NYSIN AS A BIOACTIVE COMPOUND EMBEDDED INTO BIODEGRADABLE FILMS FOR THE PRODUCTION OF ANTIMICROBIAL PACKAGING

Presentation: Oral (X) Poster (x)
Antimicrobial Packaging interacts either with the food or with the food’s headspace to reduce, inhibit or retard the microorganisms’ growth on food surfaces. Nysin bioactive compound can be embedded into natural polymers to produce antimicrobial biodegradable active films. Nysin is a bacteriocin produced by Lactococcus lactis that presents antimicrobial activity against a broad spectrum of Gram-positive bacteria. Poly(vinyl)alcohol (PVOH) is a biodegradable material that exhibits excellent optical and physical properties. However, PVOH is relatively expensive and displays a low biodegradation rate. PVOH films are often modified by the addition of other compounds, such as starch, and cellulose nano-crystals in order to reduce cost and to enhance PVOH films' eco-friendliness and performance. Starch has been used to replace synthetic polymers because it is widely available and very cheap. Another substances, the Maleic anhydride, has been used as a compatibilizer compound. A compatibilizer is able to interact with chemically soluble species in another phase, making the copolymers miscible between themselves. For this reason, Starch-PVOH-biodegradable-film blends were produced by the incorporation of cellulose nano-crystals as reinforcement particles, anhydride maleic as compatibilizer compounds, and nysin as antimicrobial substances. Starch-PVOH solution was prepared by the addition of water (7:3 w/w), and of glycerol 20% as the plasticizer polymer. Different concentrations of Maleic anhydride, cellulose-nanoparticles and Nysin were added into Starch-PVOH films, as defined by the Central Composite Rotational Design. Response surface methodology was performed in some cases, and in other cases the data was submitted to analysis of variance, followed by Tukey’s test at 5% of probability level, performed by the SAS software. The films’ mechanical properties were determined in the Instron testing machine model 3367, according to the ASTM D882-12. Samples were previously stored at 23 °C ± 2 °C and 50% ± 2% relative humidity for 24 h. The films’ maximum load (ML) was influenced by the presence of Maleic anhydride (A) and cellulose-nanoparticles (B) and their interaction, as shown by the equation ML=6.45A2+7.36AB+2.30A-8.13B+64.94. The films’ elongation at break (EB) was influenced only by cellulose-nanoparticles as shown by the equation: EB=3.20B2-0.70B+10.40. The media films’ thickness of 194 µm + 0.02 µm was determined using a digital micrometer (ID-C112XB, 0.001-mm, Japan). Antimicrobial activity against the foodborne pathogens Listeria monocytogenes and Staphylococcus aureus were measured by the vapor phase diffusion agar method in Mueller-Hinton (BD, New Jerswey, EUA) for 24 h at 37 °C ± 2 °C. The inhibition zone was 2.41 cm + 0.30 cm for L. monocytogenes and 2.52 + 0.54 for S. aureus, regardless of the films’ treatment. The Starch-PVOH-biodegradable films presented antimicrobial activity against the foodborne bacteria working for Gram-positive bacteria, indicating that the nysin biocompound has potential to produce antimicrobial active packagings. Beside that, the film was produced using a biodegradable matrix showing good mechanical properties influenced by cellulose nanocrystal and maleic anhydride addition, and their interaction.