# Selected Useful Properties of Polylactide Films Containing Nisaplin and Natamax  
[PERSON]  
1 Department of Genetics, Faculty of Biology and Veterinary Science, Nicolaus Copernicus University, Torun, Gagarina 11, 87-100 Torun, Poland; [EMAIL_ADDRESS]-pl (P.B. ); [EMAIL_ADDRESS] (ML.L)
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[PERSON]  
2 Department of Environmental Microbiology and Biotechnology, Faculty of Biological and Veterinary Sciences, Nicolaus Copernicus University, Torun, Gagarina 11, 87-100 Torun, Poland; [EMAIL_ADDRESS] (P.B. ); [EMAIL_ADDRESS] (ML.L)  
[PERSON]  
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[PERSON]  
1 Department of Genetics, Faculty of Biology and Veterinary Science, Nicolaus Copernicus University, Torun, Gagarina 11, 87-100 Torun, Poland; [EMAIL_ADDRESS] (P.B. ); [EMAIL_ADDRESS] (ML.L)  
[PERSON]  
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[PERSON]  
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Footnote 2: email: [EMAIL_ADDRESS]; [EMAIL_ADDRESS]; katarzyna. and vinyl acetate-ethylene copolymer [14]. Organic acids, bacteriocins, lysozyme, and essential oils are most often used to coat the packaging surface [15]. Packaging materials with antibacterial properties, obtained by physical adsorption of a biocide to the surface of the material, can be used for packaging food products. The condition for the effective operation of such packaging is its direct adhesion to the protected (fixed) product [16]. Another way to obtain bactericidal packaging is immobilization. It involves immobilizing a bactericidal substance on the surface of polymeric materials through covalent or ionic bonds. When using this method, the presence of functional groups in polymers and bactericidal substances is necessary. Immobilization of bactericidal substances can occur in two ways. The first one involves direct immobilization of the biocide on the polymer surface, the second one requires the presence of intermediate compounds. Binding agents may be dextrans, glutaraldehyde, ethylenediamine, or polyethyleneimine [17]. Positive bactericidal results (mainly against Gram-positive bacteria) are obtained in the case of immobilization of lysozyme, which becomes strongly bound to polyvinyl alcohol via glutaraldehyde. The use of packaging containing bactericidal substances, regardless of the method of introducing them or applying them to the polymer, leads to protection of food against the development of undesirable microorganisms, extending the shelf life of products, increasing health safety, reducing the possibility of microbiological infection, minimizing the development of microorganisms during transport and storage, and increasing effectiveness of preservation methods (i.e., packaging in a modified atmosphere, pressure preservation) of food products [16]. The bactericidal compounds introduced into the polymer matrix during processing must be resistant to high temperatures and have low volatility. There are also methods by which less resistant substances, including bacteriocins, can also be incorporated into polymers [14; 15; 16; 17]. Bactericons are ribosomally synthesized antimicrobial proteins (AMPs), most often used directly for food preservation [18]. Some of the best known bacteriocins are nisin (trade name Nisaplin\({}^{\circledR}\), Danisco, Denmark) and natamycin (Natamax, Danisco, Denmark), which have antimicrobial properties against pathogens of concern in the food industry [19; 20]. Nisin acts against vegetative forms of bacteria and can also effectively inactivate bacterial spores by altering their structure [21]. There have already been attempts to incorporate these substances into various matrices to produce food packaging materials. [PERSON] et al. [22] introduced nisin and natamycin into a chitosan matrix and obtained antimicrobial activity against seven species of bacteria and two species of fungi that are a problem in food production and storage.