StyGreen

Sustainable production of styrene from renewable sources

With our team we did not only develop our project design and performed many hours of labwork and modelling over the summer, we also paid attention to how our project fits into the society, safety, public engagement and education, entrepeneurship, visited many parties associated with our project and interviewed experts on their thoughts about our project and design. Besides all these amazing experiences, we also made collaborations with other iGEM teams and met them at several meetups! It has been an amazing summer. We want to thank all our sponsors, the donors on our crowdfunding page and all the people that have helped us to make our project successful!

Our challenge

The production of various chemicals is currently based on fossil fuels. Fossil fuels are however a finite resource which the world is using rapidly. Models indicate that oil resources will be depleted in the next couple decades [A]. Hence, there is an ever increasing attention for replacement with bio-renewable resources and more sustainable production processes. We believe that the transition away from fossil fuels towards a bio-based economy is one of the key challenges of the 21st century. Therefore, our iGEM team contributes to a future sustainable planet by investigating an alternative bio-based production route for the important chemical styrene.

Styrene

The monomer styrene is the basis of the industrial production of many plastic polymers, including Acrylonitrile Butadiene Styrene (ABS), Styrene Butadiene rubber or crosslinked polystyrene. Due to its apolar, aromatic structure, these materials have highly desired physical, chemical and electrical properties compared to other materials. Styrene furthermore is a versatile compound and is processed into numerous applications, which range from LEGO bricks to industrial rubbers, bike tires or isolation materials in electronic devices. Because of the thermoplastic properties of many polymers, these are recyclable. Styrene products are ubiquitous in our daily lives and irreplaceable for many industries, which is why the demand for styrene will inevitably outlast the availability of fossil fuels. The development of an alternative, sustainable production route is therefore of utmost importance.

StyGreen

With advances in synthetic biology, we can nowadays use microbes to produce biochemicals, which is a powerful technology to address the great challenges of our time. We therefore investigated the possibility to produce styrene with microbes. Styrene has a large structural similarity to phenylalanine, which is commonly present in living organisms, indicating that this makes a suitable precursor in a pathway towards styrene production by microbes. In fact, styrene production by microbes is highly feasible [B]. Therefore, we aim to make styrene in a sustainable manner by engineered microorganisms, a product we dubbed StyGreen.

Alternative to fossil fuels

To make StyGreen sustainable, it is of importance that the input into our process is a bio-renewable source of feedstock. Therefore, the final step is the need for a suitable input on which our StyGreen-producing microbes can grow. There are many possibilities that may serve as feedstocks for our cells, but we decided to seek for bio-based waste streams with low value specifically, which we can turn into the valuable StyGreen product. Microorganisms grow well on sugars, and a high number of waste streams contain large amounts of sugar in the form of glucose polymers, known as cellulose. Therefore, we investigated bio-renewable waste streams containing cellulose and subjected them to several criteria including technical, financial, economical and ecological factors.

A greener future

We aim to create a consolidated bioprocessing system by combining all the necessary steps to convert cellulose into styrene in one single microorganism: the yeast Saccharomyces cerevisiae. The StyGreen molecules that we produce can subsequently be used in all types of conventional industrial processes concerning non-single use plastics. In this manner, we ensure sustainable styrene availability and simultaneously a green environment for our future generations.

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