Studies on antibacterial activity and antibacterial mechanism of a novel polysaccharide from Streptomyces virginia H03

A novel polysaccharide isolated from the broth of Streptomyces virginia H03 exhibited strong antibacterial activities on food spoilage and food poisoning microorganisms such as Staphylococcus aureus, Bacillus subtilis, Listeria monocytogenes, Escherichia coli, Zygosaccharomyces bailii and Candida utilis. The minimal inhibitory concentrations of the polysaccharide determined by the double broth dilution method were 15.6, 31.3, 31.3, 31.3, 125 and 125 (μg/ml) against the microorganisms mentioned above, respectively. The possible targets of the polysaccharide in bacteria might be cell wall, cytoplasmic membrane and DNA as indicated by electron microscopy, leakage of protein, cytoplasmic membrane permeability and DNA binding, respectively. Moreover, the antibacterial activity remained unchanged after being treated at 100 °C for 10 min, which indicated that the polysaccharide had a good heat-stability. In addition, it was safe according to mouse toxicity. All of these suggested that the polysaccharide might be used as a potential antimicrobial in food.