Optimization of α-amylase application in raw sugar manufacture. Part II: Factory trials

In recent years there have been warnings by some US. refineries that there may be a penalty for high starch concentrations in raw sugar if starch control is not improved. Most commercial α-amylases used by the U.S. sugar industry to control starch have intermediate temperature stability (up to 85°C with an optimum ∼70°C), and are produced from Bacillus subtilis. Full characterization of commercial α-amylases are reported in Part I of this study (Eggleston et al, 2007b). α-Amylase optimization trials in the last evaporator at three factories were conducted across the 2005 Louisiana processing season. Factory 1 typically applied 3.6 ppm/cane wt. of (undiluted) B. subtilis α-amylase with low activity (59 KNU/ml) for an average starch hydrolysis of 6.6% as determined with an iodometric method, that only increased to 11.4% at a 7.2 ppm dosage; similar disappointing results occurred at Factory 3. At Factory 2, the same α-amylase (59 KNU/ml) at 10 ppm (undiluted) gave an average hydrolysis of 25.4% that only increased to 28.5% at 20 ppm. Also at Factory 2, application of a B. subitilis α-amylase of higher activity (5453 KNU/ml) at 2 ppm gave an average hydrolysis of 26.7%, but only increased to 29.6% at 5 ppm because of low contact between the enzyme (a-amylase) and substrate (starch). Application of the α-amylase as a working solution diluted 3-fold in water at the factory, improved contact and starch hydrolysis from 31.9 to 42.0% at 2 and 5 ppm, respectively, and is more cost-effective than adding it undiluted.