Researchers recycle shrimp waste into supplements

The shells of crustaceans and wood waste could become nutritional supplements and medicine, with the help of a novel process developed by researchers from NUS.

A team led by Associate Professor Yan Ning and Assistant Professor Zhou Kang from NUS Chemical and Biomolecular Engineering​ have devised a method to turn shells from prawns and crabs into L-DOPA, a widely used drug to treat Parkinson's disease and they say a similar method can be used to convert wood waste to Proline, which is essential for the formation of healthy collagen and cartilage.

The global food processing industry generates as much as eight million tonnes of crustacean shell waste annually, including branches pruned from trees and sawdust from workshops. Deriving ways to upcycle these food and agricultural waste materials into useful compounds will reap benefits without straining landfills. 

Although reusing waste materials has gained traction in recent years, the typical output of chemicals produced from waste recycling is often less diversified than the conventional chemical synthesis pipeline which uses crude oil or gas. To overcome the limitations, the NUS researchers came up with a pathway that marries a chemical approach with a biological process. 

They first applied chemical processes to the waste materials and converted them into a substance that can be “digested” by microbes. The second step involves a biological process, akin to the fermentation of grapes into wine, where they engineered special strains of bacteria such as Escherichia coli to convert the substance produced in the chemical process into a higher value product such as amino acids. 

The NUS team took four years to derive their method and applied it to obtain high-value chemicals from renewable sources in a sustainable way.

Compared to conventional methods of producing amino acids which require sugars as the substrate, the novel method developed by the NUS researchers uses the abundant food and agricultural waste as the starting raw material, thereby cutting down cost

Producing organic chemicals cheaper and faster

Conventionally, L-DOPA is produced from L-tyrosine, a chemical made from fermenting sugars. With the approach developed by the NUS team, crustacean waste is first treated using a simple chemical step, allowing it to be used by microbes to produce L-DOPA.  The yield of the NUS method is similar to that achieved in the traditional method using sugars. In addition, compared to glucose, the most common sugar used, which costs between US$400 to US$600 per ton, shrimp waste costs only about US$100 per ton. Given the low cost and abundance of shell waste, the NUS team’s process has the potential to provide L-DOPA at a lower cost. 

Proline, on the other hand, is conventionally produced through pure biological processes. The NUS team’s unique method has now replaced most of the transformations by using chemical processes, which are much faster. As a result, the new integrated process could achieve higher productivity and potentially lead to reductions in capital investment and operating costs.

The research on producing amino acids such as L-DOPA from crustacean shells was first published online in the Proceedings of the National Academy of Sciences (PNAS) on 25 March 2020, while the work on producing Proline from wood waste was reported in Angewandte Chemie on 27 July 2020.

“Chemical processes are rapid and can utilise a variety of harsh conditions such as extreme heat or pressure to break down a wide variety of waste materials as no living organism are involved, but they can only produce simple substances. On the other hand, biological processes are a lot slower and require very specific conditions for the microbes to flourish but can produce complex substances which tend to be of higher value. By combining both chemical and biological processes, we can reap the benefits of both to create high-value materials,”​ explained Asst Prof Zhou.

Potential to upcycle other types of waste

The NUS team’s methodology has the potential to be applied to different types of waste materials, and they can tailor the process, based on the type of waste as well as the target end product. 

Moving forward, the team is looking to adapt their unique process to other forms of waste, such as carbon dioxide and wastepaper. Such development would reduce the society’s reliance on non-renewable resources for acquiring chemicals which are important constituents of many nutritional supplements and medicine today.

“Our novel chemical-biological integrated workflow offers a general pathway to produce a variety of high-value organonitrogen chemicals. While it may sound simple on paper to just combine two different methodologies, the devil is in the details. Given that these chemicals are found in a vast array of commercially valuable pharmaceuticals, pigments and nutrients, we are excited to expand our research and develop new methodologies to produce value-added chemicals from other abundant, locally available substrates found in Singapore,”​ shared Assoc Prof Yan.  

The research team is also planning to scale up the processes currently developed in their laboratories, and to work with industrial partners to commercialise this technology.

Sustainable developments

The issue of waste is a massive inspiration for innovation in the health and nutrition space today, with sustainability becoming a key purchase driver in the sector.

Earlier this week, NI reported​ that researchers released details of an intriguing new method to convert pig blood into a powder with 90% protein content that can be used as a supplement in a variety of foods.

The method uses an enzyme extracted from the papaya fruit to separate protein from pig blood. The enzyme can also be used to separate iron from the blood that can be used in food supplements.

By using the researchers' method, the team thinks that 5,000 tonnes of pure protein powder can be extracted from 60,000 tonnes of blood.

Rene Lametsch, Associate Professor and head researcher at Copenhagen university, said: “We are increasing production sustainability by taking advantage of pig blood as a protein source for human consumption.​

“It is likely that a growing number of people will satisfy their protein needs in the future through alternative food sources, for the sake of CO2 emissions and due to food shortages."​

Meanwhile, Dutch start-up Greencovery​ recently developed technology that helps food manufacturers recover valuable compounds from their side-streams. The resulting ‘high quality’ ingredients help the business offer an ‘attractive economical proposition’ that reduces CO₂ and water consumption.