One-pot microbial approach to synthesize carbon dots from baker's yeast-derived compounds for the preparation of antimicrobial membrane

Multifunctional carbon dots (CDs) were synthesized hydrothermally from secreted metabolites (so-called postbiotics) of baker's yeast. The CDs were verified and characterized by particle size analyzer, transmission electronic microscopy, UV–visible/fluorescence, Fourier-transform infrared, and X-ray photoelectron spectroscopic. Homogeneous N and P-doped CDs (∼4.1 nm) with abundant functional groups showed a dose-dependent antimicrobial activity on Gram-positive, Gram-negative, and fungal strains. A concentration-dependent antioxidant power based on reducing the power of iron in the presence of CDs was reported. CDs were found to be non-toxic at concentrations below 3.5 mg/mL in the human colon cancer cell line (HCT-116) and TM4 cells (mouse Sertoli cell line). Moreover, CDs were used for the fabrication of antimicrobial bacterial nanocellulose membranes. Biocellulose-CDs membrane depicted broad-spectrum antimicrobial activity on nine selected bacterial and fungal strains. Taken together, the synthesized CDs and biocellulose membrane could be considered as potential antimicrobial/antioxidant additive and antimicrobial packaging material, respectively.