Postharvest quality and processing of sugarcane and sweet sorghum for sugar and ethanol production
Location: Commodity Utilization Research
Title: Optimization of alpha-amylase application in raw sugar manufacture
Submitted to: Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: September 18, 2006
Publication Date: September 20, 2006
Citation: Eggleston, G., Montes, B., Monge, A., Guidry, D. 2006. Optimization of alpha-amylase application in raw sugar manufacture. In: Proceedings of the 2006 Sugar Processing Research Conference, September 17-20, 2006, Sao Pedro, Brazil. p. 319-340.
In recent years there have been warnings by some U.S. refineries that there may be a penalty for high starch concentration sin raw sugar if starch control is not improved. Most commercial alpha-amylases used by the U.S. sugar industry to control starch have intermediate temperature stability (up to 85 degrees C with an optimum-70 degrees C), and are produced from Bacilllus subtilis. There is neigher a uniform/standard method to measure the alpha-amylase activity in the sugar industry nor a regulatory body to issue or regulate standard activity methods and units for any commercial enzyme. A method incorporating Phadebus TM blue starch tablets was modified to simulate conditions in typical last evaporators, i.e., pH 6.4 and 65.5 degrees C, where alpha-amylases are mostly applied. A wide range of activity existed for alpha-amylases (59.0 to 544.3 KNU/ml) that did not reflect their comparative unit costs, i.e., activity per U.S. dollar only differed 4-fold from 40.7 to 161.8 KNU/ml/$. Alpha-Amylase optimization trials in the last evaporator at three factories were conducted across the 2005 Louisiana processing season. Factory 1 typically aplied 3.6 ppm/cane wt. of (undiluted) B. subtilis alpha-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 alpha-amylase (59 KNU/ml) at 10 ppm (undiluted) gave an average hydrolysis of 25.4% that only increased to 28.5% at 20 ppm. Application of a B. subtilis alpha-amylase of higher activity (545.3 KNU/ml) at 2 ppm gave an average hydrolysis of 26.7%, but only increased to 29.6% at 4 ppm because of low contact between the alpha-amylase and starch. Application of the alpha-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 additing it undiluted. Concern about the use of engineered high temperature stability (up to 115 degrees C) alpha-amylases from Bacillus licheniformis and stearothermophilus, developed for larger markets than the sugar industry, and possible carry-over activity into raw and refined sugard, molasses, and food products, are discussed.