Revolutionizing Sustainable Agriculture: Harnessing Macrofungi and Bacterial Systems for Eco-Friendly Silver Nanoparticle Synthesis and Enhanced Plant Growth

Nanotechnology offers transformative potential in modern agriculture, providing sustainable alternatives to conventional agrochemicals. This review examines the synthesis, characterization, and applications of silver nanoparticles (AgNPs), emphasizing biologically mediated “green synthesis” via fungi and bacteria. These eco-friendly approaches exploit microbial reductive enzymes, such as nitrate reductase and oxidoreductases, to convert silver ions (Ag⁺) into nanoparticles, avoiding the environmental and energetic drawbacks of chemical and physical methods. AgNPs exhibit strong antimicrobial activity through membrane disruption, reactive oxygen species (ROS) generation, and enzyme inhibition, making them effective against phytopathogens. Additionally, they promote seed germination, root elongation, and modulate phytohormone pathways, benefits attributed to their high surface-area-to-volume ratio and tunable physicochemical properties. Both intracellular and extracellular biosynthetic routes are discussed, with evaluation of their scalability, stability, and yield. Characterization techniques, including UV-vis spectroscopy, SEM, XRD, FTIR, and AFM, provide insights into size (5–100 nm), shape, crystallinity, and dispersity, key factors influencing efficacy. In soil systems, AgNPs function as nanopesticides and nanofertilizers, enhancing nutrient bioavailability and reducing agrochemical runoff. Advances focus on optimizing microbial strains (e.g., Bacillus subtilis, Aspergillus niger), controlling zeta potential, and surface functionalization for targeted applications. Challenges such as phytotoxicity, bioaccumulation, and regulatory concerns persist. By integrating over 50 studies, this review underscores AgNPs’ potential to support resilient, resource-efficient farming while highlighting the need for standardized protocols, long-term field assessments, and comprehensive safety evaluations to realize nanotechnology’s full agricultural promise.