Bifidobacterium longum D2 enhances microbial degradation of long-chain arabinoxylans in an in vitro model of the proximal colon.

Abstract

Long-chain arabinoxylans (LC-AX) are degraded in the colon by intestinal bacteria possessing AX-degrading enzymes, such as bifidobacteria. Enzymatic activity of intestinal bacterial might vary depending on the composition of the gut microbiota. To compare the enzymatic activities of the bacterial gut communities of two healthy individuals (donors D1 and D2), these bacterial communities were inoculated into in vitro model M-SHIME(®). Differences in xylanase activities and denaturing gradient gel electrophoresis profiles, in particular a DNA-band corresponding with Bifidobacterium longum, were found in the proximal colon vessel. 16S rRNA gene sequencing analysis demonstrated the presence of two different B. longum species in these bacterial communities, showing 99% gene sequence similarity with B. longum NCC2705 and B. longum. subsp. longum KACC 91563, respectively, further referred to as B. longum D1 and B. longum D2. When grown on LC-AX as the sole added energy source, B. longum D2 displayed significantly higher activities of β-xylanase (5.3-fold), β-xylosidase (2.9-fold), and α-arabinofuranosidase (1.5-fold), respectively, compared to B. longum D1. When B. longum D2 was inoculated in the M-SHIME, inoculated with the bacterial gut communities of the individual with low AX-degrading enzyme activities, the β-xylanase activity increased (1.5-fold) in the proximal vessel. We demonstrated the presence of differences in LC-AX degrading enzyme activities of the bacterial gut communities of two individuals in the in vitro M-SHIME model, which could be linked to the presence of a potent AX-degrading B. longum (D2) strain.