Microbeads as carriers for Bacillus pumilus: a biofertilizer focus on auxin production

Abstract

The study aimed to develop a solid biofertilizer using Bacillus pumilus, focusing on auxin production to enhance plant drought tolerance. Methods involved immobilising B. pumilus in alginate-starch beads, focusing on microbial concentration, biopolymer types, and environmental conditions. The optimal formulation showed a diameter of 3.58 mm ± 0.18, a uniform size distribution after 15 h of drying at 30 °C, a stable bacterial concentration (1.99 × 10⁹ CFU g⁻¹ ± 1.03 × 10⁹ over 180 days at room temperature), a high auxin production (748.8 µg g⁻¹ ± 10.3 of IAA in 7 days), and a water retention capacity of 37% ± 4.07. In conclusion, this new formulation of alginate + starch + L-tryptophan + B. pumilus has the potential for use in crops due to its compelling water retention, high viability in storage at room temperature, and high auxin production, which provides commercial advantages.

Keywords:

• immobilisation bacteria
• biopolymers
• PGPR
• inoculants
• Biofertilizers

Acknowledgements

The authors would like to acknowledge the collabotion of Center for Spectroscopy and Microscopy (CESMI) for the SEM analysis and Prof. Myleidi Vera from the Polymer Department, Faculty of Chemistry, Universidad de Concepción.

Author contributions

Solange Benítez: design and development of the experiments, data collection, and analysis, writing and editing original draft; Rocio Carrasco: experiments and data collection; Juan Giraldo: designed the study, supervision, writing—review and editing (equal); Mauricio Schoetbitz: funding, designed the study, review, supervision and writing—review and editing (equal). This manuscript was approved for all authors.

Disclosure statement

The authors declare no conflict of interests.

Additional information

Funding

This research was supported by Projects FONDEF ID21100I50 and FONDECYT POSTDOCTORAL 3210599.