Abstract
The continuing emergence and development of pathogenic microorganisms that are resistant to antibiotics constitute an increasing global concern, and the effort in new antimicrobials discovery will remain relevant until a lasting solution is found. A new bacterial strain, designated JFL21, was isolated from seafood and identified as B. amyloliquefaciens. The antimicrobial substance produced by B. amyloliquefaciens JFL21 showed low toxicity to most probiotics but exhibited strong antimicrobial activities against multidrug-resistant foodborne pathogens. The partially purified antimicrobial substance, Anti-JFL21, was characterized to be a multiple lipopeptides mixture comprising the families of surfactin, fengycin, and iturin. Compared with commercially available polymyxin B and Nisin, Anti-JFL21 not only could exhibit a wider and stronger antibacterial activity toward Gram-positive pathogens but also inhibit the growth of a majority of fungal pathogens. After further separation through gel filtration chromatography (GFC), the family of surfactin, fengycin, and iturin were obtained, respectively. The results of the antimicrobial test pointed out that only fengycin family presented marked antimicrobial properties against the indicators of L. monocytogenes, A. hydrophila, and C. gloeosporioides, which demonstrated that fengycins might play a major role in the antibacterial and antifungal activity of Anti-JFL21. Additionally, the current study also showed that the fengycins produced by B. amyloliquefaciens JFL21 not only maintained stable anti-Listeria activity over a broad pH and temperature range, but also remained active after treatment with ultraviolet sterilization, chemical reagents, and proteolytic enzymes. Therefore, the results of this study suggest the new strain and its antimicrobials are potentially useful in food preservation for the biological control of the multidrug-resistant foodborne pathogens.
Highlights
Foodborne diseases have been a serious global public health issue and most of them are caused by foodborne pathogens such as Salmonella, Shigella, Vibrio, Escherichia coli O157, Yersinia enterocolitica, Listeria monocytogenes, Staphylococcus aureus, and Aspergillus flavus, etc. (World Health Organization, 2015; European Food Safety Authority, 2018; Tack et al, 2019)
The negative controls did not show any antimicrobial ability against all the indicator strains, which suggest that the solvents itself did not affect the antimicrobial activity of the antibiotics against the tested indicator strains
The current study shows that the fengycins produced by B. amyloliquefaciens JFL21 maintained anti-Listeria activity over a broad pH and temperature range, but it was active after treatment with ultraviolet sterilization, chemical reagents, and proteolytic enzymes (Table 5)
Summary
Foodborne diseases have been a serious global public health issue and most of them are caused by foodborne pathogens such as Salmonella, Shigella, Vibrio, Escherichia coli O157, Yersinia enterocolitica, Listeria monocytogenes, Staphylococcus aureus, and Aspergillus flavus, etc. (World Health Organization, 2015; European Food Safety Authority, 2018; Tack et al, 2019). Many studies have shown that the cyclic lipopeptides (CLPs) produced by Bacillus spp. have potent antimicrobial activity against antibiotic-resistant strains and can be generally divided into three main families: surfactin, fengycin, and iturin (Chi et al, 2015; Jemil et al, 2017; Perez et al, 2017; Piewngam et al, 2018) Due to their specific amphiphilic structure, CLPs primarily destroy target organisms by directly disrupting the integrity of the plasma membrane or cell wall in a detergent-like manner, and display a lower propensity to develop resistance than do conventional antibiotics (Banat et al, 2010; Mandal et al, 2013; Singh and Abraham, 2014; Patel et al, 2015; Ndlovu et al, 2017). Because of these attractive characteristics, naturally produced antimicrobial CLPs have received increasing attention as promising new antibiotic candidates for food, pharmaceutical, and biomedical applications
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