Optimization by Experimental Design of a Galacto-oligosaccharide Production Using Whey Permeate as substrate.

Galacto-oligosaccharides (GOS) are prebiotic molecules with great benefits like ability to resist digestion in the gastrointestinal tract, suppressing the activity of putrefactive bacteria. GOS has a molecular structure that varies in a polymerization degree from two up to ten monosaccharides units, and its prebiotic effect can be found in each one of these structures. The use of whey permeate as a result of ultrafiltration for protein retention has been done together with the use of the enzyme β-galactosidase, and some strategies like experimental designs are used to optimization of the process. This work focuses on the optimization of the galacto-oligosaccharide (GOS) production process, using whey permeate as the raw material, and the commercial beta-galactosidase enzyme of Kluyveromyces lactis. First, a fractional factorial design was developed with 2^5-1 trials and four central points, totalizing 20 assays, evaluating the lactose concentration present on whey permeate (150 g/L to 275 g/L), pH of the reaction medium (6 to 8), enzyme concentration (5 U/g to 20 U/g), process temperature (25°C to 45°C), and rotational speed (150 rpm to 250 rpm) on the responses GOS concentration, production time, yield, and productivity. After selection of the statistically significant variables, a Central Composite Design (CCD) was performed with the variables enzyme concentration and lactose on whey permeate concentration, in a total of 11 assays. Results showed that some variables were not statistically significant in the first trial, like temperature and rotational speed, so being fixed for the second trial. After the CCD, it was possible to achieve optimum results of productivity (about 10 g GOS/L*(U/g)*h), with the construction of a mathematic model and a response surface. This experiment had not influence in the GOS yield, but the enzyme used can be controlled, and this fact can reduce the process cost in an industrial scale.