Enterococcus faecalis CIRM-BIA2928 induces gluten proteolysis and reduces gluten immunoreactivity during fermentation

Wheat is a staple food for human consumption thanks to its nutritional and technological quality. Worldwide, around 8% of the population is affected by wheat-related disorders, such as wheat allergy, celiac disease or non-celiac gluten-sensitivity. Food processing can modify gluten protein structure and immunoreactivity. Bacterial fermentation by Lactic Acid Bacteria (LAB) is of particular interest, as fermentation can cause the hydrolysis of gluten proteins. Our study aimed to identify LAB capable of hydrolysing gluten and to establish optimal fermentation conditions. Fifteen bacterial strains were screened on a liquid medium containing gluten as the sole nitrogen source. The protein profile of all fermentation products was characterised by SDS-PAGE. Of selected strains, a detailed peptide analysis of hydrolysed fermentation products was performed using mass spectrometry. Protein immunoreactivity was assessed by competitive ELISA. Finally, the bacterial enzyme class responsible for gluten hydrolysis was identified. One strain of Enterococcus faecalis (CIRM-BIA2928) was capable of hydrolysing gluten during fermentation. Fermentation time and bacterial cell concentration were identified as two factors modulating proteolysis. Gluten proteolysis led to a clear reduction in the immunoreactivity of the R5 peptide, implicated in celiac disease. This proteolysis was caused by zinc metalloprotease enzymes. Enterococcus faecalis CIRM-BIA2928 has interesting characteristics for hydrolysing wheat proteins. Hydrolyzed gluten could be used for preventive purposes to induce oral tolerance or for therapeutic purposes in wheat-allergic patients to avoid triggering a reaction.