Optimization of arabitol production by karyoductant SP-K 7 of S. cerevisiae V30 and P. stipitis CCY 39501 using response surface methodology.

L-arabitol is used in the food and pharmaceutical industries. It can be secreted by genetically modified Saccharomyces cerevisiae carrying the genes responsible for pentose metabolism in yeast cells. The process of the biotransformation of L-arabinose to arabitol is highly dependent on culture conditions. The aim of this investigation was to use statistical response surface methodology (RSM) for optimization of biotransformation of L-arabinose to arabitol by a karyoductant of S. cerevisiae V30 and Pichia stipitis CCY 39501, named SP-K7. Batch cultures of yeast were performed according to a Plackett-Burman design, and three factors, rotation speed, L-arabinose concentration, and temperature, were chosen for a central composite design (CCD) applied in order to optimize the production of the polyol by the karyoductant. On the basis of results obtained using 20 combinations of batch cultures of karyoductant SP-K7, the optimal levels of the factors were determined as: rotation speed 150 rpm, concentration of L-arabinose 32.5 g/l, and temperature 28 degrees C. In such conditions, the predicted concentration of arabitol after two days of incubation of SP-K7 should be 18.367 g/l. The value of R2 = 0.93195 suggested that this model was well-fitted to the experimental data. A verification of the model in experimental conditions confirmed its usefulness.