Protein In Plastic: What's The Harmful Truth?

While there is no protein in plastic, plastic waste can be converted into edible protein powder. This is achieved by heating the plastic to break it down into its individual components, which are then fed to a specialized population of bacteria that will ingest it and grow. The resulting bacterial cells are composed of around 55% protein. This process could help address the issues of hunger and plastic pollution. However, there are challenges to implementing this technology on a wide scale, including regulatory hurdles and public perception.

Plastic waste converted to edible protein powder

Plastic is a significant contributor to climate change and pollution, with over 79% of the 6.3 billion tons of plastic produced annually ending up in landfills and oceans. This waste takes a minimum of ten years to break down, and often much longer, leading to a massive accumulation of plastic waste that has severe environmental consequences.

To address this issue, researchers at Michigan Tech University have developed a process to convert plastic waste into edible protein powder. The process, known as BioPROTEIN (Biological Plastic Reuse by Olefin and Ester Transforming Engineered Isolates and Natural Consortia), involves breaking down the long polymer chains of plastic using heat and a reactor. This process turns plastic into an oily compound composed of carbon, oxygen, and hydrogen.

This oily substance is then fed to oil-eating bacteria, which thrive on these elements and rapidly grow on this diet, producing more bacterial cells composed of roughly 55% protein. These bacterial cells are then dried out and turned into an edible protein powder. The entire process is currently performed on a lab bench, but the team aims to create a small box system that can take plastic and produce protein powder, with a goal of recovering 100 grams of protein powder through this system.

The development of this technology offers a potential solution to two prominent global issues: hunger and plastic pollution. By converting plastic waste into a valuable food source, this process can help address food shortages and malnutrition while also reducing the amount of plastic waste that ends up in landfills and oceans. This innovative approach highlights the potential for creative solutions to complex environmental challenges and underscores the importance of continued research and development in this area.

Potential solution to hunger and plastic pollution

Plastic is everywhere. It is in the food we eat, the water we drink, and even the air we breathe. While it is not feasible to get rid of plastic entirely, we can change our habits by reusing plastic products instead of throwing them away.

A team of scientists led by microbiologist Stephen Techtmann from Michigan Technological University has developed a process to convert plastic waste into edible protein powder. The process uses pyrolysis and fermentation, combined with a proprietary bacteria population. First, waste plastic is heated to high temperatures in the absence of oxygen to break it down into its individual components (pyrolysis). Then, the broken-down plastic, now an oil-like substance, is fed to a specialized population of bacteria that will ingest it and grow (fermentation). The resulting bacterial cells are composed of around 55% protein, and this protein-rich biomass can be used as food.

This process currently works on a lab bench, and Techtmann's initial goal is to deploy the system cheaply and easily in disaster areas or environments experiencing food shortages. If the process can be scaled up, it could become a widely available food source, helping to address the world's growing hunger problem. According to the United Nations, 690 million people, or 8.9% of the world's population, are hungry, and this number is expected to increase by 10 million people in one year and 60 million in five years.

However, there are challenges to implementing next-generation proteins on a wide scale. Regulatory hurdles, public perception, and concerns about purity and scalability need to be addressed. Nevertheless, with further development and optimization, the process of converting plastic waste into edible protein powder could be a potential solution to both hunger and plastic pollution.

Pyrolysis and fermentation process

Pyrolysis and fermentation are two processes that can be combined to convert plastic waste into edible protein. Pyrolysis is a chemical process that breaks down plastics into other molecules by heating them to extremely high temperatures in the absence of oxygen. The plastic is fed into a pyrolysis reactor, where it turns into oil, which can then be used to create new materials or fuels. The oil is then boiled and distilled in another vat, generating natural gases such as methane, ethane, butane, and propane. These gases can be captured and used as a source of energy to power the pyrolysis reactor or other industrial processes.

The fermentation step comes after the pyrolysis process. The oil-like substance resulting from the pyrolysis is fed to a specialized population of bacteria that will ingest it and grow. The resulting bacterial cells are composed of around 55% protein, and this protein-rich biomass can be used as food. This process is known as biomass fermentation, where the microbial biomass itself is used as a food ingredient.

The use of fermentation to create new protein sources is an exciting development in biotechnology. It offers an opportunity to deliver optimized nutrition and improved flavor or functionality, especially when incorporated with other food segments. Fermentation is a familiar method for producing food, which means it may gain faster regulatory approval and face less consumer resistance. However, there are still some drawbacks and challenges to be addressed. Overcoming regulatory hurdles to human consumption can be difficult and time-consuming, and marketing an edible product made from bacteria may be problematic as people may be hesitant to eat it. Additionally, ensuring the purity of the plastics broken down in the generator is crucial, and any potentially toxic byproducts must be eliminated or minimized.

Precision fermentation (PF), a relatively new field of biotechnology, has emerged as a promising source of additional protein. PF uses the same fundamental principles of traditional fermentation but with the added benefit of reprogramming microbes to produce specific, customized molecules that can serve as new food ingredients. By introducing the genetic information that codes for specific proteins into the microbial genome, cells can be programmed to act as highly efficient cellular factories that can grow on a variety of carbon sources and deliver desired outputs, typically proteins equivalent to those found in nature.

Bacteria's role in transforming plastic

The world is grappling with a plastic crisis. Only 9% of the plastic ever made has been recycled, with the rest ending up in landfills and waterways. This has led to an exponential increase in plastic waste, with over 12 million metric tonnes of plastic entering the ocean every year. The strength of polymers is what allows plastics to remain in the environment for an extended period. Natural processes can usually only break plastic into smaller pieces, unable to break polymer chains.

This is where bacteria come in. Bacteria play a crucial role in transforming plastic waste into something useful. The process of plastic biodegradation by bacteria involves several stages. Firstly, bacteria adhere to and erode the plastic surface. This is followed by the breakdown of plastic into smaller molecules through the action of enzymes. These enzymes, such as PET hydrolase, can change the polymer chain structure, enhancing the efficiency of enzymatic hydrolysis. The bacteria then absorb the smaller molecules, utilising them for growth and energy, and excreting the rest.

Several bacterial species have been identified as effective plastic degraders. One notable example is Ideonella sakaiensis, a bacterium discovered by Japanese scientists in a recycling plant in Sakai, Japan. I. sakaiensis has the unique ability to break down the bonds between monomers in a type of plastic called polyethylene terephthalate (PET), which is commonly used in water bottles and food packaging. The bacterium produces specific enzymes that enable it to metabolize PET, breaking it down into precursor molecules. These precursor molecules can then be used to create new plastic, bringing us closer to achieving infinitely recyclable plastic.

In addition to I. sakaiensis, other bacteria have been engineered to transform plastic waste. Researchers have developed a plastic-eating strain of Escherichia coli (E. coli) that can efficiently convert PET waste into valuable compounds like adipic acid, used in the production of nylon, drugs, and fragrances. By incorporating the genetic sequence for producing these enzymes into plasmids, which can replicate independently in cells, bacteria can be engineered to produce the desired enzymes and transform plastic waste.

While the discovery of plastic-eating bacteria offers promising solutions to the global plastic crisis, it is important to acknowledge that the process of plastic biodegradation is complex and limited in scope. It requires specific conditions and microbial species, and it does not address the vast amount of plastic waste already released into the environment. Nevertheless, the potential of bacteria in transforming plastic waste into valuable resources or recyclable materials presents a glimmer of hope in our quest for innovative solutions to tackle the world's plastic problem.

Plastic ingestion and metal concentration in birds

Plastic ingestion by birds is a significant environmental concern, with plastic waste and debris accumulating in various terrestrial and aquatic avian species. This issue has led to increased research efforts to understand the impacts of plastic ingestion on bird health and the potential consequences for ecosystems.

One study found that plastic ingestion by flesh-footed shearwaters (Puffinus carneipes) resulted in a positive correlation between the amount of ingested plastic and the concentration of chromium (Cr) and silver (Ag) in their fledgling breast feathers. This finding suggests that plastic ingestion may contribute to the accumulation of certain metals in birds' tissues.

Another study on the livers of two Pachyptila seabirds investigated the relationship between ingested plastic and metal concentrations. The results indicated a potential link between plastic consumption and increased levels of Cu and Zn in the liver. However, it is important to note that starvation and fasting can also influence metal(loid) concentrations in the body, making it challenging to isolate the direct impact of plastic ingestion on metal levels.

Additionally, plastic ingestion has been associated with negative health consequences in birds. For example, chicks of Japanese Quail with observed plastic ingestion experienced delayed sexual maturity and a higher incidence of epididymal intra-epithelial cysts in males. Ingestion of microplastics by adult short-tailed shearwaters (Ardenna tenuirostris) was also found to impact their chicks, potentially leading to reduced food intake, delayed ovulation, and increased mortality.

Furthermore, plastic ingestion can cause gastrointestinal obstructions in seabirds, leading to ulcerations in the gizzard or blockage of the pylorus, making feeding impossible and resulting in increased mortality. The obstruction of the gastrointestinal tract can also lead to a decrease in fat reserves, further exacerbating the health impacts of plastic ingestion.

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