Optimized biosynthesis of bioactive silver nanoparticle-kombucha cellulose nanocomposites for enhanced antimicrobial applications

Sustainable biosynthesis of monodisperse, bioactive silver nanoparticles (AgNPs) integrated with nanofabricated kombucha SCOBY cellulose membrane (KC) was achieved using the endophytic fungus A. fumigatiaffinis PP235788.1 fungal filtrate. This study is the first to optimize AgNP synthesis via full-factorial design of experiments (DOEs) and response surface methodology (RSM), identifying ideal conditions (2 mmol L^-1 AgNO₃, pH 8 and 60 °C). Characterization revealed spherical AgNPs (14.50 ± 0.58 nm) and AgNPs@KC composites (17.88 ± 0.36 nm); SEM imaging demonstrates the successful fusion of AgNPs within KC's fibrous membrane, creating a seamlessly integrated nanocomposite with enhanced functional architecture. The formed nanoparticles were composed of crystalline mettalic silver, as varified by XRD (detected planes at 111, 200, and 220), and were stabilized by amide groups, as identified by FTIR spectroscopy. The biosynthesized AgNPs demonstrated a dose-dependent antimicrobial activity with an increase in inhibition zones from 11.8 ± 2.1 mm at 10 µg/mL to 36.1 ± 0.4 mm at 100 µg/mL for E. coli and from 9.8 ± 2.9 mm to 34.33 ± 1.2 mm for Bacillus subtilis. Fungal pathogens displayed diminished sensitivity, with Aspergillus niger achieving maximum inhibition (25.7 ± 0.3 mm) at 100 µg/mL, whereas Candida spp. necessitated ≥ 60 µg/mL for observable inhibition zones. AgNPs@KC composites demonstrated broad-spectrum efficacy against 12 pathogens (ANOVA, p < 0.001, R² > 95%), with maximal activity against E. coli, B. subtilis, and A. niger (33.0 ± 0.2 mm). These findings highlight the integration of mycosynthesized AgNPs with kombucha SCOBY cellulose membranes, offering a novel and unique platform for antimicrobial approaches with exceptional purity and distinctive physiological characteristics. KEY POINTS: • AgNPs optimized via DOE/RSM. • AgNPs@KC shows potent antimicrobial activity. • Novel mycosynthesis of AgNPs with KC membranes.