Synthesis of galactooligosaccharides using Kl. marxianus and Streptococcus thermophilus

The purpose of the study was to investigate the effect of lactose concentration and fermentation time on the synthesis of galacto-oligosaccharides (GOS) using autolysate of yeast Kluyveromyces marxianus and lactic acid microorganisms Streptococcus thermophilus to determine the optimal technological parameters of the process. Each experiment involved three stages. The first stage - cultivation of yeast -was carried out in a reconstituted to mass fraction of solids 15 % in cheese whey for 13±1 hours at temperature of 30±2 °C. The second stage - autolysis of microorganism cells for enzyme extraction - was carried out at temperature of 52±2 °С for 24 hours. A feature of the process was the addition of 5 % activated starter culture Str. thermophilus before the autolysis of yeast. The third stage, the purpose of which was the synthesis of GOS, was carried out for 24 hours at temperature of 52 °C after the addition of lactose to the autolysate to a concentration of lactose of 20, 25 and 30 %. The content of GOS in fermented whey was determined by HPLC on LC-20 Prominence chromatograph (SHIMADZU, Japan). It is established that the dependence of the yield of GOS on the concentration of lactose is nonlinear. The highest concentration of GOS was obtained in 25 % solutions of milk sugar after fermentation for 12 hours. It is shown that the first fermentation period is unstable in the formation of GOS, dispersion of data is 22-27 % in 5 hours and 16-17 % in 8 hours. In the future, the process becomes more predictable, after 10-12 hours and after 24 hours of fermentation, the relative error in measuring the concentration of GOS decreases to 5-10 %. Optimization of the process allowed to determine the fermentation time (14,6 hours) and lactose concentration (26, 36 %), at which the maximum yield of GOS (36-45%) can be obtained. The results of the research became the basis for the development of the method for preparing a food supplement for functional nutrition with an increased content of GOS and a low cost, which has been patented.

Kluyveromyces marxianus, Streptococcus thermophilus, galactooligosaccharides, synthesis, Kluyveromyces marxianus, Streptococcus thermophilus