Studies On Antimicrobrial Mechanism Of ?-polylysine Aganist Spoilage Microorganism In Grass Carp

?-polylysine??-PL?has a good effect on delaying the quality deterioration of grass carp,due to safe?healthy and natural preservatives.In this paper,we choose4 representative spoilage bacterias:Streptococcus lactis?Brochothris thermosphacta?Shewanella putrefaciens and Pseudomonas aeruginosa.Preservative effect?cell membranes and intracellular substances were studied in order to explore the antimicrobrial mechanism of?-PL aganist spoilage microorganism in cold-fresh grass carp.The preservative effect of?-PL to 4 spoilage bacterias indicated that Streptococcus lactis had the highest sensitive degree,then Brochothris thermosphacta?Shewanella putrefaciens and Pseudomonas aeruginosa in turn,and the MIC were 20?40?80?160?g/mL respectively;The diameters of inhibition zones of 4 spoilage bacterias became bigger with the increase of?-PL concentration,,indicating that?-PL had a significant preservative effect against spoilage bacteria.Surface hydrophobicity?cell membrane permeability?membrane protein?leakage of ion and cell morphology were multi-perspective studied to analyse the effect of?-PL on 4 spoilage bacterias cell membranes.The results showed that?-PL could increase cell surface hydrophobicity 1-2 times,increase cell membrane permeability,disrupt cell ion channel,leading to the leakage of Ca²⁺?K⁺?Mg²⁺.At the same time,?-PL hinderred the synthesis of molecular weight greater than 38 kDa or accelerated its'degrade,damaged normal cell membrane to holes,and eventually destroyed the cell membrane barrier,thus the growth of spoilage bacteria were inhibited.The effect of?-PL on spoilage bacteria cells studied by detecting of important enzymes?changes of the intracellular proteins content?the activities and the content of DNA,also the structure of cell by STEM.The result showed that?-PL influenced the enzyme activity seriously,damaged the deactivation of repiratory chain dehydrogensae,and?-glycosidase and Alkline Phosphatase?AKP?were in disorder phenomenon,finally leading to content increased.At the same time,by interferring the cell normal physiological activities,?-PL hinderred the macromolecular protein bilsynthesis or accelerated decomposition.Also by interfering with the normal synthesis of DNA,damaged cells DNA instructure,inhibiting the normal growth of spoilage bacteria.STEM showed that?-PL can destroy normal cell instructure,and then change the intracellular substances.Therefore,growths of spoilage bacteria were inhibited and even to death.