Simultaneous synthesis and purification (SSP) of galacto-oligosaccharides in batch operation

Abstract

The production of prebiotic galacto-oligosaccharides (GOS) considers the enzymatic synthesis by lactose transgalactosylation and the purification from the reacted mixture (raw GOS). Simultaneous synthesis and purification of GOS (SSP) was conducted in a one-pot operation using β-galactosidase from Aspergillus oryzae and Saccharomyces cerevisiae or Kluyveromyces marxianus cells, allowing the selective removal of unwanted carbohydrates (monosaccharides and lactose). The reaction was carried out in a stirred reactor at 40 °C, pH 4.5 and 200 rpm, using lactose without additional supplements, evaluating the effect of yeast genus (S. cerevisiae or K. marxianus), enzyme-substrate ratio (20–400 IUH/g lactose), initial lactose concentration (20–50% w/w) and substrate mass-biomass ratio (0.05–0.4). The best GOS yield was obtained with S. cerevisiae at 50 IUH/g lactose and 0.25 g cell biomass/g carbohydrates. These conditions were used for scaling-up into a bioreactor (1000 g of 40% w/w lactose) operated under temperature and pH control at an aeration rate of 5 vvm, obtaining a GOS yield of 40% at 24 h of reaction, which is significantly higher than obtained in the conventional system of GOS synthesis. SSP may represent a technological advantage in terms of productivity and yield of GOS production.