Harnessing endophytic bacteria for enhanced wheat growth: extraction, optimization, and characterization of exopolysaccharides.

UNLABELLED: The extensive use of chemical inputs in modern agriculture has severely degraded soil health, threatening long-term productivity and sustainability. Microbial exopolysaccharides (EPS) are emerging as promising biostimulants due to their ability to enhance soil functionality, improve water retention, and promote plant growth. The current study focused on prospecting seed endophytic bacteria for the production of phytostimulatory exopolysaccharides. Eighty-six pearl millet seed endophytic bacteria (PMSEB) were screened for EPS production on Nutrient Agar and ATCC No.14 media, followed by extraction, partial purification, and quantification of EPS produced by selected PMSEB. Seed germination bioassay with partially purified EPS (0.2%) revealed that EPS from selected PMSEB strains exhibited a biostimulatory effect on early-stage wheat growth. A dose-dependent effect of EPS (0.25%, 0.5%, 1%) on wheat germination was also observed. Notably, EPS from MPT27, PC7N47, and PC7T5 (identified as Atlantibacter hermannii, Bacillus subtilis subsp. subtilis, and Bacillus subtilis subsp. subtilis, respectively) showed significant effects in terms of seed germination, seedling dry weight, and vigor indices. Optimal EPS production was achieved under strain-specific culture conditions, with sucrose serving as the most effective carbon source. Characterization studies revealed variation in water absorption capacity and DPPH radical scavenging capacity of EPS extracted. FTIR analysis confirmed the characteristic functional groups of polysaccharides. Monosaccharide analysis indicated that EPS from strains MPT27 and PC7N47 were heteropolysaccharides, while PC7T5 produced homopolysaccharides. These findings showed the potential of EPS from PMSEB as a promising phytostimulant for sustainable agriculture.

SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at https://doi.org/10.1007/s13205-026-05074-6.