Development of an encapsulated biofertilizer using a sodium alginate-corn starch-chitosan nanoparticle matrix for improved shelf life and controlled delivery of Serratia sp. ABU35 to enhance growth performance of guava (Psidium guajava L.)
Abstract
Sustainable alternatives to synthetic fertilisers are urgently needed to mitigate their ecological footprint, yet the practical deployment of microbial biofertilisers is constrained by poor survival and inconsistent performance under field conditions. Encapsulation formulations have been explored to enhance microbial stability and support efficient rhizosphere colonization, however their application in perennial horticultural crops remains insufficiently studied. To address this gap, we developed an encapsulated formulation of Serratia sp. strain ABU35 isolated from guava endorhizosphere, using sodium alginate-corn starch matrix incorporated with chitosan nanoparticles (CNPs) and validated its performance in guava (P. guajava L.) through one-year pot culture trial. The optimized formulation exhibited improved encapsulation efficiency (99.23 ± 1.56%), swelling capacity (156.67 ± 2.40%), moisture retention (78.33 ± 1.16%), and a sustained release profile (108 CFU mL−1). Encapsulated Serratia sp. strain ABU35 maintained high viability during storage, retaining 8.94 ± 0.25 log CFU g−1 after 12 months (P < 0.001). The produced microcapsules were ovoid to near-spherical shape and further characterized by Field Emission Scanning Electron Microscopy (FE-SEM), X-ray Diffraction (XRD), and Fourier Transform Infrared Spectroscopy (FTIR). The encapsulated strain retained its plant growth-promoting and biocontrol potential after long-term storage. Pot trials showed significant enhancement in plant growth parameters (P < 0.001), rhizospheric microbial populations (P < 0.001), and soil available N, P, and K (P < 0.001), relative to plants treated with liquid formulation and untreated control. By demonstrating year-long shelf stability and functional efficacy under controlled pot conditions, this study highlights the potential of encapsulation as a promising strategy for perennial horticultural crops; however, further validation under field conditions is required before practical application as a sustainable alternative to chemical inputs.