Photocatalytic and Antibacterial Studies on Poly(Hydroxybutyrate-co-Hydroxyhexanoate) / Titanium Dioxide Composites

Abstract

Various microorganisms such as bacteria and viruses have been responsible for the rise in food poisoning outbreaks in numerous settings. To prevent this from happening, antimicrobial films can be used as packaging material or coatings on surfaces where food is being processed. However, films like these should not only be effective but also safe. Titanium dioxide (TiO2) when irradiated with ultraviolet light produces free radicals that can destroy organic contaminants and kill bacteria. TiO2 is approved by the U.S. Food and Drug Administration and the U.S. Pharmacopeia as a food and pharmaceutical colorant. Polyhydroxybutyrate is a bio-based polymer produced by certain bacteria. Blends of this polymer are being studied for use in implants and drug delivery. Hence, TiO2 immobilized to blends of this polymer may be suitable for use in food processing. Poly(hydroxybutyrate-co-hydroxyhexanoate) and titanium oxide (PHB-HH/TiO2) composite films were irradiated under fluorescent and blacklight lamps. The results show that these films can be activated by both lamps. However, the photocatalytic activity is higher when exposed to blacklight. The films were also irradiated in the presence of Escherichia coli and Staphylococcus aureus. Both bacteria had a 0 log count when a 3% PHB-HH/TiO2 composite film was exposed to blacklight for 5 h. Exposure to fluorescent light under the same conditions also showed some antibacterial activity. The photocatalytic activity of the films was enough to inhibit bacterial growth even when exposed to fluorescent lamps. PHB-HH/TiO2 composite films have photocatalytic and antibacterial properties when exposed to both fluorescent and blacklight lamps. The films can therefore be used in the food industry.