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Comparison of Galactooligosaccharide Production in Free‐Enzyme Ultrafiltration and in Immobilized‐Enzyme Systems
Author(s) -
Matella N.J.,
Dolan K.D.,
Lee Y.S.
Publication year - 2006
Publication title -
journal of food science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.772
H-Index - 150
eISSN - 1750-3841
pISSN - 0022-1147
DOI - 10.1111/j.1750-3841.2006.00086.x
Subject(s) - chemistry , aspergillus oryzae , immobilized enzyme , chromatography , ultrafiltration (renal) , glutaraldehyde , lactose , enzyme , enzyme assay , biochemistry
Galactooligosaccharides (GOSs) are prebiotics that have been shown to reduce colon cancer risk and enhance immunity. The GOSs can be formed enzymatically from whey lactose using β‐galactosidase, but commercial application has been limited. Free‐ and immobilized‐enzyme recycle batch processes were investigated and compared in this study. Optimum initial conditions were estimated using batch solutions. Using these optimum conditions, an ultrafiltration (UF) free‐enzyme system was developed, and UF fluid pressure (100 to 400 p.s.i.) effect on enzyme performance was studied and compared with a 0 p.s.i. batch control. The optimum conditions were also used to develop an immobilized‐enzyme process using polyethyleneimine (PEI), glutaraldehyde (GA), and cotton cloth. The PEI and GA immobilized agents were studied for their effect on enzyme inactivation. Finally, compatible free‐ and immobilized‐enzyme recycle batch systems were compared for GOS production. Optimum initial enzyme conditions were estimated as 270 g/L initial lactose, 4.5 g/L initial enzyme ( Aspergillus oryzae, 9400 U/g), and 30‐min incubation. Fluid pressure within the free‐enzyme UF membrane system had no significant effect on enzyme performance. The highly agitated UF enzyme system was found to be superior to the less agitated 0 p.s.i batch control. In the immobilization process, approximately 50% to approximately 90% enzyme inactivation was found with the combination of PEI and GA. Equivalent free‐ and immobilized‐enzyme systems showed very similar maximum GOS production of approximately 22% and approximately 20% (w/v) at approximately 15 to 17 min, or 50% conversion for free‐ and immobilized‐systems, respectively.