Synthesis and Characterization of Gum Kondagogu Stabilized Zinc Oxide Nanoparticles and Its Application as an Antibacterial Agent Against Wastewaterborne Bacteria

Abstract

Wastewater recycling is one of the viable options for attaining sustainable water management. In this scenario, gum stabilized zinc oxide nanoparticles (ZnO NP) were synthesized employing the alkaline precipitation method with gum kondagogu stabilizer. Synthesized NP were characterized using UV-vis, DLS, zeta potential, XRD, FTIR, and TEM. ZnO NP exhibited an absorption peak at 351 nm in UV-vis, a zeta potential value of-35 mV, and a z-average value of 254 nm in DLS. XRD pattern showed a characteristic hexagonal wurtzite crystal structure and FTIR data indicated the capping of NP by various gum functional groups. The size of spherical NP varied from 12.4 to 35.7 nm, and the mean particle size was 24.8 ± 5.1 nm. The in vitro antibacterial activity of ZnO NP against wastewaterborne bacteria, Escherichia coli (Gram- negative) and Bacillus subtilis (Gram-positive) was studied with the resazurin broth assay. MIC values of 900 μg/mL and 900 μg/mL and MBC values of 1800 μg/mL and 900 μg/mL of ZnO NP were recorded towards E. coli and B. subtilis. Notably, ZnO NP exhibited superior bactericidal activity against B. subtilis compared to previous studies. Thus, the current study on ZnO NP mediated bacterial disinfection has wide applications in wastewater treatment and remediation of microbially contaminated effluents.

Keywords: antibacterial; tree gum; water disinfection; zinc oxide nanoparticles.

FIGURE 1

The UV–visible absorption spectra of gum kondagogu capped zinc oxide nanoparticles (ZnO NP) synthesized with zinc acetate (10 mM) and sodium hydroxide (20 mM) at (a) different concentrations (0.1%–0.5%) of gum and (b) optimal concentration of 0.5% gum. Inset: (i) ZnO NP powder stabilized with 0.5% gum and (ii) aqueous solution of the ZnO NP.

FIGURE 2

The XRD pattern of gum stabilized ZnO NP.

FIGURE 3

The FTIR spectra of (a) gum kondagogu and (b) gum kondagogu‐ capped ZnO NP.

FIGURE 4

The (a) particle size distribution and (b) zeta potential of gum‐ capped ZnO NP.

FIGURE 5

The TEM image of gum‐ capped ZnO NP at (a) 100 nm scale, (b) particle size histogram, and (c) respective selected area electron diffraction (SAED) pattern.

FIGURE 6

The antibacterial action of ZnO NP towards wastewaterborne bacterial pathogens, (a) Escherichia coli ATCC 25922 and (b) Bacillus subtilis ATCC 6633 in resazurin broth assay at (i) 0 μg/mL, (ii) 900 μg/mL, (iii) 1800 μg/mL, (iv) 2700 μg/mL, (v) 3600 μg/mL, and (vi) ciprofloxacin (10 μg/mL).

FIGURE 7

Bactericidal activity of ZnO NP towards E. coli visualized in terms of bacterial colony growth at (a) 0 μg/mL, (b) 900 μg/mL, (c) 1800 μg/mL, (d) 2700 μg/mL, (e) 3600 μg/mL, and (f) ciprofloxacin (10 μg/mL).

FIGURE 8

Bactericidal activity of ZnO NP towards B. subtilis visualized in terms of bacterial colony growth at, (a) 0 μg/mL, (b) 900 μg/mL, (c) 1800 μg/mL, (d) 2700 μg/mL, (e) 3600 μg/mL; and (f) ciprofloxacin (10 μg/mL).

FIGURE 9

The stability of synthesized ZnO NP solutions at varying (a) pH (1‐12) and (b) (30°C–100°C), in terms of measured zeta potential values.