Immobilization and some properties of commercial enzyme preparation for production of lactulose-based oligosaccharides

The commercial enzymatic preparation, Pectinex Ultra SP-L, was successfully immobilized on activated chitosan particles for production of lactulose-based galacto-oligosaccharide (LuOS). The main degrees of polymerization (DP) of LuOS produced in this bioreactor were DP3 and DP4. The immobilization yield in term of expressed activity and recovery activity were 71% and 36.05%, respectively. The optimum temperature (60° C) was not affected by immobilization process, while the optimum pH was shifted from pH 5.5 to pH 4.5. In addition, a thermal stability of the immobilized enzyme was better than that of free enzyme. The half-life time of hydrolytic activity increased from 2.5 days (free enzyme) to 14 days (immobilized enzyme). Hydrolytic KM values were 651.3 mM and 187.9 mM lactulose for free enzyme and immobilized enzyme, respectively. Furthermore, the immobilized enzyme showed high reusability. The yield of LuOS formation was more than 60% after 33 cycles of reuses. In the case of trans-galactosylation, a model with 8 reaction rates was build using five-step reaction pathways with different initial lactulose concentrations. This catalytic model was validated well for a long-term period (27 days). These results strongly support to develop a continuous bioconversion to synthesize functional food ingredients, prebiotic LuOS.