Peanut, tree nuts and sesame seeds support Bifidobacterial growth and metabolism: E. Shannon1; S. Kim1; L. Yao1; C. Ndwandwe1; C. Stanton2, 1; F. Koc2; C. Venter3; J. Hourihane4; D. Van Sinderen1; L. O'Mahony1. (1) APC Microbiome Ireland, Cork, Ireland; (2) Teagasc Food Research Centre, Moorepark, Fermoy, Cork, Ireland; (3) University of Colorado, Children's Hospital Colorado, Aurora, Colorado City, United States of America; (4) Royal College of Surgeons in Ireland (RCSI), 123 Saint Stephen's Green, Dublin 2, Ireland

The gut microbiome plays an essential role in early life immune development and prevention of food allergy. In particular, bifidobacteria induce immunoregulatory networks. Lower levels of bifidobacteria have been associated with increased risk of food allergy and atopic dermatitis. It is not clear why allergic infants have lower levels of bifidobacteria, but dietary factors are likely to play a key role. We previously showed in our CORAL infant cohort studies that consumption of peanut, tree nuts and sesame during weaning was associated with higher levels of bifidobacteria. The aim of this study was to determine whether peanut, walnut, pecan, pistachios, and sesame can directly modify the growth and metabolism of infant bifidobacterial strains. Ten infant Bifidobacterium strains were cultured anaerobically with in vitro digested raw nuts and minimal media for 48 hours. Growth was measured by pH, optical density at 600 nm, and colony forming units. Short chain fatty acid (SCFA) metabolites were quantified by high performance liquid chromatography. Immunomodulatory function of bifidobacterial metabolites were measured using human aryl hydrocarbon receptor (AhR) reporter HT-29 cell line and peripheral blood mononuclear cells (PBMCs). While all tested Bifidobacterium strains showed some in vitro growth on the test substrates, two strains were found to be most capable of metabolising peanut, walnut, pecan, pistachios, and sesame substrates, namely, Bifidobacterium longum subsp. longum and Bifidobacterium pseudocatenulatum. B. longum subsp. longum grew most abundantly on peanut, followed by walnut, sesame, pecan, and pistachio. B. pseudocatenulatum grew most abundantly on walnut followed by sesame, pistachio, peanut, and pecan. Both strains produced SCFA upon in vitro fermentation of nuts. Acetate was the most prevalent SCFA, with lower levels of propionate, isobutyrate, butyrate, isovalerate, and valerate. In addition, B. longum subsp. longum and B. pseudocatenulatum secreted metabolites that activated the AhR in HT-29 reporter cells. Bifidobacteria are capable of utilising peanut, walnut, pecan, pistachios, and sesame for growth and immunoregulatory metabolite production, which opens the possibility of targeted dietary intervention during weaning to improve the early-life microbiome. The early introduction of potentially allergenic plants foods such as peanut and tree nuts protect against food allergy development. Our study suggests that these foods are utilised by the early life microbiota, which may play a role in their allergy protective effects complementing mechanisms associated with direct sampling by the immune system.