The Action Mechanism On Phospholipid Membrane And Application Of Antimicrobial Peptide F1 Produced By Lactobacillus Paracasei FX-6

Antibacterial peptide had different antibacterial mechanism from traditional antibiotics,not easy to make the bacteria resistant,could be applied in biomedical,food preservation and other fields.In this laboratory prophase research,antibacterial peptide F1 were isolated from Lactobacillus paracasei FX-6 fermentation extracts,which was broad-spectrum,efficient,and stable antibacterial activity.And the antibacterial mechanism of F1 had made an elementary research.This paper researched on phospholipid membrane extracted from E.coli and S.aureus phospholipids or synthetic phospholipids,preparation of liposomes model and phospholipid bilayer model were prepared to research the strength and function of action between peptide and membrane.Studied by molecular dynamics simulation of F1 molecules on the phospholipid bilayer configuration change trend and the change of energy,and sports a detailed calculation,combined with the experimental data to further analysis the mechanism of F1.Then FX-6 production of antimicrobial peptides used in litchi at room temperature preservation,studies its application in fruits preservation of antimicrobial peptides,again through the FX-6 inoculation to the defatted soybean fermentation medium,expand the application scope of FX-6 strains,reduce the production cost of this extracts.The specific research contents are as follows:(1)Studied on the strength and mechanism of F1 acting on phospholipid membrane.F1 could be applied to phospholipid extracted from bacteria and artificially prepared,and the strength is related to the type of phospholipid molecules,the effects on membrane phospholipid liposomes composed of bacteria is stronger,and the effects were weak on that composed of animal cell membranes.This would be associated with its strong antibacterial activity and the characteristics of security.By phospholipids spreading into solid support Lipid Bilayer(SLB),using quartzcrystalmicrobalance with dissipation(QCM-D)for real-time monitoring of the role of F1 process,the results show that the role of F1 of phospholipid membrane effects were related to its concentration.Main show of low concentration of F1 was adsorpting.And high concentrations of F1 caused a decline in the quality of the film,increase of viscoelasticity,and damage of phospholipids membrane.(2)Molecular dynamics simulation of F1 and phospholipid bilayer effects.Molecular Dynamics simulation of F1 was carried out in the CHARMM field through the NAMD(NAnoscale Molecular Dynamics).F1 was placed in the buffer and two different molecular layers of phospholipid bilayer surface layer,and the three conditions were compared and analyzed.During simulation,movement of F1 was high degree in freedom in buffer,the spiral structure of the peptide chain proportion tended to reduce,the F1 in lipid bilayer surface would tend to be close to the membrane surface.Its n-terminal and membrane surface contacted each other,and F1 had a posture to insert.The RMSD value decreased,SASA value rised,and F1 peptide part of the formation of hydrogen bonds between amino acid and phospholipid membrane,such as van der waals energy in the system changed significantly at the same time.(3)Influence of the antibacterial peptides crude extracts of FX-6 on the storage quality of litchi.The harvested litchi fruit were treated by different concentrations of extracts.Found that could effectively inhibit microbial growth on the surface of the litchi,prevent mildew,increase healthy-fruit rate,of which,1.0 mg/mL of antibacterial peptides crude extracts fruit storage and processing group 6 days,healthy-fruit rate remained higher than 60%,which was better than sportak.At the same time,the crude extracts could inhibit the growth of the skin microorganism,reduce the pH value of the skin,inhibit the related enzyme activity,and effectively prevent the Browning of litchis peel.(4)Fermentation application of FX-6 strains.This study inoculated FX-6 into the defatted soybean milk to ferment,the results showed that the fermented extracts had strong antibacterial effects on several common food spoilage organisms such as E.coli.The optimum fermentation conditions were follow: defatted soybean concentration of 80 g/L,adding 2% glucose,initial pH 5,32 ? fermentation for 5 days.The test results showed that the active substances in the fermentation also included antibacterial peptide F1 and antibacterial substance F,and the purity was higher than that of the original milk fermentation.It is shown that the defatted soybean meal can also be used as the fermentation medium of fx-6 antibacterial peptide,and the application efficiency of fx-6 antibacterial peptide is improved.