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Production of Galacto-Oligosaccharides from Whey Lactose by Immobilized Enzyme -Galactosidase from Aspergillus Oryzae and Bacillus Circulans with Chromatographic Separation

Juan Ignacio Sanz Valero, Chemical and Biomolecular Engineering, The Ohio State University, 140 W. 19th Ave, Columbus, OH 43210 and Shang-Tian Yang, Chemical and Biomolecular Engineering Department, The Ohio State University, 140 w. 19th Ave, Columbus, OH 43210.

In this project we developed a production process of galacto-oligosaccharides (GOS) and posterior chromatographic separation for separating and purifying GOS. GOS, also known as Bifidus growth factor, are produced from whey permeate or lactose. Although many uses have been found for whey and lactose, including uses in infant formula, bakery, dairy and confectionary products, currently less than 50% of the whey permeate and lactose produced in the US is used in salable products. Also, its market price is not stable, fluctuating between $0.12 and $0.40 per lb. The surplus of whey must be treated as a pollutant because of its high biological oxygen demand (BOD) value. Therefore, the conversion of whey lactose into a highly valuable product such as GOS (more than $5/lb) is of high interest to the food industry. GOS and other non-digestible oligosaccharides are known to have many beneficial health effects, and are expected to have wide applications as prebiotic food ingredients and dietary supplements.

The process for GOS production from whey lactose involves two sequential immobilized enzyme reactors and a chromatographic separation process for purification of GOS. Lactases, -glycosidase enzymes, from Aspergillus oryzae(mold) and Bacillus circulans (bacterium) were used to convert lactose to GOS by a transgalactosylation reaction. Products containing 28% of GOS (at 50% conversion) and 40% of GOS (at 60% lactose conversion) were obtained using lactase from A. oryzae and B. circulans, respectively. Two sequential plug-flow reactors with the immobilized -galactosidases were used to convert lactose (400g/L) to GOS with a high productivity of 200 g/L/h, which is about 100-fold higher than most other processes. To further increase the GOS content in the final product, a simulated moving bed (SMB) chromatographic technique was studied to separate GOS from lactose and monosaccharides. SMB offers a high efficiency due to the continuous operation and efficient use of the mobile and stationary phases, allowing high sample loading with improved productivity and saving 90% in solvent consumption as compared with conventional liquid chromatography methods. The chromatographic separation process was optimized in several parameters: a) the amount of cross linking in the stationary phase, b) the choice of counter ion, c) the effect of temperature, e) the particle size of the resin beads, and e) the effect of flow rate.