44E-11 |
Description of a selective biocatalyst for preparation of galacto-oligosaccharides |
C. OTERO, Institute of Catalysis, Consejo Superior de Investigaciones Científicas, Campus Universitario, Cantoblanco, Madrid, 28049, Spain, M. I. Del-Val, C. G. Hill, Jr., Dept. of Chemical Engineering, Univ. of Wisconsin, Madison, and A. Llorente, I+D Department, Productos Aditivos S.A., Spain. Galacto-oligosaccharides comprised of 3-10 molecules of galactose and glucose have attracted significant industrial attention because of their potential for use in the formulation of value-added food products. Their ability to promote the growth of Bifidobacterium spp. in the large intestine is beneficial to human health. Galacto-oligosaccharides can be obtained from lactose by employing the transferase activity of different glycosidases. The present study describes the ability of a commercial liquid enzyme preparation (Pectinex Ultra-SP) containing endo-polygalacturonase, endo-pectinlyase, pectin esterase and endo-Cx-cellulase activities to accomplish the production of trisaccharides from lactose. Enzymatic reactions were performed in water in individual stoppered glass bottles incubated in an orbital shaker at 200 rpm. All carbohydrate mixtures were analyzed by HPLC using a Kromasil amino column (250 x 4.6 mm). Methyl a-D-glucopyranoside was used as an internal standard in these analyses. The quantity of lactose remaining and the yield of trisaccharide are expressed as percent by weight of the total quantity of carbohydrate in the reaction mixture. However, the selectivity of the reaction is based on the quantity of lactose that reacts. The structural analysis of the product was carried out by mass spectrometry and 1H-NMR, COSY and HSQC spectra using a Bruker DRX-500 MHz spectrometer. Pectinex Ultra-SP. produces a trisaccharide of molecular mass 504. The maximum levels of trisaccharide obtained (18-19% w/w) are similar to those reported for mesophilic enzymes. In terms of its ability to convert lactose to the desired product, Pectinex Ultra-SP has a higher selectivity than mesophilic enzymes for formation of the trisaccharide (62% versus 32 %). Only b-galactosidase from Bacillus circulans has similar selectivity. Although higher conversions of lactose can be obtained with thermophilic enzymes, the selectivity of these reactions towards the trisaccharide is significantly better when Pectinex Ultra-SP is employed (62% versus 31- 43% for thermophilic enzymes).
Session 44E, Nutraceuticals & Functional Foods
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