The molecular mass of S07-2 was 905.6 Da as determined by MS. The S07-2 compound was resistant
to high temperatures (up to 100 °C) and could withstand a wide range of pH from 3 to 10. In addition, its antibacterial activity was preserved after treatment with proteases. Biochemical characterization revealed its cyclic peptide structure. This compound showed a bactericidal effect against important food-spoilage bacteria and food-borne pathogens including Listeria monocytogenes and Enterococcus faecalis with lethal concentration values of 62.5 μg mL−1 and against Salmonella enteritidis at a concentration of 31.25 μg mL−1. However, no cytotoxic effect against human RNA Synthesis inhibitor erythrocytes was recorded. Furthermore, the S07-2 compound displayed a remarkable Fe2+-chelating activity (EC50=9.76 μg mL−1)
and 1-diphenyl-2-picrylhydrazyl-scavenging capacity (IC50=65 μg mL−1). All these chemical and biological features make S07-2 a useful compound in the food industry as a natural preservative. The Gram-positive bacterium Bacillus subtilis produces a large number of bioactive peptides classified as ribosomal or nonribosomal peptides according to their biosynthesis pathway (Tamehiro et al., 2002). Nonribosomal bioactive peptides exhibit antimicrobial properties and play crucial roles in suppressing microbial competitors. Peptide antibiotics represent the predominant Alectinib concentration class of antimicrobial molecules produced by B. subtilis species (Hagelin et al., 2004;
Stein, 2005). Moreover, these species produce other bioactive molecules such as siderophores with iron-chelating properties. The catecholic siderophore bacillibactin is produced under iron-limited growth conditions (May et al., 2001). Sequestration of mobile iron plays a crucial role in reducing the occurrence of free radicals (Lin et al., 2006; Moktan et al., 2008). Free radicals or reactive oxygen species are known to cause oxidative damage to biological macromolecules, leading to a number of disorders including cancer, atherosclerosis, cardiovascular diseases, aging and inflammatory diseases (Chew et al., 2008). Synthetic antioxidants that have been extensively used in industrial processing are being investigated for their toxic and carcinogenic effects (Moktan et al., 2008; Thitilertdecha et al., 2008). Recently, Org 27569 the interest in finding natural antioxidant agents with low cytotoxicity has increased significantly (Thitilertdecha et al., 2008). Several studies have focused on plant compounds (Teow et al., 2007; Erkan et al., 2008). However, only a few reports have been conducted on the antioxidant power of microbial extracts (Moktan et al., 2008). In previous studies, we described the production of several antimicrobial compounds by a newly identified B. subtilis B38 strain (Tabbene et al., 2009a) as well as their optimization (Tabbene et al., 2009b).