Shelf Life of Azospirillum brasilense in Alginate Beads Enriched With Trehalose and Humic Acid

Since abiotic and biotic factors can compromise the survival of bacteria and their viability, encapsulation of cells in biodegradable gel matrices, a biological macromolecule, is one alternative to have their shelf life extended. Here, it was developed a gel-based formulation of the bioinoculant Azospirillum brasilense strain AbV5 and determined the effect of trehalose and humic acid supplementation in viability and survival of bacteria. For each 2 ml of sodium alginate solution (3%), 1 ml of the inoculum was extruded in a solution containing sodium alginate complexed with calcium chloride, forming calcium alginate beads. Supplements were used in a ratio of 2:2:1. Treatments were peat; alginate; alginate + humic acid; alginate + trehalose 0.1 M; alginate + trehalose 1 M. Morphometric aspects, survival rate and viability were determined in 9 storage periods (3, 5, 7, 14, 21, 30, 45, 60, 90 days). As results, beads were able to sustain the growth of A. brasilense for 90 days. Shelf life quality decreased in all treatments and peat remained the best carrier. Encapsulation, despite promoting the greatest losses in the survival of bacteria in the first days, ensured better cell viability. Trehalose in low concentrations (0.1M) improved cell viability during storage, optimizing plant inoculation.