About 20 percent of the world's industrial water pollution comes from textile dyeing. And the denim industry is the worst offender: Most mass-market denim brands rely on petroleum-based dyes and chemicals like formaldehyde and hydrogen cyanide. In 2019, that reality inspired Tammy Hsu and Michelle Zhu to start Huue, which they spun out of Hsu's grad school work at the University of California at Berkeley, where she developed dyes made from microbial secretions. Huue is working on the launch of its first dye, a natural-but-synthetic indigo. The company's eight scientists are also developing sustainable dyes and colorants to disrupt other parts of the fashion industry. --As told to Hannah Wallace

ZHU: My parents were entrepreneurs in the apparel industry. Their brand focused on urban streetwear in the late '90s and early 2000s, which was why denim was such a large focus. As a child, I would visit garment manufacturing facilities on summer trips to China and witness the pollution firsthand: particles in the air that workers had to guard against with facemasks, and foul-looking waterways around the factories. It made a lasting impression on me.

HSU: I came at it from studying science and biology. The lab I was in was very entrepreneurial -- we were all thinking about how we could apply these solutions to real-world problems. I'm interested in fashion, clothes, and textiles. The more I read about it, the more I realized that this is a huge problem in the industry.

ZHU: Until the turn of the 20th century, indigo was made from plants. Natural indigo is not very cost effective or scalable, and its performance and color consistency doesn't fit industrial needs. Today, it is generally created via petrochemicals. Fossil fuels are used at the source of creation, but the industry also relies on toxic chemicals such as formaldehyde and benzene -- which not only pollute the planet but are carcinogenic as well. That's the main challenge we're tackling.

HSU: We look at how the indigo plant makes the indigo dye molecule. Then we take that genetic information and instruct our microbes to make indigo the same way. We're growing these microbes, and they're programmed to secrete the indigo.

ZHU: Microbes are truly amazing -- they multiply rapidly. We call them nature's most powerful manufacturers.

HSU: Six years ago, my professor at Berkeley had a grant, and a story was written about our project. When people learned we were working on sustainable indigo, brands started inquiring.

ZHU: We'd just hired our team of scientists and everyone was so excited to get to work last year. And then it was all shut down. Our milestones are lab-based, so not being able to go into the facility for three months created all sorts of uncertainty. Then there was the issue of when we could run productions and supply products. We were fortunate to win a female founders competition hosted by Microsoft's M12 fund, Mayfield, and Melinda Gates's Pivotal Ventures. That gave us an extra million dollars, which was a big help in the midst of Covid. Finally in July 2021, we brought the whole (vaccinated) team back into the lab full time.

HSU: We've made a lot of progress to scale up our production with a couple of facilities around the U.S. and to make our microbes more efficient. In August, we were producing 80 times more dye than at the end of last year. Our partners want huge amounts of dye.

ZHU: The fashion industry is aware of its challenges -- its troubled supply chain and the toxic nature of the dyeing process. It hasn't been difficult to get people really excited about the technology and potential.