Effect of antimicrobial peptide APNT-6 produced by Bacillus natto on fresh-keeping of Litopenaeus vannamei at low temperature

A new biological preservative—antimicrobial peptide APNT-6 produced by Bacillus natto NT-6 and purified by column chromatography will be applied in the fresh-keeping of Litopenaeus vannamei. Bacillus antimicrobial peptides are a series of lipopeptides substances produced by represented Bacillus strains of B. subtilis, B. amyloliquefaciens and B. natto, which include surfactin, iturin, fengycin, subtilin and so on. Numerous studies show that Bacillus antimicrobial peptides have a startling range of antimicrobial activities that can include action against most Gram-negative and Gram-positive bacteria, fungi, enveloped viruses, and eukaryotic parasites. Recently, our research group isolated a highly antibiotic activity and largely antimicrobial spectrum strain—B. natto NT-6 from the Chinese traditional food—lobster sauce. According to the mass spectrometry (ESI /MS /CID) analysis,we know the mainly antimicrobial substances produced by this strain is Bacillus antimicrobial peptides, mainly including surfactin, fengycin, and iturin(called after APNT-6). Through oral acute toxicity in mice we found that its LD50 greater than 5000 mg/kg body weight, indicating that antimicrobial peptide APNT-6 has high food safety. In this paper, the antibacterial activities of antimicrobial peptide on spoilage organisms were determined by Oxford cup assay. Then the quality changes of L. vannamei during storage at (4±1) ℃ were investigated, including the pH, total volatile basic nitrogen (TVB-N), aerobic plate count (APC) and sensory assessment. The results showed that antimicrobial peptide APNT-6 can effectively inhibit 8 strains of spoilage organisms isolated from L. vannamei. During storage at (4±1) ℃, with the extension of storage time, the gradually increasing values of pH, TVB-N and APC of L.vannamei were observed during the 7 days storage. However, incubated 0.5 mg/mL antimicrobial peptide can effectively slow down the value increasing, which extends the shelf-life of L. vannamei by 2-3 days.