Submitted to: Journal of Applied Polymer Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/4/2009
Publication Date: 7/5/2010
Citation: Liu, L.S., Jin, Z.T., Coffin, D.R., Liu, C., Hicks, K.B. 2010. Poly (lactic acid) membranes containing bacteriocins and EDTA for inhibition of the surface growth of gram-negative bacteria. Journal of Applied Polymer Science. 117(1):486-492.
Interpretive Summary: About half of the world’s foods are wasted because of lack of effective packaging and preservation methods. Currently, 99% of packaging materials are made from petroleum - derived thermoplastics. These materials only provide a physical barrier between the foods and the environment, thus are insufficient to protect foods from fast deterioration. Furthermore, the use of large volumes of these materials has raised a big environmental concern, since they are not biodegradable. In this study, “active” packaging materials were prepared from the combination of two anti-bacterial products bacteriocins and a chemical, EDTA. These products were incorporated into packaging material made with poly (lactic acid), a biobased environmentally friendly polymer. The resultant new packaging materials actively inhibit/suppress the growth of a wide spectrum of bacteria from Gram-positive to negative, possess mechanical properties comparable to petroleum-derived thermoplastics, and degrade to non-toxic compounds in landfills, showing potential as a new generation of packaging materials. Makers of packaging films, food producers and crop growers will all benefit from this study.
Technical Abstract: Membranes containing antibacterial reagents, ethylenediamine-tetraacetic acid disodium salt (EDTA) and Nisaplin®, were produced by co-extrusion with poly (lactic acid) in the presence of a pharmaceutical grade glycerol triacetate. The incorporation of EDTA- Nisaplin® particles resulted in a heterogeneous biphasic structure, as revealed by scanning electronic microscopy, confocal laser microscopy, and acoustic emission tests. The inclusion of glycerol triacetate reduced the Young’s modulus and tensile strength, while enhancing the flexibility and the toughness of the resulting blends. The inclusion of the plasticizer also allowed the extrusion to occur at a temperature as low as 120 deg C to maintain the biological activity of Nisaplin®, which in combination with EDTA, plays a synergetic effect on suppression of the growth of Gram-negative bacteria, E. Coli O157:H7. The membranes thus obtained show their potential as packaging materials with a wide spectrum of antimicrobial activity.