G Eggleston and A Triplett
Audubon Sugar Institute, Louisiana State University Agricultural Center, St. Gabriel, Louisiana, USA; geggleston@agcenter.lsu.edu
Dextranase (endo 1→6–a-glucan hydrolase) enzyme is applied in sugarcane factories to hydrolyse dextran (a-1→6-D-glucan) into smaller, more manageable molecules, which can improve crystallization rates, reduce crystal elongation problems, and prevent dextran penalties in the raw sugar. Reported optimum conditions for the factory application of concentrated dextranase are: Brix <25%, temperature 50 °C, pre-limed juice pH 5.90, 1:10 working solution of concentrated dextranase up to 5 mg/mL dosage, retention time 10 min, and 39 rpm agitation. Because (i) some factories have <10 min juice retention time available and (ii) the relatively high cost of adding dextranase, this small study evaluated and predicted dextran hydrolysis in sugarcane juice (3950 mg/kg Haze dextran content) following the optimum conditions with ≤ 5 mg/mL of concentrated dextranase (92330 DU/mL) and retention times ≤ 5 min. For dextranase concentrations of 4 to 80 mg/L, most of the dextran hydrolysis occurred in the first 1 min, after which there were diminishing techno-economic returns with an increase in retention time and dextranase concentration. At a very low dose of 0.5 mg/L dextranase, little dextran hydrolysis was gained from 1 to 4 min, i.e., 3.1 to 6.7%; ~18-19% hydrolysis of dextran was gained by adding 1.5 mg/L for 4 min or 2 mg/L for 3 min; ~25% hydrolysis of dextran was gained by adding 2 mg/L enzyme for 4 min or 3 mg/L for 3 min. Adding 4 mg/L or 5 mg/L caused hydrolysis of up to ~44% and 51%, respectively, after 4 min.