Structure of dried cellular alginate matrix containing fillers provides extra protection for microorganisms against UVC radiation.
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.
Zohar-Perez
C
C
Institute of Biochemistry, Food Science and Nutrition, The Hebrew University of Jerusalem, Faculty of Agricultural, Food and Environmental Quality Sciences, Rehovot 76100, Israel.
Chernin
L
L
Chet
I
I
Nussinovitch
A
A
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
D000464:Alginates; D003470:Culture Media; D006603:Hexuronic Acids; D011837:Radiation-Protective Agents; D020723:Glucuronic Acid