Living Gels: Self formed alginate matrices for sustainable agriculture by Azotobacter vinelandii

Living Gels: Self formed alginate matrices for sustainable agriculture by Azotobacter vinelandii

Abstrakt

The increasing pressure for sustainable and environmentally friendly farming practices has created a strong demand for innovative technologies capable of achieving yields comparable to those obtained with conventional fertilizers, while preserving soil health and preventing irreversible degradation of fertile land. Among such approaches are biofertilizers that inoculate soil with plant growth-promoting rhizobacteria (PGPR), a diverse group of microorganisms known for their beneficial contributions to plant nutrition and stress resilience. These include nitrogen fixation, phosphate solubilization, and the synthesis of siderophores and phytohormones. Many PGPR, including Azotobacter vinelandii, also produce protective extracellular polysaccharides such as alginate and intracellular polyhydroxyalkanoates (PHA), which serve as carbon storage granules under stress conditions. This study presents an innovative method for biofertilizer production using Azotobacter vinelandii capable of in situ self-encapsulation within a gel carrier formed through the crosslinking of alginate produced during bacterial cultivation. This self-gelation concept, proposed by our group, simplifies the preparation of bioinoculants, reduces production costs, and enhances the efficiency and sustainability of bacterial formulation. To validate this approach, selected A. vinelandii strains (DSM 87, DSM 720, and CCM 289) were subjected to gelation experiments under alginate crosslinking conditions, using 2% (w/w) CaCl₂ as a cross-linker. Among them, A. vinelandii CCM 289 demonstrated superior alginate production, gelation performance, and plant growth-promoting potential. The biological activity of the produced bioinoculants was assessed by wide variety of plant-growth promoting experiments (qualitative assays for phosphate solubilization, and spectrophotometric determinations of indole-3-acetic acid and siderophore production). Plant cultivation experiments were carried out using lettuce and maize under controlled irrigation and illumination, employing different carrier compositions (cells in PBS, gel without cells, gel with cells, freeze-dried gel with cells, and negative control without inoculation). Variations in soil quality and irrigation frequency were found to influence plant growth response and soil microbial composition. As these conditions became more limiting, the benefits of the bacterial treatments became increasingly evident, reflected in higher fresh and dry biomass, longer plant components, and favorable shifts in the soil microbiome. The root architecture of the plant was subsequently examined employing ImageJ analysis. Through this methodology, the variations in root system morphology were documented. The results confirm that self-encapsulated Azotobacter vinelandii bioinoculants produced by in situ alginate gelation offer a promising, sustainable alternative for enhancing plant growth and soil health in green agriculture.

The increasing pressure for sustainable and environmentally friendly farming practices has created a strong demand for innovative technologies capable of achieving yields comparable to those obtained with conventional fertilizers, while preserving soil health and preventing irreversible degradation of fertile land. Among such approaches are biofertilizers that inoculate soil with plant growth-promoting rhizobacteria (PGPR), a diverse group of microorganisms known for their beneficial contributions to plant nutrition and stress resilience. These include nitrogen fixation, phosphate solubilization, and the synthesis of siderophores and phytohormones. Many PGPR, including Azotobacter vinelandii, also produce protective extracellular polysaccharides such as alginate and intracellular polyhydroxyalkanoates (PHA), which serve as carbon storage granules under stress conditions. This study presents an innovative method for biofertilizer production using Azotobacter vinelandii capable of in situ self-encapsulation within a gel carrier formed through the crosslinking of alginate produced during bacterial cultivation. This self-gelation concept, proposed by our group, simplifies the preparation of bioinoculants, reduces production costs, and enhances the efficiency and sustainability of bacterial formulation. To validate this approach, selected A. vinelandii strains (DSM 87, DSM 720, and CCM 289) were subjected to gelation experiments under alginate crosslinking conditions, using 2% (w/w) CaCl₂ as a cross-linker. Among them, A. vinelandii CCM 289 demonstrated superior alginate production, gelation performance, and plant growth-promoting potential. The biological activity of the produced bioinoculants was assessed by wide variety of plant-growth promoting experiments (qualitative assays for phosphate solubilization, and spectrophotometric determinations of indole-3-acetic acid and siderophore production). Plant cultivation experiments were carried out using lettuce and maize under controlled irrigation and illumination, employing different carrier compositions (cells in PBS, gel without cells, gel with cells, freeze-dried gel with cells, and negative control without inoculation). Variations in soil quality and irrigation frequency were found to influence plant growth response and soil microbial composition. As these conditions became more limiting, the benefits of the bacterial treatments became increasingly evident, reflected in higher fresh and dry biomass, longer plant components, and favorable shifts in the soil microbiome. The root architecture of the plant was subsequently examined employing ImageJ analysis. Through this methodology, the variations in root system morphology were documented. The results confirm that self-encapsulated Azotobacter vinelandii bioinoculants produced by in situ alginate gelation offer a promising, sustainable alternative for enhancing plant growth and soil health in green agriculture.

alginate, polyhydroxyalkanoates, Azotobacter vinelandii, gels, encapsulation

alginate, polyhydroxyalkanoates, Azotobacter vinelandii, gels, encapsulation

SÚKENÍK, M.; ČERNAYOVÁ, D.; SEDLÁČEK, P.; HLAVÁČKOVÁ, B.; KALINA, M.

27.11.2025

Vysoké učení technické v Brně

Brno

978-80-214-6388-2

studentská odborná konference CHEMIE JE ŽIVOT 27—11— 2025

65

65

91

https://www.fch.vut.cz/vav/konference/sok/vystupy/sok-2025-sbornikabstraktu-pdf-p321225