Who doesn’t love beautifully hued clothing? Well, how about Mother Nature? But can you blame her? Industrial dyes are absolute poison.
And that’s why researchers at the Korea Advanced Institute of Science and Technology (KAIST), through their Trends in Biotechnology paper “One-pot production of colored bacterial cellulose”, have offered the world so much hope for ecologically sustainable beauty. They’re using the bacteria Komagataeibacter xylinus to spin cellulose fibers for fabric, and the bacteria Escherichia coli to imbue those fibers with more hues than Joseph’s entire technicolor dream coat. Even more amazingly, they can do both in the same container.
But hold on – is the current industrial cloth-dyeing method really as bad as I’m saying?
Yes.
As senior author and biochemical engineer San Yup Lee explains, “The industry relies on petroleum-based synthetic fibers and chemicals for dyeing, which include carcinogens, heavy metals, and endocrine disruptors. These processes generate lots of greenhouse gas, degrade water quality, and contaminate the soil.”
Let’s add to that indictment. Creating dyes consumes massive amounts of water, and globally each year around 200,000 tons of dye escape industrial processes to pollute water systems. And these are some nasty, super-powered runaways, bred to resist light, temperature, soap, bleach, and even immersion, and because they’re imbued with anti-microbial agents, they decay very slowly.
Of course, because the very purpose of a dye is to change the color of other substances, dyes also change the color of the waters they pollute, degrading not just their beauty but their transparency. That loss of transparency leads to a reduction in photosynthesis for aquatic plants and thus a reduction in oxygen production, which further harms animals in lakes and rivers and reduces the irrigational value of that water. And if that list of crimes weren’t bad enough, many dyes are extremely toxic and even mutagenic.
Then there’s the secondary destruction of the entire industry that wouldn’t exist without dyes to make its products attractive: the over-production of fast fashion McClothes requires massive labor exploitation, carbon pollution because of shipping megatons of clothing across oceans, a culture of disposability that pukes garments by the ton into dumps we politely called “landfills,” or worse, shipping them across the ocean again as “donations” that destroy the domestic textile and clothing industries of developing countries.
So, good on KAIST for giving us a route to avoid all of that, but how does its method create a replacement for nylon and polyester, and dye it in the same vat pot?
During fermentation, a co-culture of the two types of bacteria uses derivatives of two natural pigments – violaceins and carotenoids – to produce a network of cellulose, the fiber that gives plant cell walls their stability, while also producing natural colorants for red, yellow, blue, orange, green, navy, and purple.
“At first,” says Lee, the process “completely failed. Either the cellulose production was much less than expected, or it never got colored.” His team soon discovered that Komagataeibacter xylinus, the bacteria that made the cellulose, and Escherichia coli, the bacteria that made the colors, were shafting each other.
So, how did the team “convince” the microbes to play nicely and make beautiful colors together? First, the scientists developed a delayed co-culture approach for the blue-family (green-to-purple color range) violaceins by adding the color-producing bacteria only after the cellulose-producing bacteria started growing. For the red-family (red-to-yellow) carotenoids, the researchers harvested and purified the cellulose before soaking it in the pigment-producing cultures. And voilá: all the colors of the rainbow were possible.
Of course, gorgeous colors in a laboratory are functionally worthless in the real world if a single dunk in the washing machine turns vibrant rainbows into a single shade of grey. So, to test the durability of the dye-job, the team attacked the colored fibers with a textile assault that could reduce any tie-dye to terrified tears: heating them, bleaching them, and even drowning them in alkali and acid. While some colors ran, others held their ground, proving the fibers they were made of. In washing tests, the violacein colors actually fared better than those obtained from synthetic dye.
So, how soon will we be buying bacterially produced-and-dyed clothing?
“Our work is not going to change the entire textile industry right now,” says Lee, estimating that KAIST’s method won’t be delivering fabrics to consumers for at least five years, given the time required to boost production capacity to compete with cheap petro-products.
“But at least we have proposed an environmentally friendly direction toward sustainable textile dyeing, while producing cellulose at the same time,” he says, refreshingly enthusiastic about the humanitarian mission of science. “It’s our duty as humans to make the world a better place and allow our children to live happier lives. Let’s be kind to the environment and do something good for future generations.”
Source: Cell Press via EurekAlert
