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Title: Enzymatic synthesis of galacto-oligosaccharides : technology and engineering aspects
Author: Chockchaisawasdee, Suwimol.
ISNI:       0000 0001 3546 1745
Awarding Body: University of Reading
Current Institution: University of Reading
Date of Award: 2004
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A commercial ~-galactosidase isolated from Kluyveromyces lactis (Maxilact® L2000) was used for the synthesis of galacto-oligosaccharides (GOS) from lactose by trangalatosylation reaction in a stirred-tank reactor. In the experimental range examined (220-400 mg/ml lactose with 2.9-8.7 D/ml enzyme), the results showed the amount of GOS formed depended on lactose concentration. A laboratory scale ultrafiltration membrane reactor was used in a continuous process. Transmembrane pressure played an important role on the flux and productivity due to the impact of concentration polarisation. A probiotic ~-galactosidase, extracted from truncated Bifidobacterium bifidum DSM20215, was used for GOS synthesis in a stirred-tank reactor. The truncated enzyme showed high efficiency in GOS synthesis and gave a high yield (400/0) regardless of initial lactose concentration used (50-150 mg/mllactose). The GOS synthesised by both enzymes were fractionated and analysed for their structures and fermentation properties. The comparison of product structures of GOS synthesised by Maxilact® L2000 in batch and continuous processes showed similarities (1 ~6Galp) but differed from the structures found in the truncated probiotic GOS (1 ~3Galp) and a commercial GOS product (1 ~4Galp). The results from batch culture fermentations showed that all GOS samples increased the number of bifidobacteria and promoted the production of short-chain fatty acids. A model proposed in the literature was applied to estimate kinetic parameters for both enzymes. The model gave a sastisfactory preliminary analysis from which it predicted lactose and GOS concentrations very well. However, improvements are needed to obtain better fits for glucose and galactose concentrations and better sensitivity for the determination of inhibition rate constants.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available