Enhancing sustained antimicrobial activity of <i>ε</i> -polylysine via soluble soybean polysaccharides nanoparticles

Abstract ε -Polylysine ( ε -PL) has a broad antibacterial spectrum and high antibacterial efficiency, while its antibacterial activity can be reduced due to interactions with anionic components in food matrices, leading to the formation of flocculent materials or precipitates. To overcome this issue, this study successfully prepared ε -PL-loaded soluble soybean polysaccharide nanoparticles via electrostatic complexation. Under the optimal formulation of ε -polylysine ( ε -PL) and soluble soybean polysaccharide (SSPS) with mass ratio of 1:3, pH=5 and SSPS concentration of 3 mg/mL, the size and zeta potential of the ε -PL-loaded SSPS nanoparticles ( ε -PL-SSPS-NPs) were 102 nm and −2.12 mV, while the encapsulation efficiency of ε -polylysine ( ε -PL) was 99.8 %. Transmission Electron Microscopy (TEM) revealed nanoparticles displaying uniform round shapes and smooth surfaces. Fourier-transform infrared (FTIR) spectral data confirmed the predominant role of both electrostatic attraction and hydrogen bonds in mediating ε -PL/SSPS complexation – electrostatic attraction was indicated by the weakened COO − peak of SSPS at 1,618 cm −1 , and hydrogen bonds by the broadened N –H peak of ε -PL. The ε -PL release rate of ε -PL-SSPS-NPs (59 %) was lower than that of free ε -PL (nearly 100 %) after 120 h, suggesting that the ε -PL-SSPS-NPs could achieve the sustained release of ε -PL in the simulated physiological environment. The agar diffusion assay exhibited that ε -PL-SSPS-NPs had antimicrobial activity against both bacteria and fungi, including Bacillus subtilis , Escherichia coli , and Penicillium .