Gel of Encapsulated Azotobacter vinelandii Enhance Plant Growth and Modulate Soil Microbial Communities

Gel of Encapsulated Azotobacter vinelandii Enhance Plant Growth and Modulate Soil Microbial Communities

Abstract

The increasing requirements for sustainable agricultural practices require the implementation of innovative methodologies to achieve yields like those achieved with conventional fertilizers, thus improving the environmental sustainability of agricultural processes and preventing irreversible degradation of arable land. Among these novel technologies is the development of biofertilizers that inoculate soil with plant growth promoting rhizobacteria (PGPR), a diverse group of microorganisms recognized for their beneficial contributions, including nitrogen fixation, phosphate solubilization, the production of siderophores and phytohormones [1], as well as the synthesis of protective exopolysaccharide alginate and intracellular polyhydroxyalkanoates that serve as a carbon source under stress conditions [2]. The research presents an innovative method for biofertilizer production that uses Azotobacter vinelandii for in situ self-encapsulation within a gel carrier through the crosslinking of alginate synthesized during the bacterial cultivation process. This novel approach streamlines the preparation protocol, presenting opportunities for cost reduction and enhancing the overall competitiveness of the process. To validate this concept, selected bacterial strains were subjected to gelation experiments under conditions promoting alginate gel formation, using 2% (w/w) CaCl₂ as a cross-linking agent. Azotobacter vinelandii CCM 289 was chosen based on its superior alginate production, efficient gelation performance, and demonstrated potential for synthesizing indole-3-acetic acid and siderophores. A total of 3 cultivation experiments were conducted on a model plant Lactuca sativa, incorporating various carrier compositions (cells in PBS; gel excluding cells; gel including cells; freeze-dried gel with cells; negative control without any addition). The main variations among the cultivation conditions were attributed to the different quality of the soil and the variations in the irrigation rates. The growth experiment was carried out within a fume hood adapted to a cultivation box equipped with regulated irrigation and illumination, along with the control of temperature and humidity parameters. As soil quality and the frequency of irrigation decreased in the experimental trials, the differences among the various groups became more apparent, accompanied by a significant improvement in fundamental growth metrics (fresh/dry weight, lengths of various plant parts), in addition to favorable alterations in the composition of the soil microbiome.

The increasing requirements for sustainable agricultural practices require the implementation of innovative methodologies to achieve yields like those achieved with conventional fertilizers, thus improving the environmental sustainability of agricultural processes and preventing irreversible degradation of arable land. Among these novel technologies is the development of biofertilizers that inoculate soil with plant growth promoting rhizobacteria (PGPR), a diverse group of microorganisms recognized for their beneficial contributions, including nitrogen fixation, phosphate solubilization, the production of siderophores and phytohormones [1], as well as the synthesis of protective exopolysaccharide alginate and intracellular polyhydroxyalkanoates that serve as a carbon source under stress conditions [2]. The research presents an innovative method for biofertilizer production that uses Azotobacter vinelandii for in situ self-encapsulation within a gel carrier through the crosslinking of alginate synthesized during the bacterial cultivation process. This novel approach streamlines the preparation protocol, presenting opportunities for cost reduction and enhancing the overall competitiveness of the process. To validate this concept, selected bacterial strains were subjected to gelation experiments under conditions promoting alginate gel formation, using 2% (w/w) CaCl₂ as a cross-linking agent. Azotobacter vinelandii CCM 289 was chosen based on its superior alginate production, efficient gelation performance, and demonstrated potential for synthesizing indole-3-acetic acid and siderophores. A total of 3 cultivation experiments were conducted on a model plant Lactuca sativa, incorporating various carrier compositions (cells in PBS; gel excluding cells; gel including cells; freeze-dried gel with cells; negative control without any addition). The main variations among the cultivation conditions were attributed to the different quality of the soil and the variations in the irrigation rates. The growth experiment was carried out within a fume hood adapted to a cultivation box equipped with regulated irrigation and illumination, along with the control of temperature and humidity parameters. As soil quality and the frequency of irrigation decreased in the experimental trials, the differences among the various groups became more apparent, accompanied by a significant improvement in fundamental growth metrics (fresh/dry weight, lengths of various plant parts), in addition to favorable alterations in the composition of the soil microbiome.

Azotobacter vinelandii, alginate, polyhydroxyalkanoates, gels, encapsulation

Azotobacter vinelandii, alginate, polyhydroxyalkanoates, gels, encapsulation

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

01.10.2025

Rectorate of Universidade NOVA de Lisboa

Lisbon, Portugal

Book of abstracts ESBP 2025

56

57

204

https://www.esbp2025.org/book-of-abstracts