The secret ingredient in natural blue food dye: E. coli

A US researcher has found an unlikely ally in the quest to develop more natural food dyes: E. coli.

Originally synthesised from a bacterial strain, a deep blue dye known as indigoidine has offered a promising alternative to the synthetic dyes used to colour food, beverages, jeans, leather and paper.

However, the bacterium itself does not produce significant quantities of indigoidine, so researcher Dr Jixun Zhan from Utah State University (USU) created a method to mimic the organism’s biosynthetic machinery inside a heterologous host cell: E. coli. These mostly harmless bacteria can churn out significantly higher yields of the blue pigment and provide an efficient way to produce the dye without using synthetic compounds.

“In the original producing strain, there is only one copy of the biosynthetic gene that synthesises the pigment,” said Zhan. “But in E. coli. we can make multiple copies of the gene and induce its expression under a stronger promoter.”

Zhan has secured a patent for the process, which also includes the development of a new method to further process and purify the pigment before it’s ready for use — an important step when using the colourant in food and drinks. Business experts say the patent presents an exciting opportunity across several industries.

“The demand for natural dyes is growing rapidly,” said Christian Iverson, business development director for USU. “I’ve had a number of conversations with food and consumer product companies that are looking for natural dyes to replace some or all of the synthetic chemical-based dyes currently in use — in particular blue.”