Submitted to: Process Biochemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/29/2004
Publication Date: 2/1/2005
Citation: Eggleston, G., Monge, A. 2004. Optimization of sugarcane factory application of commercial dextranases. Process Biochemistry. 40(5):1881-1894.
Interpretive Summary: Enzymes named dextranases have been used in U.S. sugar manufacture to break down unwanted dextran into smaller, more managable molecules. However, dextranase application is still not optimized because of misinformation about where to add the enzyme and which enzyme to use. In this study, a simple titration method to determine the relative strength of dextranases was identified and modified for easy factory use. Commercial dextranase enzymes in the U.S. were shown to be available in 'non-concentrated' or 'concentrated' forms, with an approximate 8-10 fold difference in strength exists between the two concentration forms, with the concentrated dextranase having better storage properties. Overall, juice applications were more efficient and economical than adding them to evaporator syrups. Application of 'non-concentrated' dextranase to evaporator syrup was uneconomical, although 'concentrated' dextranase can be applied to syrup. Heating juice to 48.9oC in the presence of all dextranases, dramatically removes more dextran from cane juice, and it was more economical to add the concentrated dextranase than the non-concentrated to juice. Costly sugarcane deterioration is increasing in Louisiana because if is now being harvested into shorter pieces than long stalks. Furthermore, the Louisiana sugarcane industry is under the threat of reducing or stopping all burning which means more sugarcane trash (leaves and tops) is being delivered at factories that detrimentally affects processing. This work presents a comprehensive review of several phases of work to better understand and monitor sugarcane deterioration by researchers and factory staff. This work will impact scientists, giving them a way to better confirm sugarcane deterioration, and also sugarcane farmers and factory processors by letting them know how to better harvest, handle and store cane, in order to reduce deterioration.
Technical Abstract: The application of commercial dextranases to breakdown dextran in U.S. sugar manufacture is still not optimized, partly because of misinformation about where to add the enzyme and which enzyme to use. In this study, a simple titration method to determine the relative activity of dextranases was identified and modified for easy factory use. All activities were confirmed with an accurate IC-IPAD method using a NaOH/NaOAc gradient. Most commercial dextranase enzymes in the U.S. are from a fungal source: Chaetomium gracile or erraticum, and are available in 'non-concentrated' or 'concentrated' forms. An approximate 8-10 fold difference in activity exists between the two concentration forms, and activity variations exist within each form. In 2002/03 only 'non-concentrated' dextranases were applied in Louisiana to either last evaporator bodies (usually '10ppm/syrup) or juice. 'Non-concentrated' and 'concentrated' dextranases studied at juice pH 5.4-5.8, showed similar max. activity at 48.9 degrees C or 120 degrees F, as monitored by IC. Dextranase activities, in last evaporator syrup temperature (~63 degrees C or 145 degrees F) and Brix (~65 degrees) conditions, were dramatically reduced (activity began to decrease after 25-30 degrees Brix). Overall, juice applications were more efficient and economical than adding them to evaporator syrups. Application of 'non-concentrated' dextranase to evaporator syrup was uneconomical. However, 'concentrated' dextranase can be applied to syrup at levels as low as 10ppm/solids (equiv. to 45ppm/juice) to remove up to ~37% dextran which is useful to consider when severe dextran problems occur. Heating juice to 48.9 degrees C in the presence of all dextranases, dramatically removed more dextran (3380ppm/oBrix) from a juice than at the current ambient temperature of application (32.2 degrees C or 90 degrees F) and was much more economical. For a 'non-concentrated' dextranase, after 10min at 10ppm/juice and 48.9 degrees C, ~46.3% dextran was removed compared to 13.6% at 32.2 degrees C. For the 'concentrated' dextranase, after only 10 minutes at only 4 ppm/juice, 66.6% dextran was removed at 48.9 degrees C and was considered an overdose, compared to 29.6% at 32.2 degrees C. Dextranase was shown to work in the presence of dithiocarbamate biocide in juice, and factory studies are being undertaken to check that no adverse dextran formation is occurring at 48.9 degrees C. Under factory storage conditions, over a grinding season (90 days), the activity of 'concentrated' dextranase decreased only slightly (~9%), whereas 'non-concentrated' dextranase activity had approximately halved (~46%), and even reduced in activity when stored under refrigeration.