Microencapsulation of Bacillus velezensis Using Alginate-Gum Polymers Enriched with TiO2 and SiO2 Nanoparticles.

Bacillus bacteria are a group of plant growth stimulants that increase plant growth and resistance to plant pathogens by producing various metabolites. With their large surface area and small size, nanoparticles can be used in controlled-release formulations and increase the efficiency of the desired product. Encapsulation of biological agents in combination with nanoparticles can be an essential step in increasing the performance of these agents in adverse environmental conditions. In this study, which is the result of a collaboration between scientists from Italy and Iran, Bacillus velezensis was encapsulated in alginate combined with whey protein and zedo, mastic, and tragacanth gums in the presence of silica and titania nanoparticles to obtain two-layer and multilayer assemblies acting as novel, smart micro-encapsulation systems. The results of laboratory studies showed that the B. velezensis could produce protease, lipase, siderophore, auxin, and a dissolution of mineral phosphate. Scanning electron microscopy images (SEM) showed that the studied microcapsules were almost spherical. Moisture affinity, swelling, and efficiency of each microcapsule were examined. The results showed that the highest encapsulation efficiency (94.3%) was related to the multilayer formulation of alginate-whey protein-zedo. XRD and FTIR spectroscopy showed that the alginate, whey protein, and zedo were mixed properly and no incompatible composition occurred in the reaction. This study aimed to provide a suitable formulation of biofertilizers based on biodegradable compounds as an alternative to chemical fertilizers, which is low cost and very effective without harming humans and the environment.

Evaluation of Bacillus velezensis for Biological Control of Rhizoctonia solani in Bean by Alginate/Gelatin Encapsulation Supplemented with Nanoparticles.

Plant growth promoting rhizobacteria (PGPR) are a group of bacteria that can increase plant growth; but due to unfavorable environmental conditions, PGPR are biologically unstable and their survival rates in soil are limited. Therefore, the suitable application of PGPR as a plant growth stimulation is one of the significant challenges in agriculture. This study presents an intelligent formulation based on Bacillus velezensis VRU1 encapsulation enriched with nanoparticles that was able to control Rhizoctonia solani on the bean. The spherical structure of the capsule was observed based on the Scanning Electron Microscope image. Results indicated that with increasing gelatin concentration, the swelling ratio and moisture content were increased; and since the highest encapsulation efficiency and bacterial release were observed at a gelatin concentration of 1.5%, this concentration was considered in mixture with alginate for encapsulation. The application of this formulation which is based on encapsulation and nanotechnology appears to be a promising technique to deliver PGPR in soil and is more effective for plants.

Nano-Encapsulation of Plant Growth-Promoting Rhizobacteria and Their Metabolites Using Alginate-Silica Nanoparticles and Carbon Nanotube Improves UCB1 Pistachio Micropropagation.

UCB-1 is the commercial rootstock of pistachio. Reproduction of this rootstock by tissue culture is limited by low levels of proliferation rate. Therefore, any compound that improves the proliferation rate and the quality of the shoots can be used in the process of commercial reproduction of this rootstock. Use of plant growth-promoting bacteria is one of the best ideas. Given the beneficial effects of nanoparticles in enhancement of the growth in plant tissue cultures, the aim of the present study was to investigate the effects of nanoencapsulation of plant growth-promoting rhizobacteria (using silica nanoparticles and carbon nanotubes) and their metabolites in improving UCB1 pistachio micropropagation. The experiment was conducted in a completely randomized design with three replications. Before planting, treatments on the DKW medium were added. The results showed that the use of Pseudomonas fluorescens VUPF5 and Bacillus subtilis VRU1 nanocapsules significantly enhanced the root length and proliferation. The nanoformulation of the VUPF5 metabolite led to the highest root length (6.26 cm) and the largest shoot (3.34 cm). Inoculation of explants with the formulation of the metabolites (both bacterial strains) significantly elevated the average shoot length and the fresh weight of plant compared to the control. The explants were dried completely using both bacterial strains directly and with capsule coating after the three days.

Investigating the formulation of alginate- gelatin encapsulated Pseudomonas fluorescens (VUPF5 and T17-4 strains) for controlling Fusarium solani on potato.

Nanotechnology is one of the most fascinating sciences with a great potential to improve many agricultural products. Use of nanoparticles in plant disease management is a novel area which may prove very effective in future. Use of nanomaterials and biocompatible compounds in nano-encapsulation of antagonist bacteria is an important step in enhancing the efficiency of these agents in adverse environmental conditions. Two strains of Pseudomonas fluorescens (VUPF5 and T17-4) were used for alginate-gelatin nanocomposite beads with different concentrations of gelatin. The moisture content, swelling, and releasing of encapsulated viable bacteria was investigated in vitro and in vivo conditions. The results of FT-IR and X-ray diffraction analysis revealed that when gelatin was added into sodium alginate, electrostatic interaction occurred. The swelling and moisture content of nanocomposite beads grew with gelatin enhancement. The maximum encapsulation efficiency at the gelatin concentration of 1.5% in VUPF5 and T17-4 was 91.23% and 87.23%, respectively. Further, the greenhouse experiment showed that inoculation of potato with bacterial strains and nanocomposite beads of these strains reduced disease incidence. The encapsulation method described in this study can be effectively used to protect the plant probiotic bacteria inoculum from harmful conditions of the soil for its successful establishment in the rhizosphere.