Bacteria can now be used to make natural colors from simple sugar

Researchers at Rensselaer Polytechnic Institute have shown that four strains of E. coli bacteria working together can convert sugar into the natural red anthocyanin pigment found in strawberries, opening the door to economical natural colors for industrial applications. “The research marks the first biosynthesis method using four strains of bacteria to manufacture a compound in a single step”, said Mattheos Koffas, a professor of chemical and biological engineering at Rensselaer. “We feed the bacteria glucose and they do the rest”, he added.

Koffas’ lab has been investigating a production method of anthocyanins involving genetic engineering since 2005. In its current research, the molecular pathway was divided into modules among four different strains of bacteria and modified to assemble anthocyanin in stages. The modules produced intermediates that easily diffuse out of the bacterial cell. When combined in a single flask, the first bacteria ingest sugar and produce "intermediate" compounds, phenylpropanoic acids, which are then ingested by the second bacteria. This produces a second intermediate and this continues until the fourth strain produces anthocyanin.

In the next stage, researchers optimized each stage of the process. Each of the four strains was chosen based on its ability to produce its assigned intermediate. Some segments produced more than others, and the final output produced few milligrams per liter of anthocyanin. "I have no doubt that production of anthocyanins from a recombinant microbial host is the only viable method for making these compounds in an economically sustainable manner," said Koffas.