In a lab at the University of Barcelona, researchers have engineered a bacterium that does something remarkable: it transforms potato starch into biodegradable plastic in a single day. Using CRISPR-Cas9 genetic engineering, the team redesigned Bacillus subtilis—a safe, fast-growing microorganism already trusted by industry—to convert an abundant agricultural byproduct into polyhydroxybutyrate, or PHB, a high-value biopolymer that can decompose naturally instead of lingering in landfills and oceans for centuries.
This breakthrough matters because the world produces hundreds of millions of tons of petrochemical-based plastics annually, most of which ends up incinerated or accumulating in the environment. The process deepens our climate crisis and drives plastic pollution that now touches every ecosystem on Earth. Finding a renewable alternative that can be produced quickly and affordably is not just an environmental imperative—it's an economic one.
The research, led by Pere Picart, a professor at the UB's Faculty of Pharmacy and Food Sciences, with significant contributions from Mercedes Berlanga, was published in Bioresource Technology. The team tackled a fundamental problem: while Bacillus subtilis had theoretical potential to produce PHB, its actual capacity was limited, with previous studies showing accumulations below 13% of dry cell weight. These low yields made the bacterium impractical for industrial use.
The Barcelona team used sophisticated genetic engineering to fundamentally rewire the bacterium's metabolism. They genomically integrated the phaA gene and controlled expression of the phaRBC operon to enable efficient polymer accumulation from multiple carbon sources. Then came the crucial innovation: they incorporated the amyQ gene, which encodes an enzyme that breaks down starch directly. This single genetic addition allowed the redesigned bacterium to process unprocessed potato starch into PHB in one streamlined step, eliminating expensive preprocessing and reducing production costs dramatically.
The results speak for themselves. In flask-scale cultures, the engineered bacterium produced 11.3 grams per liter of biomass and 5.8 grams per liter of PHB—achieving a polymer purity of 51.8% of dry cell weight, matching commercial standards. What took multiple industrial steps now happens in 24 hours.
The environmental payoff is substantial. Unlike conventional petrochemical plastics, PHB is a renewable biopolymer made from agricultural waste. It degrades naturally, closing the carbon cycle and preventing the accumulation of persistent waste in terrestrial and marine ecosystems. Life-cycle studies show that bio-based bioplastics like PHB often carry a lower carbon footprint than their oil-derived counterparts, particularly when waste-derived feedstocks are used. Using potato starch—a byproduct of food processing—makes the process even more circular and cost-effective.
The research team frames their achievement as a genuine opportunity to transform an environmental liability into a valuable resource. Hundreds of millions of tons of potato starch are generated globally each year; most goes unused or becomes waste. Now that waste could become the raw material for biodegradable plastic, feeding a circular economy while reducing dependence on fossil fuels. For manufacturers, the speed and simplicity of the process—one step, 24 hours, using an affordable agricultural byproduct—makes it economically competitive. For the planet, it offers a tangible path toward reducing the toxic legacy of persistent plastic pollution.