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Beet sugar syrup and molasses as low-cost feedstock for the enzymatic production of fructo-oligosaccharides

Ghazi, I., Fernandez-Arrojo, L., Gomez de Segura, A., Alcalde, M., Plou, F.J., Ballesteros, A.
Journal of agricultural and food chemistry 2006 v.54 no.8 pp. 2964-2968
beet sugar, molasses, syrups, enzymatic treatment, pectinesterase, polygalacturonase, Aspergillus aculeatus, immobilized enzymes, synthesis, fructooligosaccharides, feed additives
Sugar syrup and molasses from beet processing containing 620 and 570 mg/mL sucrose, respectively, were assayed as low-cost and available substrates for the enzymatic synthesis of fructo-oligosaccharides (FOSs). A commercial pectinase (Pectinex Ultra SP-L, from Aspergillus aculeatus) characterized by the presence of a transfructosylating activity was used as a biocatalyst. The FOS production increased when lowering the initial pH value of syrup (7.5) and molasses (8.9) to 5.5. Sugar syrup and molasses were diluted in order to reduce substrate viscosity; interestingly, the percentage of FOS with regards to total sugars remained almost constant, which indicated a high transferase-to-hydrolase ratio for this enzyme. Kinetics of FOS production was analyzed. Using approximately 10 U transfructosylating activity per g sucrose, the FOS concentration reached a maximum of 388 mg/mL after 30 h using syrup and 235 mg/mL in 65 h with molasses. These values corresponded to approximately 56 and 49% (w/w), respectively, of the total amount of carbohydrates in the mixture. The enzyme was also covalently immobilized on an epoxy-activated polymethacrylate-based polymer (Sepabeads EC-EP5). We found that immobilized Pectinex Ultra SP-L can be efficiently applied to the synthesis of FOS using syrup and molasses as substrates.