Preservation Effect On Chicken Meat And Antibacterial Mechanism Of Antibacterial Peptide Produced By Lactobacillus.paracasei Fx-6

In the early stage of the laboratory,a strain of Lactobacillus paracasei FX-6 was isolated from the fermented milk of Tibet Kefir,which could ferment milk producing antibacterial peptide.The fermentation product has the advantages of wide antibacterial spectrum and natural non-toxic side effects.In this paper,the crude extract of the antibacterial peptide produced by the fermented milk was used to study the preservation effect on chicken meat.The physical and chemical indicators,sensory evaluation and microbial indicators were used to evaluate the quality during storage;High-throughput sequencing technology was used to analyze flora changes during storage,and the changes of the dominant spoilage bacteria compared the group dealed with antibacterial peptide with the blank group,and determine whether the crude extract of the antibacterial peptide inhibit the spoilage bacteria or not;Finally,the dominant spoilage bacteria were isolated and purified from the corrupted chicken,and the antibacterial peptide crude extract was used to study the antibacterial mechanism on Pseudomonas and Serratia.Subsequently,the antibacterial peptide crude extract was used as an antibacterial agent added to the gelatin film to prepare the antibacterial film to expand the application of the antimicrobial peptide crude extract.The main findings of this paper are as follows:1.The preservation effect of different concentrations of antimicrobial peptides crude extracts on chicken meat was studied.The results showed that the crude extract of antimicrobial peptides could reduce the p H,TVB-N value and total number of colonies of chicken during storage.It is also conducive to the maintenance of the sensory quality of chicken.Compared with the blank group,it can prolong the shelf life of chicken stored at 4 ? for about 4 days.2.There were significant differences in volatile organic compound(VOC)was found between the control and test group with 100 mg/m L antimicrobial substance by HS-GC-IMS.The results also showed that the antimicrobial substance could inhibit the generation of bad odour.3.High-throughput sequencing was used to study the changes in flora during chicken storage.The study found that at the level of the family,the 0th day of the blank group was mainly Proteobacteria(76.9%),Firmicutes(10.5%),Bacteroidetes(7.4%),Actinobacteria(3.3%);Proteobacteria(99.4%),Firmicutes(0.5%)on the 8th day of the blank group;Proteobacteria(81.4%),Firmicutes(10.2%),Bacteroidetes(5.9%),Actinobacteria(1.2%)on the 8th day of the crude extract of the antimicrobial peptide,which indicate that the crude extract of antimicrobial peptide can significantly inhibit the growth of Proteobacteria.At the genus level,the blank group chicken(0 d)mainly consisted of Citrobacter(24.3%),Acinetobacter(14.3%),Enhydrobacter(14%),Pseudocitrobacter(4.7%),HafniaObesumbacterium(3.8%),Pseudomonas(3%),Lactobacillus(2.9%),Aeromonas(2.5%)and Raululella(2.3%)and the other.In the blank group of chickens(8 d),the flora structure changed greatly,Pseudomonas(89.7%),Hafnia-Obesumbacterium(3.1%),Serratia(2.6%),Citrobacter(1.4%)and Acinetobacter(1%),Lactobacillus and Empedobacter disappeared,of which Pseudomonas and Serratia is a typical chicken spoilage organism that has been reported.On the 8th day,the bacterial group of the antibacterial peptide crude extract treatment group became Pseudomonas(63.1%),Lactobacillus(7.3%),Empedobacter(2.2%),Hafnia-Obesumbacterium(1.3%),Acinetobacter(1.2%),Citrobacter(1.4%)and Serratia(0.7%).The crude antibacterial peptide extract can significantly inhibit the dominant spoilage bacteria Pseudomonas and Serratia in chicken,which may be the main reason that the crude extract of antibacterial peptide can significantly prolong the shelf life of chicken.4.The antibacterial mechanism of the crude antibacterial peptide extracts against Pseudomonas and Serratia was studed.The minimum inhibitory concentrations of crude antibacterial peptide extracts against Pseudomonas and Serratia were 12.5 mg/m L and 6.25 mg/m L,respectively.Subsequently,it was confirmed by potassium ion leakage,cell membrane permeability,protein leakage in bacterial liquid and other experiments that the crude extract of the antimicrobial peptide can cause changes in cell membrane permeability to allow the crude extract of the antimicrobial peptide to enter the cell membrane.The crude extract of antibacterial peptide can inhibit the synthesis of certain proteins in the cells by SDS-PAGE electrophoresis.The crude antibacterial peptide extract can be combined with the DNA of Pseudomonas and Serratia by DNA block experiments.DNA bands are blocked,and decomposed.5.The crude extract of antibacterial peptide was used as an antibacterial agent to prepare an antibacterial film.In this section,the effects of different amounts of antibacterial crude extracts on the performance of antibacterial membranes were investigated.The results showed that the gelatin composite membrane with the crude extract of the antimicrobial peptide was significantly increased in the ultraviolet wavelength range.The addition of the crude extract of the antimicrobial peptide caused the color of the membrane to be yellowish.When 50 mg/m L of the crude extract of the antimicrobial peptide was added to the gelatin film,the WVP was reduced slightly,and the mechanical properties are improved to some extent.The antibacterial ability of the film was more significant with the increasing the concentration of antimicrobial peptide.FTIR and SEM show good compatibility of the composite film.The DSC data showed that the crude extract of the antimicrobial peptide had a certain degree of reduction on the thermal stability of the composite membrane.It is indicated that the crude extract of antibacterial peptide can be used as an antibacterial agent to prepare an antibacterial film,which can expand the application of crude extract of antibacterial peptide.