title: Expression of bifidobacterial phytases in Lactobacillus casei and their application in a food model of whole-grain sourdough bread.
abstract: Phytases are enzymes capable of sequentially dephosphorylating phytic acid to products of lower chelating capacity and higher solubility, abolishing its inhibitory effect on intestinal mineral absorption. Genetic constructions were made for expressing two phytases from bifidobacteria in Lactobacillus casei under the control of a nisin-inducible promoter. L. casei was able of producing, exporting and anchoring to the cell wall the phytase of Bifidobacterium pseudocatenulatum. The phytase from Bifidobacterium longum spp. infantis was also produced, although at low levels. L. casei expressing any of these phytases completely degraded phytic acid (2mM) to lower myo-inositol phosphates when grown in MRS medium. Owing to the general absence of phytase activity in lactobacilli and to the high phytate content of whole grains, the constructed L. casei strains were applied as starter in a bread making process using whole-grain flour. L. casei developed in sourdoughs by fermenting the existing carbohydrates giving place to an acidification. In this food model system the contribution of L. casei strains expressing phytases to phytate hydrolysis was low, and the phytate degradation was mainly produced by activation of the cereal endogenous phytase as a consequence of the drop in pH. This work shows the capacity of lactobacilli to be modified in order to produce enzymes with relevance in food technology processes. The ability of these strains in reducing the phytate content in fermented food products must be evaluated in further models.
authors.affiliation: Lactic Acid Bacteria and Probiotics Laboratory, Institute of Agrochemistry and Food Technology (IATA-CSIC), Av. Agustín Escardino 7, 46980 Paterna, Valencia, Spain; Cereal Group, Institute of Agrochemistry and Food Technology (IATA-CSIC), Av. Agustín Escardino 7, 46980 Paterna, Valencia, Spain.
authors.forename: Izaskun
authors.initials: I
authors.lastname: García-Mantrana
authors.affiliation: Lactic Acid Bacteria and Probiotics Laboratory, Institute of Agrochemistry and Food Technology (IATA-CSIC), Av. Agustín Escardino 7, 46980 Paterna, Valencia, Spain.
authors.forename: María J
authors.initials: MJ
authors.lastname: Yebra
authors.affiliation: Cereal Group, Institute of Agrochemistry and Food Technology (IATA-CSIC), Av. Agustín Escardino 7, 46980 Paterna, Valencia, Spain.
authors.forename: Monika
authors.initials: M
authors.lastname: Haros
authors.affiliation: Lactic Acid Bacteria and Probiotics Laboratory, Institute of Agrochemistry and Food Technology (IATA-CSIC), Av. Agustín Escardino 7, 46980 Paterna, Valencia, Spain. Electronic address: btcmon@iata.csic.es.
authors.forename: Vicente
authors.initials: V
authors.lastname: Monedero
mesh_terms: D010832:6-Phytase / Q000235:genetics* / Q000378:metabolism; D001644:Bifidobacterium / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*; D001939:Bread / Q000382:microbiology*; D050260:Carbohydrate Metabolism / Q000235:genetics; D002523:Edible Grain / Q000378:metabolism; D005285:Fermentation; D005433:Flour / Q000032:analysis; D005511:Food Handling; D005524:Food Technology / Q000379:methods; D006868:Hydrolysis; D007780:Lacticaseibacillus casei / Q000235:genetics / Q000378:metabolism*; D010833:Phytic Acid / Q000378:metabolism*
chemical_list: D010833:Phytic Acid; D010832:6-Phytase
keywords: Bifidobacterium; Lactobacillus casei; Phytase; Phytate; Phytic acid or myo-inositol hexakisphosphate (PubChem CID: 890); Sourdough; Whole wheat