Tannin-Derived Phosphatase-Mimicking Carbon Nanozyme with Dual Antimicrobial and Plant Growth-Promoting Functionalities for Sustainable Agriculture

The development of eco-friendly agents that integrate antimicrobial efficacy with crop growth promotion remains a challenge in sustainable agriculture. In this study, a sulfur- and nitrogen-doped phosphatase non-metallic nanozyme was synthesized via a green route using a tannin-rich root extract of Limonium otolepis (LR). Successful incorporation of heteroatom dopants and phenolic groups from LR was confirmed by FT-IR and X-ray photoelectron spectroscopy (XPS) analysis. The resulting nanoparticle LRS-NPs exhibited a complementary phosphatase activity along with a synergistic antimicrobial effect against Escherichia coli ( E. coli ) and Staphylococcus epidermidis ( S. epidermidis ), with a minimum inhibitory concentration (MIC) of 94 μg/mL . Scanning electron microscopy (SEM) images of treated bacterial cells showed clear disruption of the outer membrane of E. coli and damage to the cell walls of both bacterial models. Notably, even at a highly diluted concentration (1.35 μg/mL), LRS-NPs also promoted the growth of mung bean ( Vigna radiata ) sprouts compared to controls grown in deionized (DI) water. With its dual functionality—low-concentration plant biostimulation and bacterial membrane-targeting antimicrobial action—LRS-NPs represent a promising green nano-platform for agricultural applications within the framework of sustainable agriculture and the circular economy.