Lifespan and bioactivity improvement of bacteriophages immobilized on carboxymethylcellulose - Cationic starch-coated paper for food packaging

Bacteriophages (phages) have a great potential to target specifically foodborne bacterial pathogens, particularly in packaging materials. However, incorporating phages into packaging surfaces requires stabilizing their structure and maintaining their infectivity during the papermaking process. In this study, several coating formulations containing various ratios of carboxymethyl cellulose, cationic starch, and glycerol were applied to a base paper to assess phage stability. The anti-Listeria phage preparation LISTEX™ P100 was applied to the coated paper surface and then dried under a laminar airflow. Physical analyses of the base paper modifications were carried out and water absorption properties of the various coatings were analyzed. As the humidity level is also a critical factor for maintaining phage activity, the coated papers were stored at various relative humidity levels. The most effective coating for maintaining phage activity contained 2 % carboxymethylcellulose, 2 % cationic starch, and 5 % glycerol. The coated phage-containing paper was 16 μm thin, optically identical to base paper but heavier in grammage (15 % increase). The phage titers on the surface of the coating were maintained at 10⁴ PFU/cm² for 14 days when stored at 4 °C with 75 % relative humidity.