Material World: Bacteria-Based Bio-Leather is Booming

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The Material Innovation Initiative (MII) has published its third Start of the Industry Report for the next-gen materials sector.

Per the report, next-gen material companies raised at least $456.75 million from 28 publicly disclosed deals in 2022. Last year represented a more challenging investment atmosphere for the industry than 2021, but looking at the 10-year period from 2013 to 2022, the capital invested and the number of deals continued their upward momentum. Sixty-nine new companies have been formed and 214 deals have been made since 2013.

While a lot of those companies are tackling the leather industry with plant-based solutions like mycelium, alternative methods are also sprouting up.

“Alternative proteins and precision fermentation will continue to expand to improve control of ingredient supply chains for various industries, from food and agriculture to materials and medicine,” David Kaplan, professor of biomedical engineering at Tufts University, predicted in MII’s report.

And he was right.

Researchers at Columbia University and the Fashion Institute of Technology (FIT) are developing a compostable, flame-retardant bio-leather based on microbial nanocellulose. Dr. Theanne Schiros, associate professor at FIT and research scientist at Columbia University in the Materials Research and Science Center (MRSEC), is the innovator behind the microbial bio-textile, in scientific partnership with professor Helen Lu and Romare Antrobus of Columbia University Biomedical Engineering.

“I certainly never thought I would have a career, or be working in, fashion, so to speak; I’m a scientist first and foremost,” Schiros said on an episode of CBS’s “Mission Unstoppable,” a show that highlights female innovators. “But in truth, STEM has everything to do with fashion.”

Schiros demonstrated what she called a potential “fiber factory of the future,” sweet tea-feeding bacteria spinning new materials for this leather alternative. The bio-fabrication process begins with feeding the bacteria a carbon source—in this example, the sugar in the tea—and a nitrogen source, the tea itself. As the bacteria eat, it creates cellulose, which sits atop the liquid as a hydrated biofilm called pellicle. Drawing inspiration from pre-industrial and indigenous science, the pellicle goes through a plant-based lecithin emulsion process before it becomes the leather-like biomaterial.

On Netflix’s “The Future Of,” Schiros again showed this bio-leather made from microbial nanocellulose, this time fabricated into a pair of entirely nanocellulose-based sneakers apart from a biodegradable cork bottom.

“In principle, you could cut it up and put it in your compost bin,” Schiros said on the show.

These microbial bio-leather sneakers, made in collaboration with Public School, New York, are on exhibition at the Montreal Museum of Fine Arts.

But there’s another element to this biomaterial: it’s inherently flame-retardant.

“The cool thing about nature is that it can take [two things] and give them the exact same material, but totally different properties by how it’s assembled. The same is true for cellulose. Nanocellulose is identical in chemical structure to plant cellulose, but the way it’s arranged gives it totally different properties,” Schiros told Sourcing Journal. “So even the untreated nanocellulose has a high degree of flame retardance and that’s because of what we call hierarchical assembly.”

In layman’s terms, the hierarchy is how it’s built, from the molecule up, and differences in that can change emergent properties dramatically. What’s particular about this material is that it comprises nanofibrils, Schiros explained, interlinked into a dense mesh. That nanofiber film grows at the liquid media-air interface until it covers the surface, and then another one grows, and so forth. This is where flame retardance comes into play: the densely packed mesh layers limit the oxygen’s (no pun intended) breathing room to ignite the fuel (aka, the cellulose) properly.

“The 2-D meshes are organized in this multilayer structure which mimics that of a multilayer flame-retardant structure,” Schiros said. “So even the untreated nanocellulose has a degree of flame retardance because of the way this bio-material self assembles from this bacteria. It’s pretty cool.”

Then there’s the paleo-inspired tanning treatment element, which adds phosphate groups that redirect the chemical pathway of combustion. So when you add a flame, the bio-leather doesn’t ignite.

“I think what the big lesson learned was that combining microbial bio-fabrication, bio-based green processing and waste-to-resource strategies for both dyeing and for sourcing raw materials produces a regenerative, high-performance textile with a dramatically reduced environmental impact,” Schiros said. “This is an order of magnitude lower environmental footprint; it’s got a 97 percent lower carbon footprint [than] vegan synthetic leather.”