title: Degradation of phytate by high-phytase Saccharomyces cerevisiae strains during simulated gastrointestinal digestion.
abstract: Hydrolysis of extracellular phytate (InsP(6)) by high-phytase yeast strains and survival of yeast cells were studied at simulated digestive conditions using yeast peptone dextrose growth medium and wheat gruel as model meals. An in vitro digestion method was modified to better correlate with the gastric pH gradient following food intake in vivo. High-phytase yeast gave a strong reduction of InsP(6) (up to 60%) in the early gastric phase, as compared to no degradation by wild-type strains. The degree of InsP(6) degradation during digestion was influenced by the type of yeast strain, cell density, and InsP(6) concentration. Despite high InsP(6) solubility, high resistance against proteolysis by pepsin, and high cell survival, degradation in the late gastric and early intestinal phases was insignificant. Dependency on pH for phytase expression and/or activity seemed thus to be an important limiting factor. Although further studies are needed, our results show the potential of using yeast as a phytase carrier in the gastrointestinal tract.
authors.affiliation: Department of Chemical and Biological Engineering-Food Science, Chalmers University of Technology, Göteborg, Sweden.
authors.forename: Ann-Katrin
authors.initials: AK
authors.lastname: Haraldsson
authors.forename: Jenny
authors.initials: J
authors.lastname: Veide
authors.forename: Thomas
authors.initials: T
authors.lastname: Andlid
authors.forename: Marie Larsson
authors.initials: ML
authors.lastname: Alminger
authors.forename: Ann-Sofie
authors.initials: AS
authors.lastname: Sandberg
mesh_terms: D010832:6-Phytase / Q000378:metabolism*; D004063:Digestion; D041981:Gastrointestinal Tract / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D008954:Models, Biological; D010833:Phytic Acid / Q000378:metabolism*; D015203:Reproducibility of Results; D012441:Saccharomyces cerevisiae / Q000201:enzymology*; D012995:Solubility
chemical_list: D010833:Phytic Acid; D010832:6-Phytase