الفهرس 
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Abstract
Avicin A is a pediocin-like bacteriocin that displays a potent antimicrobial activity (AMA) against many species of Gram-positive bacteria. In this study, enhancements of the yield and antibacterial activity duration of avicin A were accomplished using fractional factorial design (FFD) and layered double hydroxide (LDH) nanoparticles. To achieve the first goal, potential factors affecting bacteriocin production were selected for FFD. By a 25-1 FFD, high pH was shown to have a positive effect on avicin A activity, while temperature and duration of incubation, as well as peptone nitrogen sources all had negative effects. Based on the results from interaction terms, optimum bacteriocin production and activity (2560 BU/ml) were observed after 30 h of incubation at 30°C, with pH adjustment at 7, and in the presence of 2 g mannitol as carbon source and 2.2 g peptone as nitrogen source. To achieve the second goal, three different types of LDHs were prepared, characterized, and used for the first time to form nanocomposites with avicin A. The X-ray diffraction (XRD) and the Fourier transform infrared (FT-IR) spectroscopy indicated that avicin A was successfully conjugated with LDHs without side reactions. Among all the tested LDHs preparations, only avicin A ZnAl-CO3 LDH nanocomposite demonstrated a potent AMA against Lactobacillus sakei LMGT 2313 that lasted for at least 24 days, as compared to the values of 6 and 15 days observed with the free avicin A that have been stored at room temperature and at 4°C, respectively. In conclusion, these promising results provide further evidence that manipulating the growth conditions and media composition and conjugation with LDHs can be used to improve bacteriocins production and stability, and hence pave the way for extending their applications in food and biomedical industries.