Galacto-oligosaccharide production by Lactobacillus delbrueckii ssp. bulgaricus whole cells and lysates

Authors: Guron, Giselle; Hotchkiss, Arland; Renye, John; Oest, Adam; McAnulty, Michael

Submitted to: Journal of Dairy Science Communications
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/18/2024
Publication Date: 6/13/2024
Citation: Guron, G.P., Hotchkiss, A.T., Renye Jr, J.A., Oest, A.M., McAnulty, M.J. 2024. Galacto-oligosaccharide production by Lactobacillus delbrueckii ssp. bulgaricus whole cells and lysates. Journal of Dairy Science Communications. https://doi.org/10.3168/jdsc.2024-0580.
DOI: https://doi.org/10.3168/jdsc.2024-0580

Interpretive Summary: Consumers interested in gastrointestinal health aim to increase their uptake of prebiotics in their diets to help regulate their microbiomes because they promote the growth of beneficial bacteria like Bifidobacterium sp. In this study, two strains of bacteria named Lactobacillus delbrueckii subsp. bulgaricus, which are normally used for producing yogurt, have the additional ability to produce prebiotics from milk sugar called galacto-oligosaccharides. These bacteria require no genetic modification and the enzyme responsible is extracted simply by mechanical lysis without additional chemicals. These bacteria are generally regarded as safe, so these bacteria would be ideal for the production of these prebiotics.

Technical Abstract: ß-galactosidase is currently applied in foods for its hydrolysis activity to reduce lactose but can also be utilized for its transgalactosylation activity to synthesize galacto-oligosaccharides (GOS) as prebiotics. The ability of GRAS-status Lactobacillaceae strains to exhibit such activities would benefit consumers for either purpose. The objective of this study was to screen whole cells and their lysates to identify strains synthesizing the highest amount of GOS in the presence of differing lactose concentrations. Compared to eleven other strains, Lactobacillus delbrueckii subsp. lactis LDL20 and L. delbrueckii subsp. bulgaricus YB1 hydrolyzed ortho-Nitrophenyl-ß-galactoside the most, but only L. bulgaricus LB11 and YB1 whole cells reduced lactose, even in comparison to their lysates. LB11, YB1, and L. bulgaricus B548 lysates produced the most GOS with 300 g/L lactose at 50 °C for 18 h compared to the other strains and cell preparations based on HPAEC-PAD analysis. LB11 released the highest glucose to galactose ratio among all the strains (2.79 ± 0.55 g per g galactose). The LB11 lysate produced the most glucose, 38.8 ± 5.5 g/L and 37.3 ± 1.4 g/L with 300 g/L or 150 g/L lactose, respectively, while the YB1 lysate produced 34.0 ± 2.6 g/L and 29.8 ± 1.1 g/L glucose with 300 or 150 g/L lactose, respectively. The amounts of galactose and glucose released correlated with the production of GOS based on HPAEC-PAD analysis. L. bulgaricus LB11 and YB1 whole cells have potential to be added to milk products to synthesize GOS while reducing the lactose in solution, but optimal GOS production requires cell lysates.