Self-entrapment of Plant Growth Promoting Rhizobacteria by gelation of their exopolysaccharides

abstrakt

angličtina

Recently, high demands have been placed on sustainable farming to achieve similar yields using less conventional fertilizers, because of the effort to improve the environment and avoid irreversible damage to fertile land. The aim of this work was to select and characterize specific mechanisms in plant growth promoting bacteria (PGPR), commonly found in the rhizosphere of plants. The selected PGPR strain, Azotobacter vinelandii, is credited with a number of interesting plant growth-promoting mechanisms, such as nitrogen fixation, phosphate utilization, production of siderophores and phytohormones, and can produce the protective exopolysaccharide alginate and intracellular polyhydroxyalkanoates in the form of granules serving as a carbon source pool. An original concept of bacteria self-encapsulation via cross-linking of alginate directly produced during their culturing was proposed by our group for the preparation of gel bioinoculants based on these PGPRs. To validate the efficacy of this concept, all selected strains had to be subjected to gelation experiments with the crosslinking agent CaCl2 2 wt. % under alginate gel formation. Three specific strains of Azotobacter vinelandii DSM 87, DSM 720, and CCM 289 were selected for the preparation and characterization of the bioinoculants. The material properties of the formed gels were characterized by oscillatory rheometry (amplitude test). All strains were subjected to gravimetric determination of alginate and biomass concentrations. Flow cytometry with fluorescent probe PI was used to verify cell viability immediately after culturing. To confirm the biological activity of the bioinoculants, the ability of all strains to dissolve and utilize phosphate from the agar medium was qualitatively assayed. Furthermore, the production of indole-3-acetic acid was spectrophotometrically studied for all strains. The production of siderophores was also verified qualitatively and quantitatively. Pilot cultivation experiments on the lettuce (Lactuca sativa) plant were performed with the addition of both liquid and gel carrier PGPR compositions; as a negative control, the plant was left without the addition of carrier PGPR composition. The diversity of soil microbiomes collected from the soil without the addition of PGPR composition, with the addition of liquid PGPR composition, and with the addition of gel PGPR composition was analyzed using BIOLOG EcoPlate™ plates. The content of chlorophyll a, chlorophyll b, and carotenoids in the leaves was spectrophotometrically detected in plants.

Azotobacter vinelandii, alginate, polyhydroxyalkanoates, gels, encapsulation

SÚKENÍK, M.;ČERNAYOVÁ, D.;SEDLÁČEK, P.

30. 11. 2023

Vysoké učení technické v Brně, Fakulta chemická

Brno

978-80-214-6204-5

Chemie je život 2023

1.

první

66

67

2

https://www.fch.vut.cz/vav/konference/sok/vystupy/sbornik-abstraktu-2023-na-web-pdf-p251584