Interview with Silvan Scheller, Assistant Professor for Biochemistry #32

Hello Human!

Today, it’s my honor to introduce you to Silvan Scheller, Professor in Biochemistry at Aalto University, Finland. Silvan is researching ways to turn the forest industry’s waste CO2 streams into fuels and chemicals with the help of microbes.

If you are not familiar with microbes and microbial engineering, I recommend reading the Survivaltech.club’s deep dive series on microbes!🦠

• Part 1: Introduction to the world of microbes
• Part 2: Microbes x Climate
• Part 3: Precision fermentation

As Bloom Biorenewables’ solution that we presented two weeks ago, Silvan’s research is providing our humankind solutions to move away from petroleum.

Before we dive into the world of microbe-made fuels and chemicals, I’ll share a few greetings from San Francisco!

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Pauliina’s greetings from SF

I’ve been in SF for 1.5 weeks now and loved it. People who I’ve met have had an incredible drive and been open and optimistic.

My highlight has been attending the Women in Climate Investing & Finance -event. I literally just scrolled through Eventbrite, found this event, and registered. I ended up meeting incredible women working in climate tech. Huge thanks to Meghan Pasricha and Marisa C. Sweeney for founding this amazing community.

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My learnings and observations:

• San Francisco is hilly. What looks like an easy and straight path on the map, might in reality mean that you end up pushing your bike steep uphill.
• People make intros. Fast. And you get replies fast. I’m starting to understand the power of this ecosystem and network.
• It is expensive to live here. Food, housing, transportation. Not to mention eating out.
• The number of homeless people is shocking. I’ve never seen this kind of insane contrast before. On the same street, you have millionaires with everything and masses of homeless people sleeping in tents.
• A lot of capital has entered the US climate tech market. Early-stage funding rounds are ballooning.

Kudos to Niko Laukkanen and the rest of the SILTA team for making this SF experience possible for me and seven other entrepreneurs from Finland!

Now, are ready to learn about making fuels and chemicals from waste CO2? Let’s go!

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🧠Wisdom from Silvan

What’s your background?

My original background is in chemistry. In fact, I didn’t know much about biology. Through some coincidences, I started working in a research group that studied a co-factor called F430. A co-factor is a molecule that helps an enzyme do its work and accelerate a biochemical reaction. For example, the cofactor F430 is required by the enzyme that makes methane in methanogens. Methanogens are microbes that can produce methane via a process called methanogenesis.

I was fascinated by how nature can produce methane via methanogenesis. The last step of this methanogenesis process is namely unknown by classical chemistry. Still, nature does it on a large scale! The goal of my Ph.D. thesis was to understand this last step better.  

After finishing my Ph.D., I went to do my postdoc at the California Institute of Technology in the US. Our research group studied microbes that can be found at the bottom of the ocean. Some of these microbes can naturally do something really cool: they can convert methane into CO2! I became fascinated by microbes and learned a lot about microscopy, microbiology, and genome sequencing.    

Via some detours, I arrived here at Aalto University, Finland, where I teach biochemistry and do research. Right now, my research focuses on converting CO2 to fuels by using microbes.

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Could you tell more about your current research?  

Recent research has found out that some microbes can convert ethane into CO2. Ethane is a molecule that has two carbon atoms bonded together by a single bond. These microbes that can convert ethane into CO2 have been found around deep-sea gas seeps, where ethane is present.

What I want to do is to reverse the reaction that these microbes do. This means designing a metabolic pathway that can convert CO2 into ethane. Later, I want to create a pathway from CO2 to propane. Propane is a hydrocarbon (= a molecule with carbon and hydrogen atoms) that has three carbon atoms.  

The idea is to feed CO2 from waste streams of the forest industry to the microbes. In this way, we could produce carbon-neutral, sustainable molecules. For example, propane is used to power our gas grills on balconies.

If hydrocarbons and alkanes are new to you, check out this great introductory video:

Which type of microbe have you started to work with?

We have started working with methanogens, which can already turn CO2 and hydrogen into methane. Methane is the simplest alkane with only one carbon atom and four hydrogen atoms. Currently, we can use these microbes to produce trace amounts of ethane: ca. 0.1% ethane, 99.9% methane.

We aim to engineer the methanogen to produce only ethane eventually and later propane. We strive to achieve this through enzyme engineering and adaptive laboratory evolution strategies.

The hydrogen will, of course, needs to be green. Green hydrogen is produced through electrolysis, splitting water into hydrogen and oxygen. The process needs to be powered by renewable electricity.

The below figure gives an overview of the ethane production process with microbes. Ethanogenesis refers to the process where microbes turn CO2 and green hydrogen into ethane.

If you are interested in learning about microbial engineering strategies, check out this open-access peer-reviewed article. Also, Survivaltech.club has written before about precision fermentation, the concept of engineering microbes to produce desirable products like ethane and propane.

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What are the key challenges you face in developing a microbe that can convert CO2 into alkanes?

The number one challenge is keeping the microbe happy.

When you engineer a microbe, you modify its naturally occurring metabolic pathways. A methanogen from the environment eats CO2 and produces energy (Adenosine triphosphate, ATP) for its functions, while it makes methane as a waste product.

Now, we aim to modify this metabolism so that the methanogen would produce ethane instead of methane. Still, the microbe should live and produce ATP for its cellular functions. This is the challenge.  

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What use cases do you have for alkanes like ethane, propane, and butane?

Hydrocarbons like ethane, propane, and butane can be used as fuels. Ethane, propane, and butane can be liquified at room temperature, unlike methane. This makes them easy to store and thus, increases their attractiveness as fuels.

Ethane can be used, for example, as a ship fuel. In fact, Wärtsilä, a Finnish company, built a marine vessel that can run on liquified ethane. It is worth mentioning that alternative fuels like ethane are still making a minority of ship fuels, as most ships run on heavy residual fuel oils.  

In the petrochemical industry, ethane is an important feedstock. Most ethane is used for ethylene production. Polyethylene (PE), the most common plastic today, is made from ethylene. Similarly, propane can be used as a feedstock to produce propylene. If you are interested in the different feedstocks in the petrochemical industry, check out this amazing article by Levi and Cullen, 2018 (Mapping Global Flows of Chemicals: From Fossil Fuel Feedstocks to Chemical Products).

Read more about Silvan’s research here!

If you are interested to learn more about the science behind this topic, check out these articles⬇️

• Fraçois, J. M., Lachaux, C., and Morin N. (2020). Synthetic Biology Applied to Carbon Conservative and Carbon Dioxide Recycling Pathways. Frontiers in Bioengineering and Biotechnology, 8. Link.
• Keasling, J. D. (2010). Manufacturing Molecules Through Metabolic Engineering. Science, 330 (6009), 1355-1358. Link.

• Müller, V. (2019). New Horizons in Acetogenic Conversion of One-Carbon Substrates and Biological Hydrogen Storage. Trends in Biotechnology, 37(12), 1344-1354. Link.

If you liked this article, please share it with your climate friends!💚🌍

Best, Pauliina