title: Structure of dried cellular alginate matrix containing fillers provides extra protection for microorganisms against UVC radiation.
abstract: Soil microorganisms in general and biocontrol agents in particular are very sensitive to UV light. The packaging of biocontrol microorganisms into cellular solids has been developed as a means of reducing loss caused by exposure to environmental UV radiation. The bacterial and fungal biocontrol agents Pantoea agglomerans and Trichoderma harzianum were immobilized in freeze-dried alginate beads containing fillers and subjected to 254 nm UV radiation (UVC). Immobilization of cells in freeze-dried alginate-glycerol beads resulted in greater survival after UV irradiation than for a free cell suspension. Adding chitin, bentonite or kaolin as fillers to the alginate-glycerol formulation significantly increased bacterial survival. Immobilization in alginate-glycerol-kaolin beads resulted in the highest levels of survival. The transmissive properties of the dried hydrocolloid cellular solid had a major influence on the amount of protection by the cell carrier. Dried alginate matrix (control) transmitted an average of 7.2% of the radiation. Filler incorporation into the matrix significantly reduced UV transmission: Alginate with kaolin, bentonite and chitin transmitted an average of 0.15, 0.38 and 3.4% of the radiation, respectively. In addition, the filler inclusion had a considerable effect on the bead's average wall thickness, resulting in a approximately 1.5- to threefold increase relative to beads based solely on alginate. These results suggest that the degree of protection of entrapped microorganisms against UVC radiation is determined by the UV-transmission properties of the dried matrix and the cellular solid's structure. It is concluded that for maximum protection against UV-radiation-induced cell loss, biocontrol microorganisms should be immobilized in alginate-glycerol beads containing kaolin.
authors.affiliation: Institute of Biochemistry, Food Science and Nutrition, The Hebrew University of Jerusalem, Faculty of Agricultural, Food and Environmental Quality Sciences, Rehovot 76100, Israel.
authors.forename: C
authors.initials: C
authors.lastname: Zohar-Perez
authors.forename: L
authors.initials: L
authors.lastname: Chernin
authors.forename: I
authors.initials: I
authors.lastname: Chet
authors.forename: A
authors.initials: A
authors.lastname: Nussinovitch
mesh_terms: D000464:Alginates / Q000528:radiation effects*; D018914:Cells, Immobilized / Q000528:radiation effects; D015169:Colony Count, Microbial / Q000379:methods; D003470:Culture Media / Q000528:radiation effects; D004307:Dose-Response Relationship, Radiation; D005612:Freeze Drying / Q000379:methods; D020723:Glucuronic Acid; D006603:Hexuronic Acids; D008863:Microspheres; D020636:Pantoea / Q000166:cytology / Q000254:growth & development / Q000528:radiation effects*; D011829:Radiation Dosage; D011837:Radiation-Protective Agents / Q000528:radiation effects*; D013172:Spores, Fungal / Q000166:cytology / Q000254:growth & development / Q000528:radiation effects; D014242:Trichoderma / Q000166:cytology / Q000254:growth & development / Q000528:radiation effects*; D014466:Ultraviolet Rays
chemical_list: D000464:Alginates; D003470:Culture Media; D006603:Hexuronic Acids; D011837:Radiation-Protective Agents; D020723:Glucuronic Acid