Protein-based plastics and their potential use in medical and food packaging applications
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The use of conventional plastics in medical and food packaging applications is ubiquitous, as the ability of a lightweight material that is able to withstand the stresses of application is paramount. However, the use of these materials comes with many drawbacks, such as the lack of biodegradability of the polymers utilized, as well as the lack of antibacterial properties, causing the potential spread of disease, contamination of food, and the existence of plastics in landfills. In order to address these issues, we have examined proteins that could serve as a substitute to the traditional polymers that are utilized on the market today in medical and food packaging applications. The types of proteins we examined for potential use in such applications were albumin from hen egg white, whey protein isolate, edible soy protein, and zein protein from corn. Through our screening studies, we have identified albumin from hen egg white and zein from corn as two different types of protein that possess the mechanical, thermal, and antimicrobial properties that would be highly useful in these applications. After screening, we then conducted additional tests to determine if the addition of low density polyethylene (LDPE), a traditional polymer, will alter the biodegradation and drug elution properties of the resulting protein-based thermoplastic. After testing for susceptibility to biodegradation, we determined that plastics that contained higher levels of LDPE were less susceptible to degradation, while the addition of LDPE had no significant effect on the ability of the plastic to release a drug or food preservative. When albumin and zein are compared to LDPE for environmental impact based on a life cycle assessment, we find that the production of the biomass to be converted into plastic possesses a larger environmental impact than LDPE production. Based on the research conducted in these studies, it will be possible to further examine other types of proteins that can be utilized in plastic production, the use of more additives to enhance the properties of the resulting plastic, as well as determining ways to limit the environmental impact of plastic production, use, and disposal.