Potato Starch To Plastic In A Day: What A Spanish Lab Breakthrough Could Mean For African Farmers

The humble potato, long a staple food and feed crop, has just taken on a surprising new role: raw material for making biodegradable plastic in a single day.

Researchers at the University of Barcelona have engineered a bacterium that can turn unprocessed potato starch into a high‑value bioplastic, polyhydroxybutyrate (PHB), in just 24 hours. The work, published in the journal Bioresource Technology, could open fresh markets for farmers and agri‑processors – especially where potatoes and other starchy crops are already piled high as low‑value by‑products.

Led by Professor Pere Picart from the university’s Faculty of Pharmacy and Food Sciences, with key contributions from microbiologist Mercedes Berlanga of the same faculty and the Biodiversity Research Institute (IRBio), the team has shown that a common, safe bacterium can be turned into a small bioplastic factory.

Why Turning Potato Waste Into Bioplastic Matters

Every year, hundreds of millions of tonnes of petrochemical plastics roll off production lines worldwide. Much of it ends up in soils, rivers, and oceans, or is incinerated – adding to greenhouse gas emissions and a mounting waste crisis.

PHB offers a different path. It is a biodegradable biopolymer produced from renewable resources. When used and disposed of correctly, it can partially close the carbon loop, breaking down instead of lingering for decades. Life‑cycle studies cited by the Barcelona team indicate that bio‑based plastics such as PHB often carry a smaller carbon footprint than many conventional plastics, particularly when they use waste‑derived raw materials.

For African agriculture, where tonnes of potato, cassava, and maize starch residues accumulate every season, the idea of turning such materials into higher‑value bioplastic fits cleanly with circular economy goals and climate targets under the AU Agenda 2063 and the UN Sustainable Development Goals.

The Bacterium Behind The Breakthrough

At the heart of the study is Bacillus subtilis, a gram‑positive bacterium already widely used in industrial biotechnology to make enzymes and chemicals. It is non‑pathogenic, grows quickly, and tolerates tough production conditions – all qualities industrial producers like.

FFA Explainer:

Polyhydroxybutyrate (PHB) is a type of polyhydroxyalkanoate (PHA), a family of biodegradable plastics made naturally by certain bacteria as energy storage granules. PHB can be processed into films, packaging, and moulded items, and it breaks down in the environment faster than most oil‑based plastics.

The authors of the study point out that commercial PHB production needs microbial hosts that are safe, easy to modify genetically, fast‑growing, and able to use a variety of carbon sources. Until now, B. subtilis had not been systematically developed as a PHB workhorse. Earlier studies reported PHB accumulations below 13% of the bacterium’s dry cell weight – too low for industrial comfort.

To change that, Picart’s group turned to CRISPR‑Cas9, the gene‑editing tool that allows scientists to cut and paste DNA with remarkable precision.

Rewiring Bacteria With CRISPR To Eat Starch And Make Plastic

Using CRISPR‑Cas9‑based genetic engineering, the team redesigned the metabolism of B. subtilis to push more carbon into PHB.

The key steps included:

• Genomic integration and constitutive expression of phaA: This gene is part of the PHB synthesis pathway. Locking it into the genome and keeping it switched on steers metabolism towards polymer production.
• Controlled expression of the phaRBC operon: These genes are involved in the formation and regulation of PHB granules inside the cell. Fine‑tuning their expression helps the bacterium accumulate more polymer efficiently.
• Adding the amyQ gene: This gene encodes an α‑amylase enzyme that can break down starch. With amyQ, the engineered B. subtilis can directly convert unprocessed potato starch into PHB in a single step.

In simple terms, the researchers equipped B. subtilis both with stronger PHB‑making machinery and with the ability to “chew” raw starch.

FFA Explainer:

CRISPR‑Cas9 is a genetic engineering tool adapted from bacterial immune systems. It acts like molecular scissors guided by a short RNA sequence, allowing scientists to cut DNA at precise locations and then insert, delete, or alter specific genes.

Using this combination of modifications, the team reports that in flask‑scale cultures they obtained 11.3 grams per litre of biomass and 5.8 grams per litre of PHB. The polymer accounted for 51.8% of the dry cell weight – a huge leap from earlier B. subtilis attempts and comparable in purity to commercial PHB.

Crucially, the process used unprocessed potato starch and delivered the polymer in a single 24‑hour step, which significantly simplifies industrial operation and could cut costs.

From Laboratory To Factory: What Needs To Happen Next

The study shows that B. subtilis can serve as a robust platform for PHB production from potato starch. It does not, on its own, guarantee that bioplastic bags or films made from African potatoes will hit supermarket shelves next year.

Scaling from flasks to fermenters brings challenges:

• Process optimisation: Industrial producers would still need to refine temperature, pH, aeration, and feeding strategies to maintain high PHB yields at large volumes.
• Feedstock logistics: Factories must secure reliable streams of starch‑rich by‑products (potato peelings, undersized tubers, processing waste) and manage their storage without spoilage.
• Downstream processing: Extracting and purifying PHB at scale determines final costs and environmental performance.
• Regulation and acceptance: Because the process uses genetically modified bacteria, regulators and consumers will scrutinise safety, confinement, and waste handling.

Yet, if these hurdles are managed, PHB from agricultural by‑products could become a central piece of the circular bioeconomy that many governments, including Zimbabwe’s under NDS1, say they want to build.

What This Could Mean For Potato Producers In Africa

The Barcelona breakthrough is rooted in European potatoes, but its implications stretch easily to African fields.

Across highland zones from Kenya’s Nakuru County to Rwanda’s Musanze and Zimbabwe’s Nyanga, potatoes are a key cash crop. Farmers and processors often face gluts, post‑harvest losses, and piles of low‑grade tubers that fetch poor prices.

FFA Explainer:

Agro‑industrial by‑products such as potato peelings, undersized tubers, or starch residues usually have limited uses, often going to low‑value animal feed or being discarded. Upgrading them into higher‑value products like bioplastics can improve farm incomes and reduce waste.

Imagine a starch processor outside Nyanga or Nyandarua that, instead of discarding waste starch, pipes it into a fermentation tank seeded with a licensed, engineered B. subtilis strain. Within a day, that waste stream becomes a bioplastic feedstock.

For rural economies, this kind of add‑on industry could:

• Create new jobs in fermentation operations, quality control, and maintenance.
• Offer farmers more stable offtake agreements for lower‑grade potatoes.
• Anchor local packaging production for agricultural products, reducing imports.

Zimbabwe’s potato producers in Nyanga and Chipinge, who already supply urban markets, could eventually link into such chains, especially if public‑private partnerships with universities and regional research bodies bring the technology closer.

Beyond Potatoes: Starch Crops And A Pan-African Opportunity

While the published study focuses strictly on potato starch, the authors note that their engineered B. subtilis system can handle multiple carbon sources. That raises a tantalising question for Africa: what about cassava, maize, or sorghum starch residues?

Countries such as Nigeria, Ghana, and Tanzania produce immense volumes of cassava every year. Zimbabwe and Zambia add mountains of maize bran and starch‑rich offcuts during milling. If future research – either in Barcelona or African labs – adapts similar microbial platforms for these feedstocks, the continent could start turning its starch surpluses into biodegradable plastics tailored for local markets.

The impact would sit at the intersection of several policy priorities:

• Food security: By focusing on by‑products, such systems need not compete with food uses of staple crops.
• Waste reduction: Agricultural waste becomes an input, supporting cleaner production targets.
• Climate action: Bio‑based plastics can cut reliance on imported oil‑based polymers and support national climate pledges.

Jobs And Skills For Youth And Women In The Bioeconomy

Bioplastic production is not only about tanks and genes. It is also about who gets the jobs.

Engineered B. subtilis fermentation plants need technicians, lab assistants, process operators, and logistics coordinators. These are roles that can fit well with young graduates from agricultural colleges and polytechnics, and with women who have often led the way in agrifood processing businesses.

For example, a women‑run potato processing cooperative in Nyanga that currently makes crisps and frozen chips could, in time, partner with a biotech start‑up to channel its starch waste into PHB production. Youth trained in microbiology and chemical engineering at the National University of Science and Technology or the University of Zimbabwe could become the process engineers and quality managers who keep those systems safe and efficient.

This is the sort of value‑addition pathway that African governments describe in their industrialisation strategies, but which rarely materialises at farm level. The Barcelona work provides a concrete, technically detailed model that can guide curriculum design, incubator programmes, and cross‑continental collaborations.

From Barcelona To The Barnyard: A Glimpse Of A Different Plastic Future

The paper by Maryia Shahayeva and colleagues, titled “One‑step polyhydroxybutyrate production from potato starch by engineered Bacillus subtilis,” does not pretend to solve the plastic crisis on its own. But it does demonstrate something important: with careful metabolic engineering, a familiar bacterium can convert an everyday agricultural by‑product into a high‑value, biodegradable material quickly and efficiently.

As the research team notes, technologies like this offer a chance to turn environmental problems into resources and support a more circular, decarbonised economy.

For African farmers and agri‑entrepreneurs, the next steps lie in partnership: linking universities, potato and cassava processors, and finance institutions to test whether such microbial platforms can thrive in Harare, Nairobi, or Kigali as well as they do in Barcelona.

Somewhere in a field on the Nyanga slopes, a farmer is pulling up a crate of small, misshapen potatoes the market will not pay for. In the future hinted at by this work, those rejected tubers might not be waste at all, but the raw material for the clear, biodegradable film wrapped around the vegetables in a supermarket a few hundred kilometres away.

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About The Author

Editor at Large

Farm & Future Africa (FFA) was born from the realization that Zimbabwe’s profound agricultural resilience and innovation needed a clear, authoritative voice to connect with the continent and the world.

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