الفهرس 
Literature ReviewOnly 14 pages are availabe for public view
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Abstract
The present work has targeted the control of Penicillium digitatum, the causative agent of green mold disease of citrus. The management strategy mainly relies on the exploitation of biocontrol agents BCAs. Furthermore, we have prepared polymeric-based nanobiocides conjugated with some safe compounds belonging to GRAS substance. These biocides have been formulated either as an edible film or powder formulations, both were versatile, and they manifest great efficacy in disease incidence and pathogen eradication.
The main findings of the current study can be summarized in the following points:
1. We obtained 15 antagonistic epiphytic bacterial biocontrol agents from the surfaces of healthy orange and lemon fruits. They all together were evaluated for their antagonistic effect against green mold pathogen in the co-culture assay method.
2. The bacterial isolate having the code SH-87 showed the maximum inhibitory effect on the pathogen, it inhibited the radial growth by 67%, compared with the control which showed complete growth covering the whole plate.
3. The macroscopic examination along with the biochemical characterization emphasized that this isolate was Enterobacter.
4. Molecular identification using the molecular technique of 16S r.RNA confirmed the identification, and the strain was identified as Enterobacter sp. SH-87 was recorded in the GenBank with the accession number OP 481922.
5. Enterobacter sp. SH-87 has revealed different mechanisms of its biological activity; it emitted a broad array of volatile organic compounds that exerted a strong antifungal action on mycelial growth.
6. The isolate also produced various diffusible secondary metabolites which were excreted into the broth medium. The CFS has a potent inhibitory effect when it was tested either on radial growth or spore germination of P. digitatum.
7. Regarding the in-vivo application, Enterobacter sp. SH-87 has been investigated as the preventive treatment on artificially infected orange Citrus sinensis. The most active fraction was the fermentation broth FB, so it has been used further in the whole experimental work.
8. In order to boost the activity of the bacterial BCA, a number of GRAS compounds, such as chitosan CHS, salicylic acid SA, and cinnamic acid CA were exploited to make up profound types of formulations.
9. The selected GRAS were active, they significantly affected the growth and development of green mold pathogen either on plates or in planta.
10. These compounds have been formulated with Enterobacter sp. SH-87 FB into edible film formulation for coating of orange, the best concentrations for SA were 4 and 6 mM, CA were 1.5 and 2 mM, and for CHS were 2% (wt./v.).
11. Nanobiocides were radio-chemically prepared based on the use of gamma irradiation that was effectively employed for the degradation of CHS helping decrease its molecular weight from 420 KDa to 24 KDa.
12. The obtained oligo-chitosan fragments mixed with SA and CA were subjected to the synthesis of different nano-formulations either edible film or powder form by lyophilization.
13. The prepared nano-formulations were analyzed with various characterization techniques, such as DLS, zeta potential, FTIR, SEM, and TEM.
14. DLS showed the mean size of the powder nanobioced ranging between 50-100 nm, the zeta potential values emphasize that the prepared formulations have a positive surface charge with higher stability.
15. SEM photographs depicted the surface morphology of the nano-formulations that appeared blowzy and fluffy shaped. On the other hand, the TEM micrographs illustrated the size of the nanostructured to fall between 10-24 nm for all types, with a spherical shape.
16. FTIR spectral analysis demonstrated the appearance of the absorption peaks that are characteristic of CHS and talc powder that was used for preparing the powder nanobiocide.
17. The bioactivity of the nanobiocides was investigated against P. digitatum that infected citrus fruit. Data revealed that the CHSSA 4 mM at 1.5%, CHSSA 6 mM at 0.5%, CHSCA 1.5 mM at 1%, and CHSCA 2 mM at 0.5% were efficient in reducing both LD and DI.
18. A compound treatment of Enterobacter sp. SH-87 with the aforementioned nanobiocides was applied on artificially inoculated orange, results were promising in inhibiting and controlling the disease occurrence.
19. The nanobiocides were used for the preservation and storage of orange at room temperature, storage time was 3 consecutive weeks. Data highlighted the influence of the biocides in delaying the DI compared with control group.