Impact of hydrogel-based bioformulation of drought tolerant Pseudomonas aeruginosa and Bacillus cereus consortia for Iron and Zinc accumulation in Vigna unguiculata under water stress

Drought stress severely constrains crop productivity in arid regions. This study developed a novel alginate-CMC hydrogel bioformulation (Ag-BPW), using fermented banana peel water as the aqueous phase, to enhance drought tolerance and micronutrient biofortification in cowpea beans. A consortium (CSM2) of Pseudomonas aeruginosa and Bacillus cereus along with siderophore-rich cell-free supernatant (CFSS), was encapsulated within the hydrogel. CSM2 exhibited strong PGP traits, including ACC deaminase activity, phosphate solubilization, EPS synthesis, and IAA production, further enhanced under PEG-induced osmotic stress. Pot trials with Vigna unguiculata , under drought conditions showed the Ag-BPW bioformulation significantly improved seed germination (1.9-fold), plant length (74%), chlorophyll content (> 2-fold), and relative water content (30%) compared to untreated controls. Enzymatic antioxidant and non-enzymatic antioxidants were markedly elevated. Grain iron and zinc concentrations increased by ~ 66% and ~ 99.6%, respectively compared with control, under terminal drought. The Ag-BPW bioformulation represents a biodegradable, multi-functional approach that simultaneously mitigates drought stress and biofortifies legumes.