SDSU researcher developing natural alternative to synthetic dyes

At South Dakota State University, researcher Ananda Nanjundaswamy already is working on the solution — scaling up production of natural pigments derived from microbes — a safe, nutritional alternative to synthetic dyes like Red No. 3, which has been linked to cancer in male lab rats and is banned already in food products in Europe, Australia and New Zealand.

Synthetic dyes are prevalent in the U.S. food supply and are found in candies, ice cream, drinks and even medications. These synthetic dyes do not add any flavor or nutritional value and are used solely to give foods and other products the colors consumers are long accustomed to.

But a growing body of research links synthetic dyes to significant health problems. In addition to Red No. 3, other synthetic dyes, like Red No. 40, have been linked to hyperactivity and neurobehavioral problems in children.

Food manufacturers will have until January 2027 to completely phase out synthetic dyes from their foods. Until then, companies may be looking toward innovative biotechnologies — like the one being developed by the lab in SDSU’s department of biology and microbiology — as a replacement.

Natural pigments
Nanjundaswamy is SDSU’s Richard and Janice Vetter Endowed Associate Professor of Biotechnology and Bioprocessing. His research is focused on bioprocessing and fermentation for product development. In recent years, he has focused his efforts on using microbes — microscopic organisms like bacteria, fungi and algae — for the source material of compounds that may be used in human food and animal feed.

South Dakota State University’s Ananda Nanjundaswamy is developing a natural and safe alternative to synthetic food dyes.

“In the last few years, my research focus is on natural food color production,” Nanjundaswamy said. “Natural food colors are the next alternative to synthetic food dye.”

As he explains, microbes live naturally on plant surfaces and in the soil and are known to be nature’s producers of natural colors. Carotenoids are a class of molecules that are responsible for the naturally occurring pigments in plants and animals.

“Carotenoids are a group of molecules which fall into the category of simple lipids,” he said. “They are produced by fungi, yeast and sometimes bacteria.”

There are more than 1,100 identified carotenoids, and they can be categorized into two classes: xanthophylls and carotenes. Different carotenoids provide different colors. For example, salmon have a distinct pink or reddish color. This is thanks to the carotenoid astaxanthin, which salmon acquire after consuming algae or krill. Flamingos have a similar response to consuming microbes with astaxanthin.

But it’s not just coloring that carotenoids provide. The molecules also have antioxidant properties, meaning they prevent some types of cellular damage and offer pro-vitamin A activity, adding nutritional value to foods.

“There are two ways these molecules can be used,” Nanjundaswamy said. “One is natural colors. The second is as a nutritional molecule.”

Using ag byproducts
The Upper Midwest is the U.S.’s largest sugar beet-producing region, and molasses is a byproduct of sugar beets. For most, molasses is a little-used, bulk commodity that can be purchased rather cheaply. In Nanjundaswamy’s lab, researchers are using molasses as the carbon source to grow different microorganisms that are known producers of carotenoids.

In benchtop bioreactors, Nanjundaswamy and his team are optimizing the conditions for fungus and yeast to be grown in molasses. As the fungus and yeast grow, the research team is extracting the colorful carotenoids and other useful “goodies” produced by the microbes.

“Carotenoid-producing yeast are also very good producers of lipids,” he said. “Lipids are very useful for animals as well as humans.”

The lab is focused mainly on red and yellow colors, which means they are focused on astaxanthin, beta-carotene and other molecules under the carotenoid umbrella. The extracted carotenoids are the end product of Nanjundaswamy’s research, and they can be mixed into different foods to give them rich colors.

In ancient times, natural ingredients were used to add colors to foods. In the middle of the 19th century, scientist William Henry Perkin was credited with discovering the first synthetic dye. By the turn of the century, it was extremely common for foods, drugs and cosmetics to have synthetic dyes in them.

One of the major reasons synthetic dyes became so popular is because they are cheap to produce — far cheaper than natural food colors. This represents one of the major challenges Nanjundaswamy faces in developing commercially viable natural food dyes. Extracting natural pigments is an expensive, inefficient process. But using molasses as a carbon source is one of the ways the researcher is circumventing the cost challenges.

“We use these inexpensive agricultural products like molasses for our work,” he said. “The inexpensive coproduct you are generating from one industry can serve as a feedstock for another industry. That’s what is known as the circular economy, and that’s what’s happening here.”

Another byproduct Nanjundaswamy is exploring is high fructose corn syrup. In the Midwest, high fructose corn syrup is produced in very high quantities and could be used as a nutritional base to grow carotenoid-rich microbes.

Scaling up
In Nanjundaswamy’s lab, scientists have proven they can grow and extract naturally occurring pigments successfully. But for this research to have an impact at a societal level, Nanjundaswamy is working to scale up his research for commercial use.

In 2023, Dakota BioWorx opened at the Research Park at SDSU. This state-of-the-art bioprocessing facility is precisely the space Nanjundaswamy needed to move his work from the lab to the marketplace. Dakota BioWorx has a variety of bioreactors with capacity ranging from 30 to 3,000 liters and downstream processing equipment that will allow him to produce large quantities of carotenoid-rich microbes.

These bioreactors also will allow him to gain a better understanding of the processes taking place inside production containers of different sizes.

“From an engineering point of view, what happens in a 7-liter flask will be totally different than what happens in a 3,000-liter bioreactor,” Nanjundaswamy said.

Last year, the researchers produced a 70-liter batch at Dakota BioWorx, which provided them vital information on the processes and challenges in scaling up their work.

Currently, Nanjundaswamy and the research team are looking to acquire additional funding that will allow them to conduct scale-up feasibility studies.

“These studies will provide cost-benefit ratios and techno-economic analyses,” he added.

Nanjundaswamy is studying a number of processes and conditions for his product development. The team is trying to better understand product stability and suitable storage conditions, as well as downstream processing. The team has filed U.S. provisional patents on the processes and the end products they have developed.

“These are all very important in product development. These products have a lot of commercial potential.”

Applications beyond food
Nanjundaswamy’s research team is not solely focused on natural food coloring production. He started this work with the intention of using it in animal feed and believes the same processes and products could be used to make naturally sourced color additives for animal feeds.

Currently, the ban on synthetic dyes applies only to the food industry, but some believe the U.S. Department of Agriculture could ban synthetic dyes in animal feed in the future.

Aside from human food and animal feed, Nanjundaswamy’s products potentially could be used in personal care products.

Synthetic dyes make up roughly 70 percent of the color additive market. The forthcoming ban and potential bans in other industries will open up the market for new products like the ones Nanjundaswamy aims to produce. It’s an especially exciting time for his lab as he believes he has a leg up on potential competitors in the market.

“I think we are way ahead of others,” he said. “My lab has already optimized these material processes. Now, it’s just a matter of scaling up.”

State of innovation
The work being done at SDSU is an example of the innovation occurring in South Dakota’s biotech industry.

“It’s exciting, impactful research that’s exactly what was envisioned with the Dakota BioWorx facility,” said Joni Ekstrum, executive director of South Dakota Biotech. “It’s the right work at the right time, and the potential here appears to be significant.”