller design on the rate of reaction of lactose hydrolysis in batch reactor by utilising immobilised enzyme. Lactose hydrolysis reactions were carried out by adding ß-galactosidase (enzyme) into the milk. Alginate was utilised to immobilise the enzyme in order to reuse, enhanced stability and rapid separation of enzymes from the reaction mixture. In this reaction glucose was produced; hence increase sweetness of the milk. Replacing conventional enzymatic processes with immobilised (support) enzyme provides many advantages such as increase the enzyme activity, selectivity, stability and easy recovery from the reaction medium for their reuse. The rate of product formation with different variable such as agitation speed (150 rpm, 250 rpm and 300 rpm) and type of impeller (pitch blade turbine, Rushton turbine, marine propeller and pitch paddle) were investigated. It was found that the highest product formation was with marine propeller at speed 150 rpm with production rate 8.2 mg/L.min, followed by Rushton turbine at speed 250 rpm and pitch blade turbine at speed 300 rpm with production rate 6.2 mg/L.min and 5.4 mg/L.min. Pitch blade shown average of production rate around 3.4 - 4.6 mg/L.min.
