Tailored enzymatic production of oligosaccharides from sugar beet pectin and evidence of differential effects of a single DP chain length difference on human faecal microbiota composition after in vitro fermentation

Sugar beet pectin was degraded enzymatically and separated by ion exchange chromatography into series of highly purified homogalacturonides and rhamnogalacturonides. MALDI-TOF/TOF mass-spectrometry was used to determine sizes and structural features. The methodology was based on the sequential use of monocomponent enzymes that were selected to target specific substructures in the sugar beet pectin.

Notably pectin lyase and rhamnogalacturonan I lyase were used, which allowed detection of the resulting cleavage products by UV spectroscopy. Seven different homogalacturonides (HG) with degrees of polymerization (DP) from 2 to 8 and six different rhamnogalacturonide (RGI) structures, ranging from DP4 to 6 with defined galactose substitutions were purified.

Total recoveries of 200 mg homogalacturonides and 67 mg rhamnogalacturonides per gram sugar beet pectin were obtained. This integrated biorefining method provides an option for advanced upgrading of sugar beet pectin into HG and RGI oligosaccharides of defined size and structure. In vitro microbial fermentation by human faecal samples (n = 9) showed a different response to the DP4 and DP5 HG structures on the ratio between Bacteroidetes and Firmicutes.

This indicates that pectic oligosaccharides with only slightly different structures have significantly different biological effects. This is the first report of pectic oligosaccharide activity on gut bacterial populations related to the metabolic syndrome associated with obesity.