The study, by Alexander Jones, Abhyuday Mandal, Suraj Sharma was two-fold; to find ways to reduce the amount of petroleum used in traditional plastic production and to find a fully biodegradable bioplastic.
Significant antibacterial properties
They tested three non-traditional bioplastic materials; albumin (egg whites), whey and soy proteins as alternatives to conventional petroleum-based plastics and found albumin-glycerol blended bioplastic met both standards because it has significant antibacterial properties.
Albumin, a protein found in egg whites, demonstrated antibacterial properties when blended with a traditional plasticizer such as glycerol.
“The proteins of albumin, soy, and whey provide possible sources of raw material for bioplastic production, as they have already been utilized in the area of edible films and low-stress applications,” said Jones.
“We conducted this study to investigate the thermal, viscoelastic, and antibacterial properties of the albumin, soy, and whey bioplastics with the use of three plasticizers—water, glycerol, and natural rubber latex (NRL).
“In terms of antibacterial activity, the albumin–glycerol and whey–glycerol were the best bioplastics, as no bacterial growth was observed on the plastics after 24 hours of inoculation.”
Contamination in food packaging
According to Jones, the research will help to scale up production of bioplastics for use in food packaging as well as biomedical applications.
He said in 2002, 4.5 out of every 100 hospital admissions led to a hospital-acquired infection in the US, with over 99,000 deaths and in a study by Gould, an outbreak of methicillin-resistant Staphylococcus aureus (MRSA) saw a doubling of the cost of a hospital visit, with an overall cost between $1.5bn and $4.5bn in the US annually.
Based on the findings by Alice Neely and Matthew Maley, both MRSA and vancomycin-resistant enterococci (VRE) were able to survive at least one day when inoculated onto the surface of materials commonly used in healthcare applications, with some microorganisms being able to survive for more than 90 days.
“It is because of these issues that materials that could provide antimicrobial properties are being examined for bio-medical applications, as that would help in containing or reducing the hospital-acquired infections,” added Jones.
“Another area in which contamination is a notable risk is the food packaging, where the material is in contact with food that will be consumed.”
According to a review study by Lau and Wang, there are five different aspects in which traditional plastics will contaminate food: the gradual degradation of the plastic that contains the food, volatiles such as benzene that are incorporated in the molecular structure of the plastic; contamination caused by the environment; contamination due to the processing agents used to produce the plastics; and other contaminants that are specific to the type of monomer utilized.
“Food contamination by traditional plastics is caused by the use of a polymer that was not incorporated in the food product itself, leading to the migration into the food,” said Jones.
“There are three interrelated stages that occur when food becomes contaminated by the plastic packaging: diffusion that occurs within the polymer, solvation of the migrant at the food–polymer interface, and the dispersion of the migrant into the bulk of the food product.
“To determine alternative materials such as proteins to be used in plastics, thermal and viscoelastic analysis must first be conducted to determine their suitability for the given application.”
Source: Department of Textiles, Merchandising & Interiors, University of Georgia, Athens, Georgia; Department of Statistics, University of Georgia, Athens, Georgia.
Publication: Journal of Applied Polymer Science: Volume 132, Issue 18, May 10, 2015
Title: Protein-based bioplastics and their antibacterial potential
Author(s): Alexander Jones, Abhyuday Mandal, Suraj Sharma.