Repeated-batch operation for the synthesis of lactulose with β-galactosidase immobilized by aggregation and crosslinking.
Synthesis of lactulose under repeated-batch operation was done with cross-linked aggregates of Aspergillus oryzae β-galactosidase (CLAGs). The effect of the crosslinking agent to enzyme mass ratio and cross-linking time were first evaluated. Best results were obtained at 5.5gdeglutaraldehyde/g enzyme at 5h of cross-linking, obtaining a specific activity of 15,000IUg(-1), with 30% immobilization yield. CLAG was more stable than the free enzyme under non-reactive conditions with a half-life of 123h at 50°C and when operated in repeated-batch mode, yield and productivity was 3.8 and 4.3 times higher. Maximum number of batches was determined considering biocatalyst replacement at 50% residual activity. 98 and 27 batches could be performed under such criterion at fructose/lactose molar ratio of 4 and 20 respectively, reflecting that enzyme stability is strongly affected by the sugars distribution in the reaction medium.
School of Biochemical Engineering, Pontificia Universidad Católica de Valparaíso, Avenida Brasil 2147, Valparaíso, Chile. Electronic address: c.siancas@gmail.com.
Cecilia
C
Guerrero
School of Biochemical Engineering, Pontificia Universidad Católica de Valparaíso, Avenida Brasil 2147, Valparaíso, Chile.
Carlos
C
Vera
School of Biochemical Engineering, Pontificia Universidad Católica de Valparaíso, Avenida Brasil 2147, Valparaíso, Chile.
Erick
E
Araya
School of Biochemical Engineering, Pontificia Universidad Católica de Valparaíso, Avenida Brasil 2147, Valparaíso, Chile.
Raúl
R
Conejeros
School of Biochemical Engineering, Pontificia Universidad Católica de Valparaíso, Avenida Brasil 2147, Valparaíso, Chile.
Andrés
A
Illanes
D001236:Aspergillus oryzae / Q000201:enzymology; D003432:Cross-Linking Reagents / Q000737:chemistry; D004789:Enzyme Activation; D004800:Enzymes, Immobilized / Q000737:chemistry; D005632:Fructose / Q000737:chemistry*; D007785:Lactose / Q000737:chemistry*; D007792:Lactulose / Q000138:chemical synthesis*; D001616:beta-Galactosidase / Q000737:chemistry*
D003432:Cross-Linking Reagents; D004800:Enzymes, Immobilized; D005632:Fructose; D007792:Lactulose; D001616:beta-Galactosidase; D007785:Lactose
Enzymatic synthesis; Immobilized enzyme; Lactulose; Repeated-batch; β-Galactosidase