Study On The Influencing Factors Of ?-polylysine Antibacterial Activity And Its Antibacterial Membrane

?-polylysine(also known as?-PL)is an effective and safe natural preservative.Its chemical nature is an active peptide.?-PL not only has excellent antibacterial activity,but also shows a very good development prospect.At present,the research on?-PL has been relatively mature.The research and reports on the selection of high-yield strains,improvement and optimization of fermentation conditions,exploration of its synthesis mechanism,metabolic pathway after entering human body and its practical application in food have been more in-depth.However,how the antibacterial activity of?-polylysine is affected by food processing conditions or food matrix components has rarely been studied.On the other hand,whether?-polylysine can be used in combination with other antibacterial ingredients to reduce its use,expanding its antibacterial spectrum and application scope is still a question which is need to be discussed.In view of the above problems,this paper explores the change of the antibacterial activity of?-polylysine under different food processing conditions,and looks for the best action conditions and antibacterial mechanism of?-polylysine,and develops edible film with antibacterial activity by combining with Zn²⁺or natamycin,so as to broaden its antibacterial spectrum and application scope,and provide theoretical support for better application of natamycin in food industry support.The results are as follows:1.Escherichia coli and Staphylococcus aureus were used as test bacteria.The MIC and MBC of?-polylysine against the two bacteria were 162 mg/L and 651 mg/L respectively.The growth curve showed that the control group reached the logarithmic growth period at the 4th hour,but there was no significant logarithmic period and no significant increase in the number of bacteria.2.There was no significant difference in the antibacterial activity of?-polylysine treated at 4?,20?,40?,60?,80?,100?and 121?for 30 min.At different p H values(p H=4,5,6,7,8,9),?-polylysine showed different antibacterial activities to two kinds of tested bacteria:the inhibition rate of?-polylysine to the tested bacteria under acid condition was better than that under alkaline condition,and the inhibition rate reached the maximum value at p H=5.When?-polylysine is compounded with Zn²⁺and Mn²⁺,there is obvious synergistic antibacterial effect.When it is compounded with K⁺and Ca²⁺,there is no synergistic effect,while Mg²⁺can counteract the antibacterial effect of?-polylysine and has antagonistic antibacterial effected.3.Alkaline phosphatase(AKP)can be detected in the extracellular of the two kinds of bacteria used in this project after the antibacterial treatment of?-polylysine and its mixture,and the amount of AKP spillover gradually increases with the increase of the action time,indicating that the integrity of the cell wall is damaged,and the extent of the damage of the cell wall increases with the increase of time;The absorption rate of bacteria to crystal violet increased,the intracellular ATP of corresponding bacteria decreased significantly,while the extracellular ATP increased significantly.4.When?-polylysine is combined with natamycin,the antibacterial spectrum and effect of?-polylysine can be expanded;when zinc sulfate is combined with?-polylysine,the use of?-polylysine can be effectively reduced,but the antibacterial activity will not be weakened.Compared with the basic membrane,the surface of zinc sulfate-?-polylysine composite antibacterial membrane and natamycin-?-polylysine composite antibacterial membrane is smoother,and the thickness is not significantly changed,both within the range of 0.0976-0.0978 mm.However,the brightness of the antibacterial film decreased,the color gradually turned yellow and green,the moisture permeability of water vapor decreased,the tensile strength and elongation at break increased,indicating that the antibacterial film has a better toughness,can effectively prevent the water overflow in the food,is more convenient to use and is conducive to the preservation of the food.In conclusion,the antibacterial activity of?-polylysine is still affected by the p H of food processing and metal ions,in which Zn²⁺can enhance the antibacterial activity of?-polylysine.The film prepared by the combination of the two methods not only has a great improvement in physical properties,but also reduces the dosage of?-polylysine under the condition of constant antibacterial properties,which provides data support for broadening the range of use of?-polylysine.