Optimization of sugarcane factory application of commercial dextranases

The application of commercial dextranases to breakdown dextran in US sugar manufacture is still not optimized, partly because of misinformation about where to add the enzyme and which enzyme to use. Furthermore, there is no uniform method to measure the activity of commercial dextranases by vendors, which has meant that direct comparison of activities has not been possible. A simple titration method to determine the relative activity of dextranases was identified and modified for factory use and activities were confirmed using ion chromatography with integrated pulsed amperometric detection (IC-IPAD). Most commercial dextranases in the US are from Chaetomium gracile or Chaetomium erraticum, and available in “non-concentrated” or “concentrated” forms; an approximately 8- to 10-fold differences in activity exists between the two forms, and variations exist within each form. In 2002 only “non-concentrated” dextranases were applied in Louisiana to either last evaporator syrup or juice. “Non-concentrated” and “concentrated” dextranases at juice pH 5.4-5.8 showed similar maximum activity at 50.0 °C, and activities decreased after 25-30 °Brix. Overall, juice applications were more efficient and economical than adding them to syrups. Application of “non-concentrated” dextranase to evaporator syrup was uneconomical. However, “concentrated” dextranase can be applied to syrup at levels as low as 10 ppm/solids (equivalent to 45 ppm/juice) to remove up to ∼37% dextran, which is useful to consider when severe dextran problems occur. Heating juice to 50.0 °C in the presence of all dextranases dramatically removed more dextran than at the current ambient temperature of application (32.2 °C) and was much more economical. For a “non-concentrated” dextranase, after 10 min at 10 ppm/juice and 50.0 °C, ∼46.3% dextran was removed compared to 13.6% at 32.2 °C. For the “concentrated” dextranase, after 10 min at only 4 ppm/juice, 66.6% dextran was removed at 50.0 °C and was considered an over-dose, compared to 29.6% at 32.2 °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 50.0 °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.