Ezhil Subbian built String Bio to turn a greenhouse gas into protein

Methane is one of the more uncomfortable facts of the climate problem. Over a twenty-year horizon it traps far more heat than carbon dioxide, and it pours out of paddy fields, landfills, livestock and energy infrastructure in enormous volumes. Most of the world treats it as something to capture, flare or apologise for. Dr Ezhil Subbian looked at the same gas and saw a raw material that nobody was using.

String Bio, the Bengaluru company she co-founded in 2013, feeds methane to microbes inside large fermentation tanks and harvests what those microbes produce. The output is protein for animal and fish feed, and nutrition inputs that go back onto farms. It is an unusually ambitious piece of industrial biotechnology to attempt from India, and in July 2022 it drew a 20 million dollar Series B, with an Australian energy major among the investors precisely because it wanted the technology for its own methane.

A scientist trained across two continents

Subbian is a scientist first, and her credentials are unusually deep for an Indian consumer-facing startup ecosystem that often rewards speed over rigour. She studied industrial biotechnology at Anna University in Chennai, taking a B.Tech in a discipline that was still relatively novel in India at the time. That early exposure to the industrial side of biology, the business of making useful things with living systems rather than simply studying them, set the direction for everything that followed.

She then moved to the United States for doctoral research in biochemistry, biophysics and molecular biology, with work associated with Oregon Health and Science University and Rutgers University in New Jersey. Different profiles describe the arrangement of those doctoral years slightly differently, so the fair summary is simply that she emerged as a serious research scientist in protein science and molecular biology, with the training to design biological systems rather than merely observe them.

Fifteen years scaling biology in American industry

The part of her career that matters most for String Bio is what she did after the laboratory. Subbian spent more than 15 years in industrial biotechnology in the United States, working on the engineering and scale-up of biobased products. That included time at Codexis, a company built on engineered enzymes, and at Gevo, a renewable chemicals and fuels business founded with the involvement of a Nobel laureate.

Scale-up is the unglamorous discipline that decides whether a biotechnology company lives or dies. A microbe that behaves beautifully in a flask often fails at a thousand litres, and again at a hundred thousand. Yields drop, contamination creeps in, the economics stop working. Subbian spent a decade and a half inside exactly that problem, learning where biological processes break when you make them big. Very few founders anywhere start a fermentation company with that specific scar tissue. It is the reason String Bio was built around manufacturability from the beginning rather than as an afterthought.

Why she came back to India to start String Bio

Around 2012 and 2013 Subbian and her co-founder, Vinod Kumar, began building String Bio, and she made the decision to base it in India rather than in the American ecosystem where her career had been made. The logic was sound even though it was harder. India has enormous quantities of distributed methane, from agriculture and waste, and an equally enormous demand for protein and for affordable inputs that improve farm productivity. Both ends of the problem sat in the same country.

There was also a gap she was well placed to fill. India produced a great deal of excellent biological research and comparatively few companies that turned it into industrial products at scale. Choosing India meant accepting a shortage of deeptech capital, a thinner base of specialised fermentation talent and investors who mostly wanted software returns on software timelines. It also meant that if the technology worked, it would be built where the raw material and the need actually were.

How the technology works

String Bio's core asset is a proprietary process it calls the String Integrated Methane Platform. In plain terms, the company cultivates microorganisms that consume methane and grow on it. Methane is fed into large fermentation tanks under carefully controlled conditions, the microbes multiply, and the resulting biomass is processed into a protein-rich material and other useful fractions. The facility outside Bengaluru runs the process in a highly automated way, which matters because consistency is everything in fermentation.

The elegance of the idea is that it inverts the usual relationship between food production and land. Conventional protein for animal feed comes from soy or from fishmeal, which means farmland, fresh water, fertiliser or pressure on wild fish stocks. Methane fermentation needs none of that. It needs gas, a tank and a well-behaved microbe. The protein is effectively decoupled from arable land, which is the strategic argument for the whole category.

The products and where they are used

String Bio has taken its platform into two commercial directions. The first is protein for animal feed and aquaculture, a market that grows with every increase in fish and poultry consumption and is structurally short of sustainable inputs. Aquafeed in particular is a natural early market, because fish farming has an obvious and expensive dependence on fishmeal.

The second direction is agricultural inputs. The company sells biostimulants, including a microbial product marketed as CleanRise and a peptide-based product called Impakt, designed to improve crop performance and support more sustainable food production. CleanRise has been positioned for rice cultivation, which is a satisfying detail, because flooded paddy fields are themselves one of the significant agricultural sources of methane emissions. A product born of methane going back into the crop system that emits it closes a loop rather neatly, and it puts String Bio in front of farmers whose own productivity is the measure of whether the science was worth doing.

Funding and the Woodside Energy vote of confidence

Deeptech of this kind is patient work, and String Bio spent years on research, pilot plants and process engineering before it looked like a scaled business. Early support came from investors willing to accept long timelines, including Ankur Capital, an impact-oriented fund that has backed several Indian science-led companies, along with other early-stage backers.

The defining round was announced in July 2022, a Series B of about 20 million dollars with several investors participating. The most interesting name on the list was Woodside Energy, the Australian energy company. Woodside was not a passive financial investor looking for exposure to Indian biotech. Its leadership spoke publicly about the possibility of using String Bio's technology to recycle methane at Woodside's own facilities. When a large industrial emitter invests in a startup because it may want to deploy the technology on its own sites, that is a stronger signal of technical credibility than any valuation headline. It suggests the process works at a scale that matters to people who operate real plants.

The difficulty of building deeptech from India

It is worth being straight about how hard this path is. A fermentation company cannot iterate the way a consumer app does. Every improvement runs at the speed of biology and of capital equipment, experiments take weeks, and a new plant takes years and a great deal of money. Investors who are comfortable with a two-year path to revenue are rarely comfortable with a ten-year one, and India has fewer of the latter than the United States or Europe.

There is also the commercial reality that String Bio is selling into price-sensitive markets. Feed and farm inputs are bought on economics, not on sentiment. A sustainable protein has to compete with soy and fishmeal on cost and performance, or it stays a pilot forever. The company's progress should be read in that light, as a long technical project working toward genuine cost competitiveness rather than a finished commercial victory. That is the honest framing, and it takes nothing away from what has been built.

Ezhil Subbian's net worth and ownership

There is no verified public net-worth figure for Ezhil Subbian, and readers should treat any number they find online as invention. String Bio is a private, venture-backed company. It has not disclosed the valuation attached to its Series B, and the founders' individual shareholdings are not on the public record. In a capital-intensive deeptech business that has raised institutional rounds, founder equity is diluted meaningfully along the way, and whatever stake she holds is paper wealth in a company still building toward full commercial scale. The verifiable facts are the science, the platform and the roughly 20 million dollars raised in the Series B. Everything beyond that is private.

What Ezhil Subbian's story teaches Indian founders

The first lesson is that deep expertise is a legitimate founding advantage, and it compounds. Subbian did not spot a market gap and hire scientists to chase it. She spent 15 years learning precisely how biological processes fail at industrial scale, then built a company around that knowledge. In sectors where the hard part is genuinely hard, the founder who has already made the expensive mistakes elsewhere starts years ahead of a smart generalist.

The second lesson concerns where a founder chooses to build. Coming back to India cost her access to the deeptech capital and specialist talent pools she could have drawn on in the United States. What she gained was proximity to the actual problem, abundant distributed methane and a country that needs affordable protein and better farm inputs. Building where the problem lives is often slower and almost always more defensible. Indian founders looking at climate, agriculture and industrial biology should take the point seriously, because these are categories where the country's own conditions are the competitive advantage.

Frequently asked questions about Ezhil Subbian and String Bio

Who is Ezhil Subbian?

Dr Ezhil Subbian is the co-founder and CEO of String Bio, a Bengaluru industrial biotechnology company that converts methane into protein and crop nutrition products. She holds a B.Tech in industrial biotechnology from Anna University and did doctoral research in biochemistry, biophysics and molecular biology in the United States, then spent over 15 years scaling biobased products at American companies including Codexis and Gevo.

What does String Bio do?

String Bio uses a proprietary fermentation process called the String Integrated Methane Platform to feed methane to microbes and convert it into useful products. These include protein for animal feed and aquafeed, and crop biostimulants sold as CleanRise and Impakt. The approach turns a potent greenhouse gas into a food-system raw material.

How much funding has String Bio raised?

String Bio raised a 20 million dollar Series B announced in July 2022, with several investors participating, including Ankur Capital and the Australian energy company Woodside Energy, whose leadership noted interest in using the technology to recycle methane at Woodside facilities.

Why is turning methane into protein important?

Methane traps far more heat than carbon dioxide over a short horizon and is emitted in large volumes by agriculture, landfills and energy operations. Using it as a feedstock tackles two problems at once, keeping some methane out of the atmosphere and producing protein without the farmland, fresh water or wild fish stocks that soy and fishmeal require.

Where is String Bio located?

String Bio is headquartered in Bengaluru, with a highly automated manufacturing and fermentation facility located outside the city. The company was founded in 2013 by Ezhil Subbian and Vinod Kumar.

What is Ezhil Subbian's net worth?

There is no verified public net-worth figure for Ezhil Subbian. String Bio is a private, venture-backed company, its valuation has not been publicly disclosed, and her individual shareholding is not on the record. Any specific figure circulating online is unverified.