Inhibition Mechanisms Of Epicatechin Gallate Combined With Chitosan On MRSA And The Effects On Pork Preservation

MRSA was discovered in 1961.It has developed resistantance to almost all?-lactam antibiotics and is a superbug that has attracted much attention.In recent years,MRSA has been found and isolated from more and more foods.MRSA-contaminated food has posed a great threat to human health and also caused huge economic losses.In this paper,the synergistic bacteriostatic effects of 8 natural plant products and 5 commonly used commercial food preservatives were studied,the bacteriostatic mechanism of MRSA was explored,and the combination of natural plant products and commercial food was used for pork preservation,providing a new idea for the joint bacteriostatic and pork preservation research.The main research results are as following:(1)The Minimum inhibitory concentration of ECG and ?-polylysine were 625?g/m L and 39.06 ?g/m L,respectively.The combination of 1/8MIC ECG + 1/16 MIC chitosan had the best synergistic effect on the inhibition of MRSA,and the Fractional Inhibitory Concentration was 0.19.(2)ECG makes MRSA surface shrink nd middle sag;Chitosan can cuase MRSA irregular shape,blurred cell boundary,and adhesion between cells.Combined inhibition of the two bacteria can destroy the morphology of MRSA cells,causing MRSA cells to rupture,adhesion and death.(3)There were 122 differential genes of synergistic inhibition between ECG and chitosan,and their functions were mainly related to Redox,peptide synthesis,metabolism,aminoacylation,organic synthesis,etc.The different metabolic pathways were mainly citric acid cycle,carbon metabolism and ribosome.(4)The molecular mechanisms of sybergistic inhibition of ECG and chitosan were as follows: down-regulating arg G expression affecting amino acid metabolism,and reducing ATP content in MRSA cells;the down-regulation of clf A and ica A affected the formation and adhesion of MRSA biofilm.Up-regulated bla1,inhibited the synthesis of ?-lactamase and the expression of mec A.lyt M and lrg B were up-regulated,which damaged MRSA cell wall and promoted biofilm lysis and cell lysis death.(5)ECG and chitosan can effectively inhibit the growth and reproduction of MRSA in pork.The storage time of pork at 4 ? can be extended by 2 days,and the spoilage of pork can be delayed at 25 ?.Both ECG and chitosan could reduce myoglobin content,inhibit lipid oxidation,reduce free fatty acid content and maintain pork texture quality.Combined use of the two is more effective,and the dosage is reduced to 1/8 and 1/16 of the original,respectively.