Antimicrobial Activity of Nano-GeO2/CTAB Complex Against Fungi and Bacteria Isolated from Paper

Abstract

Microbial attack, particularly fungal degradation of cellulose, is a leading cause of paper damage. To address fungal spores and the rising concern of microbial drug resistance, a nano-Germanium dioxide (GeO₂)/cetyltrimethylammonium bromide (CTAB) complex (nano-GeO₂/CTAB complex) with potent antibacterial properties was synthesized. Its inhibitory effects were evaluated against bacteria, including Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli, as well as fungi isolated from paper (Fusarium spp., Aspergillus spp., and Penicillium citrinum). The nano-GeO₂/CTAB complex exhibited significant (p < 0.05) inhibitory effects against S. aureus and E. coli. Moreover, a 60 min treatment with 1 mg/mL of the complex significantly inhibited the growth of all tested fungi and reduced their biomass after five days of culture, while 4 mg/mL completely deactivated spores. Filter paper pre-treated with the nano-GeO₂/CTAB complex showed complete resistance to microbial attack, exhibiting no fungal growth and a clear inhibition zone devoid of bacterial growth. In contrast, untreated controls displayed fungal coverage exceeding 95% within five days. These findings highlight the nano-GeO₂/CTAB complex as a promising antimicrobial agent for protecting paper materials from microbial degradation.

Keywords: antibacterial; antifungal; nano-GeO2/CTAB complex; paper protection; spore germination.

Figure 1

Morphology and element distribution of nano-GeO₂/CTAB complex; (a) TEM morphology of nano-GeO₂/CTAB complex; (b) elements on the surface of nano-GeO₂/CTAB complex and the content of each element; (c) element distribution on the surface of nano-GeO₂/CTAB complex. Kα and Lα were shown different electron energy levels of the K shell and L shell, respectively.

Figure 2

Nano−GeO₂/CTAB complex characterization; (a) nano−GeO₂/CTAB complex FTIR spectra; (b) nano−GeO₂/CTAB complex XRD characterization; (c) nano−GeO₂/CTAB complex ZETA potential; (d) nano−GeO₂/CTAB complex transmittance.

Figure 3

Inhibitory effects of nano−GeO₂/CTAB complex to Gram−negative and Gram−positive bacteria. (a) Growth curve of E. coli treated with 0 μg/mL, 10 μg/mL, 20 μg/mL, 30 μg/mL, and 40 μg/mL nano−GeO₂/CTAB complex for 30 min; (b) growth curve of S. aureus treated with 0 μg/mL, 20 μg/mL, 40 μg/mL, 60 μg/mL, and 80 μg/mL nano−GeO₂/CTAB complex for 30 min; (c) SEM images of E. coli and S. aureus treated with 1 mg/mL nano−GeO₂/CTAB complex at 25 °C for 30 min.

Figure 4

Effects of nano−GeO₂/CTAB complex treatment on the cellulase activity of Fusarium, Aspergillus, and P. citrinum. (a) Cellulase decomposition area of Fusarium; (b) cellulase decomposition area of Aspergillus; (c) cellulase decomposition area of P. citrinum; (d) effects of nano−GeO₂/CTAB complex treatment on the cellulase activity of Fusarium, Aspergillus, and P. citrinum. When the same bacterial strain is treated with nano−GeO₂/CTAB complex, different letters on each bar indicate a significant difference in cellulase activity (p < 0.05).

Figure 5

Resistance of filter paper treated with nano−GeO₂/CTAB complex to the attack of fungi and bacteria. (a) Resistance of filter paper treated with nano−GeO₂/CTAB complex to Fusarium attack; (b) resistance of filter paper treated with nano−GeO₂/CTAB complex to Aspergillus attack; (c) resistance of filter paper treated with nano−GeO₂/CTAB complex to P. citrinum attack. (d) Resistance of filter paper treated with nano−GeO₂/CTAB complex to Pseudomonas attack.

Figure 6

Effects of treatment with nano−GeO₂/CTAB complex on the spore germination rate of Fusarium, Aspergillus, and P. citrinum. (a) Effects of treatment with nano−GeO₂/CTAB complex for 0 min, 10 min, 20 min, 30 min, and 60 min on the germination rate of Fusarium spores; (b) effects of treatment with nano−GeO₂/CTAB complex for 0 min, 10 min, 20 min, 30 min, and 60 min on the germination rate of Aspergillus spores; (c) effects of treatment with nano−GeO₂/CTAB complex for 0 min, 10 min, 20 min, 30 min, and 60 min on the germination rate of P. citrinum spores.

Figure 7

Effects of treatment with different concentrations of nano−GeO₂/CTAB complex on the biomass of Fusarium, Aspergillus, and P. citrinum. (a) Effects of treatment with different concentrations of nano−GeO₂/CTAB complex on the biomass of Fusarium; (b) effects of treatment with different concentrations of nano−GeO₂/CTAB complex on the biomass of Aspergillus; (c) effects of treatment with different concentrations of nano−GeO₂/CTAB complex on the biomass of P. citrinum.