Azotobacter-Based Biofertilizers: Mechanism of Plant Growth Promotion, Agricultural Applications and Future Perspectives

The increasing use of chemical fertilizers has raised serious environmental concerns, highlighting the need for sustainable and eco-friendly alternatives. Azotobacter spp. are free-living, nitrogen-fixing bacteria that play an important role in improving soil fertility and promoting plant growth. These bacteria convert atmospheric nitrogen into biologically available forms and enhance plant development through the production of phytohormones, phosphate solubilization, siderophore production, and biocontrol activities. This review discusses the classification, structural features, nitrogen fixation process, and plant growth-promoting activities of Azotobacter species. It also discusses their applications as biofertilizers in sustainable agriculture, particularly their ability to improve nutrient availability, support root development, enhance crop productivity, and contribute to soil health. Furthermore, the comparative advantages of Azotobacter over other beneficial bacteria, including Rhizobium, Azospirillum, Bacillus, and Pseudomonas, are highlighted. Beyond agriculture, Azotobacter has attracted attention for its pharmaceutical and industrial applications. Its production of biopolymers such as alginate and polyhydroxybutyrate (PHB) offers potential applications in drug delivery systems, wound dressings, tissue engineering, and biodegradable materials. Other valuable products, including vitamins, melanin, enzymes, and biosurfactants, further demonstrate its biotechnological importance. Despite these promising applications, challenges such as inconsistent field performance, formulation limitations, storage stability, and inadequate farmer awareness restrict its widespread adoption. Future research focusing on genetic improvement, advanced formulation techniques, nano-encapsulation, and microbial co-inoculation may enhance its effectiveness and commercial potential. Overall, Azotobacter represents a multifunctional microorganism with considerable promise for sustainable agriculture, pharmaceutical biotechnology, and environmentally responsible industrial development.