Effect of acidification or fermentation of barley grain using Limosilactobacillus reuteri or Weissella cibaria on inositol phosphate hydrolysis in vitro

Fermentation of cereal grains may hydrolyse myo-inositol 1,2,3,4,5,6-hexakis (dihydrogen phosphate) (InsP6) and increase concentration of lower order inositol phosphates (InsP) in vitro, thereby increasing nutrient digestibility in diets of swine and poultry. Effects of chemical acidification or fermentation with the lactic acid-producing bacteria Limosilactobacillus reuteri or Weisella cibaria of high β-glucan hull-less barley grain on pH, organic acid concentration, InsP6 hydrolysis and lower order InsP formation were assessed in vitro. In 3 batches, ground barley grain was treated in four forms balanced for water content: 1) unfermented barley (Control); 2) chemically acidified barley with lactic acid and acetic acid (0.019 L/kg barley grain at a ratio of 4:1 (volume/volume)) (ACD); 3) barley fermented with L. reuteri TMW 1.656 (Fermented with L. reuteri); and 4) barley fermented with W. cibaria 10 M FUA3120 (Fermented with W. cibaria). For 24 h in an incubator, ACD and Fermented with L. reuteri were incubated at 37 °C and Fermented with W. cibaria at 30 °C. Barley inositol phosphate6-phosphorus (InsP6-P) was 68%, 64% and 41% lower, respectively, for ACD, Fermented with L. reuteri or Fermented with W. cibaria than Control. Barley grain pH after 24 h, concentration of InsP6-P, inositol phosphate5-phosphorus (InsP5-P), inositol phosphate4-phosphorus (InsP4-P) and sum inositol phosphate6–2-phosphorus (InsP6–2-P) were lower (P < 0.05) for ACD and Fermented barley grain than Control and Fermented with L. reuteri than W. cibaria. Acetate, lactate, inositol phosphate3-phosphorus (InsP3-P) and inositol phosphate2-phosphorus (InsP2-P) concentration was greater (P < 0.05) for ACD and Fermented barley grain than Control. Lactate and InsP2-P concentration were greater (P < 0.01) for Fermented with L. reuteri than W. cibaria. Total P release, cumulative P release of InsP6-P, InsP5-P, InsP4-P and InsP3-P were greater (P < 0.01) for Fermented with L. reuteri than W. cibaria. In conclusion, lower pH in ACD and Fermentation indicated that acidification is important for InsP6 hydrolysis via intrinsic phytase activation in barley grain in vitro. Between strains, fermentation with L. reuteri maximised acidification, lactate concentration and degradation of InsP6-P, InsP5-P, InsP4-P in barley grain.