Hydrolysis of milk gangliosides by infant-gut associated bifidobacteria determined by microfluidic chips and high-resolution mass spectrometry.

Gangliosides are receiving considerable attention because they participate in diverse biological processes. Milk gangliosides appear to block pathogen adhesion and modify the intestinal ecology of newborns. However, the interaction of milk gangliosides with gut bifidobacteria has been little investigated. The digestion products of a mixture of gangliosides isolated from milk following incubation with six strains of bifidobacteria were studied using nanoHPLC Chip Q-TOF MS. To understand ganglioside catabolism in vitro, the two major milk gangliosides--GM3 and GD3--remaining in the media after incubation with bifidobacteria were quantified. Individual gangliosides were identified through postprocessing precursor ion scans, and quantitated with the "find by molecular feature" algorithm of MassHunter Qualitative Analysis software. Bifidobacterium infantis and B. bifidum substantially degraded the GM3 and GD3, whereas B. longum subsp. longum and B. animalis subsp. lactis only showed moderate degradation. MALDI FTICR MS analysis enabled a deeper investigation of the degradation and identified ganglioside degradation specifically at the outer portions of the glycan molecules. These results indicate that certain infant gut-associated bifidobacteria have the ability to degrade milk gangliosides releasing sialic acid, and that these glycolipids could play a prebiotic role in the infant gut.