Shelf life enhancement of plant growth promoting rhizobacteria using a simple formulation screening method

Abstract

Plant growth promoting rhizobacteria (PGPR) are a specific group of bacteria interacting beneficially with plants. Among the known PGPRs, the species Pseudomonas fluorescens and Burkholderia pyrrocinia have been highlighted in both growth promotion and control of rice diseases. Ensuring the stability of the microorganism during production, formulation, distribution and storage has been a challenge for these species. In this context, the objective of this work was to develop liquid formulations, through a simplified process, that allows increase in the shelf life of these rhizobacteria for commercial application. Both bacteria were tested in 32 formulations under two storage temperature conditions: 8 and 28°C, resulting in 64 treatments for each species, which were evaluated for 180 days. Combinations of the adjuvants: molasses, glycerol, NaCl, PVP, MgSO 4 , K 2 HPO 4 and yeast extract were evaluated. Formulations containing molasses, stored at 8°C, were considered the most efficient in maintaining microbial viability. The method used was considered efficient to select three formulations that allowed maintenance of the concentration of viable cells of P. fluorescens and B. pyrrocinia in 10 8 cfu.mL -1 , for at least 90 and 150 days, respectively, not interfering with bacterial action potential.

Plant Associated Rhizobacteria for Biocontrol and Plant Growth Enhancement

“…Achieving low-cost production at large scale is a difficult task, but reachable with careful research effort (Trujillo-Roldán et al, 2013;Carrasco-Espinosa et al, 2015;Kang et al, 2017). Liquid formulations are the most popular forms (Lee et al, 2016); many researchers tried to increase the shelf life of PGPR through lowering storage temperature and/or modifying the combinations of additives (Arriel-Elias et al, 2018;Berger et al, 2018).…”

Optimization of the Extraction Process and Application of Bacterial Extracts in the Control of Brown Spot and Leaf Blast in Rice Culture

“…Other works of the same research group revealed that these same isolates are growth promoters in rice, soybean and bean crops, antagonists to some phytopathogens such as M. oryzae and B. oryzae and resistance inducers. (Filippi et al 2011;Sousa et al 2017;Côrtes et al 2015;Nascente et al 2017;Sperandio et al 2017;Arriel-Elias et al, 2018;Arriel-Elias et al 2019;Silva et al 2020;Rezende et al 2021). However, complete genome characterization and chemical characterization of the metabolites of both bacterial isolates had not been performed so far.…”

“…Preparation of bacterial suspension: a cell suspension of the B. pyrrocinia and Bacillus sp. isolate was transferred to a 500 ml Erlenmeyer ask, containing 200 ml of nutrient broth culture medium, prepared according to Arriel-Elias et al (2018). The bottles were under constant stirring at 150 rpm, for 48 h at 28°C.…”

Humic Acid-Amended Formulation Improves Shelf-Life of Plant Growth-Promoting Rhizobacteria (PGPR) Under Laboratory Conditions

“…This phenomenon is explained by the time required for microbial cells to adapt and proliferate, even when stored without agitation or at temperatures other than optimal. Since their metabolism is not disrupted, the cells continue to ingest the nutrients from the formulas, albeit at a slower rate (Arriel-Elias et al, 2018;Tapia et al, 2020). So, the degradation rate shows when the microbe's nutrient requirements start to decline.…”

“…Therefore, to prolong the shelf-life, an optimized formulation must be developed (Mahalakshmi et al, 2019). Moreover, the formulation should normally include the active component in an appropriate carrier and additives to stabilize and safeguard the microbial cells throughout storage, transportation, and the targeted root zone (Arriel-Elias et al, 2018).…”