(17d) Evaluation of Microwave Irradiation Effect on Reaction, Separation (ATPS) and Simultaneous Reaction-Separation of Galactooligosaccharides (GOS) Production

GOS are carbohydrates with a glucose molecule linked to 2-5 molecules of galactose. GOS are prebiotics and are industrially obtained by enzymatic reactions. Source of GOS reaction might be lactose or cheese whey, with a lactose content higher than 70%. Hydrolysis reaction breaks lactose into glucose and galactose, which reacts to form GOS, through transgalactosylation reaction; presence of these monosaccharides inhibit the latest reaction and decrease the GOS production.

ATPS could be used to separate a mixture of substances according to its preferential affinity to one of the two phases in this system, it is formed by two polymers or a salt and a polymer dissolved in water upon a specific concentration to produce phase separation. There are many factors affecting this operation like pH, temperature, polymer, salt and substances concentration, molecular weight of polymer and polymer / salt ratio, ATPS could be used to separate inhibitor monosaccharides, from GOS mixture.

Microwave irradiation has shown a positive effect on ATPS separation and has been used as reaction media to produce GOS from lactose.

ATPS was used in this work to produce and separate galactooligosaccharides simultaneously. Reaction medium is formed of lactose at different concentrations, polyethyleneglycol (PEG) and sodium citrate to form ATPS, pH of 4.5 – 5.5, temperatures tested were between 40 - 60°C. Was evaluated the effect of microwave irradiation on reaction, ATPS separation and simultaneous reactions-separation conditions.

Were stablished all conditions in ATPS that produced optimized results, which were expressed as partition coefficient, separation yield, selectivity to GOS and reaction yield. Selectivity to GOS raise up more than 40%, relative to conventional medium, reaction yield did not change statistically. Separation of carbohydrates mixture is according to its molecular weight, heaviest substances (GOS) kept mainly in the bottom phase (sodium citrate), while monosaccharides kept in top phase (PEG) mainly. Optimized results of reaction, separation and simultaneous reaction-separation were tested into microwave irradiation. Yield and productivity were increased with microwave action.