Fed-batch operation for the synthesis of lactulose with β-galactosidase of Aspergillus oryzae.
Fed-batch synthesis of lactulose from lactose and fructose with Aspergillus oryzae β-galactosidase was evaluated, obtaining a concentration of 40.4g·L-1, which is 20% higher than obtained in batch, while the concentration of transgalactosylated oligosaccharides (TOS) was reduced by 98%. Therefore, selectivity of lactulose synthesis can be significantly higher by operating in fed-batch mode. The enzyme-limiting substrate mass ratio (E/S) is a critical variable in fed-batch operation. Higher values favor lactose hydrolysis over transgalactosylation, being 400IU/g the limit for proper lactulose synthesis in fed-batch operation. Selectivity of lactulose synthesis increased with E/S being quite high at 800IUH·g-1or higher. However, this increase was obtained at the expense of lactulose yield. Lactulose synthesis in fed-batch operation was a better option than conventional batch synthesis, since higher product concentration and selectivity of lactulose over TOS synthesis were obtained.
School of Biochemical Engineering, Pontificia Universidad Católica de Valparaíso (PUCV), Valparaíso, Chile.
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. Electronic address: aillanes@pucv.cl.
Andrés
A
Illanes
D001236:Aspergillus oryzae; D007785:Lactose; D007792:Lactulose; D009844:Oligosaccharides; D001616:beta-Galactosidase
D009844:Oligosaccharides; D007792:Lactulose; D001616:beta-Galactosidase; D007785:Lactose
Aspergillus oryzae; Batch operation; Fed-batch operation; Lactulose; β-Galactosidase