Preparation And Study Of Immobilized Lysozyme Antibacterial Materials

Bacterial microbial infections have been a pressing problem in food and drug,biomedical and other research fields.Lysozyme,as a natural green antimicrobial agent,has a wide range of application prospects in food and medical care,etc.Immobilized enzyme technology is a way to immobilize enzymes into carrier materials using various physicochemical means,which can improve the enzyme activity and stability.Immobilized enzymes are easy to control and recyclable,and can play an important role in environmental protection,biomedicine and other aspects.In order to prepare better immobilized lysozyme antibacterial film,lysozyme was immobilized on two types of carriers,polyethylene(PE)and polyvinyl alcohol(PVA),and the immobilized lysozyme polyethylene(PE-LYS)film was obtained by covalent immobilization of the enzyme,and the combination of covalent linkage and physical adsorption was used.The immobilized lysozyme polyvinyl alcohol(PVA-LYS)film was obtained,and the PVA-LYS film with better antibacterial effect was applied to the preservation of semi-dried fish meat.The following results were obtained:(1)PE-LYS film was obtained by immobilizing lysozyme(LYS)onto polyethylene film by covalent linkage in an optimal process.The results showed that the immobilized lysozyme was more stable than the free lysozyme,and the inhibition rates of free and immobilized lysozyme were 47.3% and 69.9%,respectively,when both were incubated at a temperature of50°C for 180 min.The effect of oxidation temperature of PE surface on the mechanical properties of PE-LYS film was investigated.The results showed that the oxidation temperature increased the surface carboxyl content but decreased its mechanical properties,and the tensile strength and elongation at break of PE film decreased by 53.4% and 67.3%,respectively,when the temperature was increased from 65 to 90 °C.The attachment of fine LYS particles to the surface was observed by SEM,while IR spectra and XPS light also demonstrated that LYS was immobilized onto the PE surface.(2)Lysozyme was immobilized onto the PVA film by a combination of covalent linkage and physical adsorption.With the increase of LYS addition,the antibacterial effect of PVA-LYS film increased continuously,and the inhibition rate of Staphylococcus aureus reached 97.03%when the lysozyme addition was 5%.With the increase of LYS addition,the mechanical properties,gas barrier properties,and optical properties of PVA-LYS film decreased to some extent,and its hydrophobic angle first increased and then decreased.the thermal stability of PVA-LYS film was increased by the influence of LYS covalent linkage.The immobilization of LYS onto the PVA film was demonstrated by IR spectroscopy,XRD and microscopic morphology.(3)Considering the mechanical properties and antibacterial effect of PVA-LYS film,the PVA-LYS film with 2% lysozyme addition was selected to be applied on the freshness study of semi-dried fish meat,and the results showed that all the indexes of the compared PE films reflected that the PVA-LYS film had good freshness effect.The freshness of total bacterial colony and TVB-N as the standard,PVA-LYS film could extend the shelf life of semi-dried fish meat under refrigeration condition of 2～8℃ by 4～6 days compared with the control PE film.Moreover,PVA-LYS film retarded the change of TBA and p H value of semi-dried fish meat,so PVA-LYS film is a good antimicrobial packaging material.