title: Synthesis and characterization of a stable humic-urease complex: application to barley seed encapsulation for improving N uptake.
abstract: BACKGROUND
  Most N fertilizers added to soil are not efficiently used by plants and are lost to the atmosphere or leached from the soil, causing environmental pollution and increasing cost. Barley seed encapsulation in calcium alginate gels containing free or immobilized urease to enhance plant utilization of soil N was investigated.
  
  
  RESULTS
  Urease was immobilized with soil humic acids (HA). A central composite face-centered design was applied to optimize the immobilization process, reaching an immobilization yield of 127%. Soil stability of urease was enhanced after the immobilization. Seed encapsulation with free urease (FU) and humic-urease complex (HUC) resulted in a urease activity retention in the coating layer of 46% and 24%, and in germination rates of 87% and 92%, respectively. Under pot culture conditions, the pots planted with seeds encapsulated with FU and HUC showed higher ammonium N (NH4 (+) -N) (26% and 64%, respectively) than the control soil at 28 days after planting (DAP). Moreover, the seed encapsulation with FU and HUC increased the N uptake 83% and 97%, respectively, at 35 DAP.
  
  
  CONCLUSIONS
  Seed encapsulation with urease could substantially contribute to enhancing plant N nutrition in the early stages of seedling establishment. © 2015 Society of Chemical Industry.
authors.affiliation: Department of Biotechnology and Food Science, Area of Biochemistry and Molecular Biology, University of Burgos, E-09001, Burgos, Spain.
authors.forename: Beaufray G
authors.initials: BG
authors.lastname: Mvila
authors.affiliation: Department of Biotechnology and Food Science, Area of Biochemistry and Molecular Biology, University of Burgos, E-09001, Burgos, Spain.
authors.forename: María C
authors.initials: MC
authors.lastname: Pilar-Izquierdo
authors.affiliation: Department of Biotechnology and Food Science, Area of Biochemistry and Molecular Biology, University of Burgos, E-09001, Burgos, Spain.
authors.forename: María D
authors.initials: MD
authors.lastname: Busto
authors.affiliation: Department of Biotechnology and Food Science, Area of Biochemistry and Molecular Biology, University of Burgos, E-09001, Burgos, Spain.
authors.forename: Manuel
authors.initials: M
authors.lastname: Perez-Mateos
authors.affiliation: Department of Biotechnology and Food Science, Area of Biochemistry and Molecular Biology, University of Burgos, E-09001, Burgos, Spain.
authors.forename: Natividad
authors.initials: N
authors.lastname: Ortega
mesh_terms: D000464:Alginates / Q000737:chemistry; D064751:Ammonium Compounds / Q000032:analysis / Q000378:metabolism; D002118:Calcium / Q000737:chemistry; D032449:Canavalia / Q000201:enzymology*; D000069599:Crop Production / Q000379:methods; D004795:Enzyme Stability; D004800:Enzymes, Immobilized / Q000737:chemistry / Q000378:metabolism*; D005308:Fertilizers; D005427:Flocculation; D005782:Gels; D018525:Germination; D020723:Glucuronic Acid / Q000737:chemistry; D006603:Hexuronic Acids / Q000737:chemistry; D001467:Hordeum / Q000737:chemistry / Q000254:growth & development / Q000378:metabolism*; D006812:Humic Substances; D008958:Models, Molecular; D058458:Nitrogen Cycle; D010940:Plant Proteins / Q000737:chemistry / Q000378:metabolism; D036226:Seedlings / Q000737:chemistry / Q000254:growth & development / Q000378:metabolism; D012639:Seeds / Q000737:chemistry / Q000254:growth & development / Q000378:metabolism*; D013499:Surface Properties; D014510:Urease / Q000737:chemistry / Q000378:metabolism*
chemical_list: D000464:Alginates; D064751:Ammonium Compounds; D004800:Enzymes, Immobilized; D005308:Fertilizers; D005782:Gels; D006603:Hexuronic Acids; D006812:Humic Substances; D010940:Plant Proteins; D020723:Glucuronic Acid; D014510:Urease; D002118:Calcium
keywords: enzyme immobilization; nitrogen availability; plant growth; seed coating; seed encapsulation; soil urease