| People eat food contaminated by pathogenic bacteria,which can lead to food poisoning,bacteremia,and meningitis,seriously threatening life and health.Chitooligosaccharides is a new food raw material with abundant sources with excellent broad-spectrum antibacterial properties.It can be used as a safe and non-toxic natural preservative to replace chemical preservatives and antibiotics in the food industry to reduce toxicity to the human body and the resistance of pathogenic bacteria.At present,there are many studies on the antibacterial activity of chitooligosaccharides.However,the structure and mechanism of chitooligosaccharides that exert antibacterial activity are still unclear,and the cost of chitooligosaccharides is higher than that of chemical preservatives.Because of the above problems,based on chitooligosaccharides with different structures,this study screened the type of chitooligosaccharides with the best antibacterial activity.It explored the differences in the antibacterial mechanism of chitooligosaccharides with different structures.At the same time,chitooligosaccharides were combined with natural substances to study their synergistic bacteriostatic effect and preliminarily explore the mechanism of synergistic effect to reduce production costs and provide new ideas for the development of natural food preservatives and bacteriostatic agents.The main survey results are summarized as follows:1.Chitooligosaccharides with the best antibacterial activity were screened,and the antibacterial mechanism of chitooligosaccharides with different structures was analyzed. Their inhibitory effects on Gram-positive and Gram-negative bacteria were evaluated,starting with chitooligosaccharides with different structures.HCOS with the best antibacterial effect and the most comprehensive antibacterial range was screened from chitooligosaccharides with different structures.The antibacterial mechanism of different molecular weight chitooligosaccharides was preliminarily explored.LCOS mainly destroyed the complete structure of the strain and made intracellular proteins,nucleic acids,ATP,and other substances outflow to achieve an antibacterial effect.HCOS affected the typical exchange of nutrients and metabolic waste by covering the surface of pathogenic bacteria.2.Chitooligosaccharides can replace chemical preservatives to play a bacteriostatic role.By comparing the bacteriostatic effect of HCOS with common food preservatives,it was found that HCOS had a lower bacteriostatic concentration than potassium sorbate and a broader bacteriostatic spectrum than nisin.The HCOS natural compound formula was further applied to preserve fish fillets.It was found that it could play a better effect under different storage temperature conditions than commercially available chemical preservatives.The shelf life of fish fillets could be extended by 3 days at 4°C,the shelf life was longer at-2°C and -18°C,and the quality of fish fillets was also improved.3.Chitooligosaccharides combined with plant essential oil or spirulina can significantly enhance antibacterial activity.The combination of 0.2 mg·m L-1HCOS and 0.1μL·m L-1 carvacrol essential oil can achieve the same bacteriostatic effect as 5μg·m L-1amoxicillin and50μg·m L-1 florfenicol,which can significantly improve the bacteriostatic effect.At the same time,the cost is similar to that of antibiotics to realize the substitution of antibiotics. Pathogenic bacteria usually exist on the surface of food and food production and processing equipment in the form of biofilm.It was found that the complex penetrates the biofilm by constructing a complex of HCOS and natural food raw material spirulina.HCOS wraps the pathogenic bacteria and binds spirulina to release reactive oxygen species,realizing the inhibition of bacterial and fungal biofilms,increasing the inhibition rate by 1-5 times,and further broadening the application prospect of chitooligosaccharides in the field of food preservation and bacteriostasis. |
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