Galacto-oligosaccharide Production by Ssp. Whole Cells and Lysates

β-Galactosidase is currently applied in foods for reduction of lactose but can also be used for its transgalactosylation activity to synthesize galacto-oligosaccharides (GOS) as prebiotics. The ability of GRAS-status strains to exhibit such activities would benefit consumers given their extensive history with dairy products. The objective of this study was to characterize the production of GOS in 6 strains for their ability to synthesize GOS in 50 m sodium phosphate (pH 6.5) with a high lactose concentration of 788.8 m at 50°C. ssp. B548, LB11, and YB1 lysates released the most glucose at 112.8 ± 6.2 m, 150.4 ± 11.7 m, and 190.2 ± 12.2 m, respectively. However, the ratio of free glucose to galactose released by B548 lysate (1.4 ± 0.3) was lower than that of LB11 (2.8 ± 0.6) and YB1 (2.5 ± 0.6) lysates, so the latter strains were screened at different initial lactose concentrations. The GOS yield from YB1 was not dependent on initial lactose concentration, averaging 54.3 ± 0.6% across starting lactose concentrations. However, optimal LB11 transgalatosylation had an initial concentration of 394.4 m lactose instead of 788.8 m, resulting in a GOS yield of 56.8% instead of 47.3%. In all cases for LB11, the lysates had greater free glucose, galactose, and GOS yield than whole cells. The ability of 2 ssp. strains to produce GOS from common lactose-containing ingredients can have a range of applications in the dairy industry.