Enterococcus faecalis: A Key Metabolic Strain of Myofibrillar Protein-Bound Nε-(Carboxymethyl)lysine In Vitro Simulated Colon after Gastrointestinal Digestion.

Advanced glycation end products (AGEs) are consumed in massive amounts with daily diets, among which high molecular weight protein-bound AGEs, such as Myofibrillar protein-bound Nε-(carboxymethyl)lysine (MP-CML), resist gastrointestinal absorption. This study investigated MP-CML metabolism by human gut microbiota using an in vitro colonic fermentation model. MP-CML digest was separately incubated with faecal suspensions from six volunteers (F1-F3, M1-M3). The F3 sample exhibited the highest activity, reducing CML from 146.54 ± 1.45 μg/mL to 68.62 ± 2.06 μg/mL after 72 h, corresponding to a rate of 53.17%. Then, 17 potential CML-metabolizing bacteria were isolated from the fermentation broth of F3 sample. Surprisingly, strain B1, identified as Enterococcus faecalis, degraded CML at 44.1% when using MP-CML digest as the sole nutrient source. This is the first study showing that E. faecalis can metabolize protein-bound CML, which will provide new insights into the targeted regulation of CML in vivo.