| In view of the serious diseases of seedling in Xinjiang, the microbial inoculums were employed to prevent the diseases and promote the growth or conduct the seed coating application. However, the presence of short survival time and poor stability limit the application of biological seed coating agent. In this study, microcapsules formulation encapsulating functional strains were developed based on the concept of encapsulated microbial suspension seed coating agent. Microbial microcapsules based on Baillus subtilis SL-13 were synthesized via emulsification/internal gelation. The optimum varying composition proportions on ESCA were obtained through the screen of SCA and the optimization of varying composition proportions. The pot experiments were employed to evaluate the disease prevention and growth-promoting of the ESCA. The main research work and experimental results are as follows:(1) Bacillus subtilis SL-13 was used as wall cores, microcapsules were prepared by the endogenous emulsion method. And the three parameters ratio of bacteria to glue, concentration of sodium alginate, concentration of calcium carbonate on the influence of microcapsule were discussed. Then the water content of microcapsules, inflation performance and embedding rate were studied. The optimum conditions in preparation of microcapsules were as follows: sodium alginate concentration was 2%, the bacteria glue ratio of 1:3, the concentration of calcium carbonate was 2.5%.(2) The microcapsule particle size distribution in the micron range, and microparticles nearly spherical shape and have a good dispersion, when adding the gelatin in the wall material,. At 0% gelatin, the average particle diameter was 255.1 μm, and an average particle size of 400.8 μm was obtained at 2.5% gelatin concentration. Particle size, swelling and biodegradation of beads were increased with gelatin content increase. The maximum encapsulation efficiency was 93.44% at a gelatin concentration of 1.5%. Furthermore, the viability of encapsulated SL-13 could be preserved at more than 108 CFU/m L, whereas the viability rate of SL-13 in the beads was maintained at about 70%. This encapsulation strategy could be considered as a potential alternative to future applications in the agricultural industry.(3) After screening of fertilizer, the best film formers was sodium alginate and polyvinyl alcohol compound, the best thickener was gum Arabic, the best dispersant was sodium dodecyl sulfate, and the best antifreeze was ethylene glycol. The film former were determined by orthogonal experiment of additive in seed coating. And 1.0% sodium alginate, 4.0% polyvinyl alcohol,0.5% packing bentonite, and the optimum concentration of gum Arabic of thickener was 0.3%, the optimum concentration of sodium dodecyl sulfate of dispersant was 3.0%. The preparation of microcapsule suspension had best performance, indicated evenly on the surface of thin film, no bubble, and easy to peel, uniformity of more than 90%, and the loss rate was less than 1%. The embedding number of bacteria was the largest, amount to 6.42×106 cfu/seeds, which beneficial to seed germination and seedling growth.(4) Pot experiments results indicated that the germination rate of cotton seeds increased treated with ESCA4, and the growth factors of the cotton seedlings, such as plant height, root length, whole plant fresh weight, and whole plant dry weight increased by 52.70%, 25.13%, 46.47%, and 33.21%, respectively. Further analysis demonstrated that the peroxidase and superoxide dismutase activities of cotton seedlings improved, whereas their malondialdehyde contents decreased. Therefore, the ESCA can efficiently improve seed germination and biomass.The novel encapsulated microbial suspension seed coating agent would promote the seed germination and the seedling growth, and control the seedling diseases. Hence, the encapsulated microbial suspension seed coating agent will be widely applied in agriculture. |
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