Nano-Bioformulations of Plant Growth Promoting Rhizobacteria

Project no. 28513 · Status: Kapanmış (Yayın bekleniyor) · 2023

Summary

Many Bacillus species identified as PGPRs can develop tolerance to heavy metals in nature and survive for long periods of time, improving soil quality and promoting plant growth. Based on the synergistic effect of Bacillus species with metal nanoparticles, nano-biofertilizer formulations are being developed. Bacillus cells integrated into a suitable metal/polymer in the form of nanoparticles or the metabolites they produce are used as nano-bioformulations. In recent years, with the integration of nanotechnology into biofertilizer formulations, the use of preparations with increased biofertilizer efficiency has been increasing.In this thesis, a nano-bioformulation was designed using Bacillus subtilis 4-Ka-22 strain isolated from local sources and identified as PGPR and magnetic iron nanoparticles (Fe-NP). The study started with the optimization of the culture broth of B. subtilis 4-Ka-22 strain. For this purpose, culture broth optimization was performed with Surface Response Methodology in Design Expert® program. In the method, according to the maximum inhibition rate (%) and viable cell number (cfu/mL) responses of lipopeptides produced by B. subtilis 4-Ka-22 strain against three types of phytopathogenic fungi (Botrytis cinerea, Fusarium solani and Rhizoctonia solani), culture broth components were determined as 8 g molasses, 15 g soy flour, 9.5 g Monosodium glutamate (MSG), 6.6 g CaCl2 and 10 g glycerol and named as CLP production broth. Magnetic iron nanoparticles (Fe-NPs) were used as nanocomponents in the designed nano-bioformulation. The synthesis of Fe-NPs was carried out by chemical and green synthesis methods. The effect of Fe-NPs synthesized by chemical method on chitinase, chitosanase and protease enzyme activities was investigated, but no enzyme activity enhancing effect was observed.Two different iron salts (FeCl3 and FeSO4) were added to the culture broth for the synthesis of green nanoparticles in the CLP production broth of B. subtilis 4-Ka-22 strain and the effect of different concentrations of iron salts (1, 3, 5, 10, 15 and 20 mM) on the number of viable cells and magnetic particle formation was investigated. At the end of the culture process, no magnetic particle formation was observed in any of the broth, while high concentrations (10, 15 and 20 mM) of iron content caused cell death.After culturing B. subtilis 4-Ka-22 strain in CLP production broth, two different iron salt (FeCl3 and FeSO4) solutions were added to the cell-free culture broth and magnetic Fe-NP synthesis was performed with the experiment created by the Optimal (Custom) Design method in the Design Expert® program. Magnetic interaction was observed in the cell-free culture medium incubated with 15 mM FeSO4 salt at pH 13, 68°C, 48 h. The highest amount of IAA (31.23 µg/mL) and the lowest average particle diameter (718.8 d.nm) according to DLS analysis were determined in this sample. In the same conditions, the synthesis was carried out by adding 300 rpm mixing to the incubation conditions of the culture broth containing cells and FeSO4 salt and it was determined that more effective Fe-NPs were synthesized according to the increase in the amount of IAA (81.40 µg/mL). According to the results of the experiments; Fe-NPs synthesized in the culture broth of B. subtilis 4-Ka-22 strain, nano-bioformulation of Fe-NPs seems to be promising in the enrichment of biofertilizer activity.

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