Starch hydrolysis using α-amylase: A laboratory evaluation using response surface methodology
International Sugar Journal
Sugar Milling Research Institute, University of KwaZulu-Natal, Durban 4041, South Africa
The South African cane sugar mills use a thermostable amylase enzyme (produced by genetically modified strains of Bacillus licheniformis) to control seasonally high starch levels in juice. The recommended point of application of the enzyme is the third or fourth evaporator effect since the temperatures in these effects are high enough for the starch to remain solubilised, but low enough to prevent deactivation of the enzyme. The extended residence time and lower Brix in these effects are also believed to favour enzymatic action compared to conditions in the syrup tank. While considerable effort has been made to characterize the effect of factory parameters on the previous generation of commercially available α-amylases when they were first introduced to the cane sugar industry, not much work has been done on the thermostable enzymes, thus spurring this investigation. The effects and interaction effects of temperature, Brix, pH, starch concentration and enzyme concentration on the amount of starch hydrolysed by the enzyme in a sucrose solution were determined using statistical experimental design techniques. Experiments were conducted as batch processes, while the stirring rate, calcium content and the volume of each run were kept constant. A model was derived and corresponding response surface diagrams were used to identify trends in terms of the evaluated parameters. Some experiments were done to lend support for the model which was shown to be a good predictive tool within the experimental domain investigated.
Bacillus licheniformis; Enzyme concentrations; Genetically modified; Laboratory evaluation; Response surface methodology; Starch concentration; Statistical experimental design; Thermostable enzymes; Bacteriology; Batch data processing; Experiments; Hydrolysis; Starch; Sugar factories; Sugar industry; Surface properties; Amylases; Bacillus licheniformis