Sequential optimization approach for prebiotic galactooligosaccharides synthesis by Pseudozyma tsukubaensis and Pichia kluyveri

- Galactooligosaccharides (GOS) was produced by P. tsukubaensis and P. kluyveri.
- A sequential strategy of two experimental designs was used to optimize GOS yield.
- Plackett-Burman design enabled to define the effect process variables on GOS yield.
- Response surface methodology was useful to optimize distinct variables collectively.
- Optimized process is interesting for GOS production and lactose hydrolysis.

Synthesis of the prebiotic galactooligosaccharides from lactose fermentation by Pseudozyma tsukubaensis and Pichia kluyveri was investigated. In this study, a sequential strategy of two experimental designs was used to optimize galactooligosaccharides production. First, Plackett-Burman screening design was applied to evaluate the effects of lactose, yeast extract, urea concentration, inoculum concentration, pH and agitation rate on the response of galactooligosaccharides yield synthesized by both yeasts. The preliminary Plackett-Burman design allowed the identification of the pH and urea concentration as statistically significant variables in the range studied. In order to find the optimal conditions for galactooligosaccharides synthesis, a central composite rotational design was employed. The independent variables were lactose, yeast extract and urea concentrations, and the response taken into account was galactooligosaccharides yield produced by P. tsukubaensis. The optimized condition for this prebiotic synthesis was: lactose, yeast extract and urea at concentrations of 26.0, 0.8 and 1.8 g/100 mL, respectively. Under the optimized and validated conditions, the transgalactosylation activity of P. tsukubaensis resulted in GOS yield of 28.35 GOS (g)/100 g of lactose at 24 h, with a maximum GOS production of 73.71 g/L, and approximately 50 g/100 g of lactose hydrolysis.