Synthesis of lactulose in batch and repeated-batch operation with immobilized β-galactosidase in different agarose functionalized supports.
Lactulose synthesis was done in repeated-batch mode with Aspergillus oryzae β-galactosidase immobilized in glyoxyl-agarose (GA-βG), amino-glyoxyl-agarose (Am-GA-βG) and chelate-glyoxyl-agarose (Che-GA-βG), at fructose/lactose molar ratios of 4, 12 and 20. Highest yields of lactulose in batch were obtained with Che-GA-βG (0.21, 0.29 and 0.32g·g-1) for 4, 12 and 20 fructose/lactose molar ratios respectively; when operating in 10 repeated batches highest product to biocatalyst mass ratios were obtained with Am-GA-βG (1.82, 2.52 and 2.7g·mg-1), while the lowest were obtained with Che-GA-βG (0.25, 0.33 and 0.39g·mg-1). Operational stability of Am-GA-βG was higher than GA-βG and Che-GA-βG and much higher than that of the free enzyme, at all fructose/lactose molar ratios evaluated. Efficiency of biocatalyst use for GA-βG were 64.4, 35.5 and 18.4kglactulose/gprotein, for fructose/lactose molar ratios of 4, 12 and 20 respectively, while for Che-GA-βG were 1.46, 1.05 and 0.96kglactulose/gprotein.
School of Biochemical Engineering, Pontificia Universidad Católica de Valparaíso (PUCV), Valparaíso, Chile. Electronic address: c.siancas@gmail.com.
Cecilia
C
Guerrero
Department of Biology, Faculty of Chemistry and Biology, Universidad de Santiago de Chile (USACH), Santiago, Chile.
Carlos
C
Vera
School of Biochemical Engineering, Pontificia Universidad Católica de Valparaíso (PUCV), Valparaíso, Chile.
Andrés
A
Illanes
D001236:Aspergillus oryzae / Q000201:enzymology; D061249:Batch Cell Culture Techniques / Q000379:methods*; D055162:Biocatalysis / Q000187:drug effects; D004795:Enzyme Stability / Q000187:drug effects; D004800:Enzymes, Immobilized / Q000378:metabolism*; D006038:Glyoxylates / Q000494:pharmacology*; D007792:Lactulose / Q000096:biosynthesis*; D012685:Sepharose / Q000494:pharmacology*; D013696:Temperature; D001616:beta-Galactosidase / Q000378:metabolism*
D004800:Enzymes, Immobilized; D006038:Glyoxylates; C070399:glyoxyl agarose; D007792:Lactulose; D012685:Sepharose; D001616:beta-Galactosidase
Enzyme immobilization; Glyoxyl agarose; Heterofunctional supports; Lactulose; Repeated-batch; β-Galactosidase