Microbial fermentation could offer cost effective production method for anthocyanins, say researchers

Photo by Ken Hammond

Microbes can convert sugar into the red anthocyanin pigments found in fruits via a fermentation process that – when perfected – could prove to be much more efficient than extracting commercial quantities of these pigments from plants, claim researchers. 

Scientists at Rensselaer Polytechnic Institute in New York divided the complex, multi-stage, molecular pathway for producing anthocyanins among four different strains of E. coli bacteria, which were genetically engineered to assemble anthocyanin in stages.

When combined in a single flask, the first bacteria ingest sugar and produce ‘intermediate’ compounds (phenylpropanoic acids), which are ingested by the second bacteria, which produces a second intermediate, and so forth until the fourth strain produces anthocyanin.

The research – published in the journal mBio - “marks the first biosynthesis method using four strains of bacteria to manufacture a compound in a single step,” said Mattheos Koffas, professor of chemical and biological engineering at Rensselaer, and member of the Center for Biotechnology and Interdisciplinary Studies.  

“For the first time, we are able to completely synthesize anthocyanins in a biological system. We feed the bacteria glucose and they do the rest. This demonstrates that an inexpensive technology can produce these valuable compounds.”

‘The anthocyanins we are making using recombinant microorganisms have the exact same properties as the compounds you extract from plants’

The next step is to optimize each stage of the process such that production approaches hundreds of milligrams per liter, added Koffas.

“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.”

Asked about the commercialization strategy, he told FoodNavigator-USA: “We have filed for a patent and this has been the main focus as of now. Our thinking is we would find a commercial partner interested in licensing the patent and moving to scale up the process and manufacture the compounds.”

As for the properties of the anthocyanins in terms of heat, light and pH stability, he said: “The anthocyanins we are making using recombinant microorganisms have the exact same properties as the compounds you extract from plants.

"They have higher stability at low pHs, they are not light sensitive and the color changes when the pH changes. They are stable at room temperature for at least 30 hours (we haven't tested stability for longer periods of time). At 4 C they are stable for days.”

Asked about the regulatory, labeling, and consumer acceptance issues this raises (some consumer groups have already come out strongly against ingredients produced via synthetic biology, while the Non GMO Project will not certify products made using genetically engineered microorganisms), Koffas noted that several colors, flavors, sweeteners and stabilizers are already produced via microbial fermentation because it is more efficient and scalable than extracting the ingredients in question from plants.  

‘A new paradigm in metabolic engineering’

Writing in mBio, Koffas et al explained the significance of the work: “This study… provides a new paradigm in metabolic engineering for the reconstitution of extensive metabolic pathways in nonnative hosts.”

The development of polycultures (combinations of 3+ strains in a single co-culture), “is an important next step toward the goal of developing synthetic consortia that can rival the complexity of systems found in nature,” he added.

“The consortium-based approach presented in this proof-of-principle study is not limited to flavonoids but in principle could be applied to a variety of other high-value natural and synthetic products. In summary, coculture and polyculture techniques have demonstrated their potential to rapidly expand what is deemed to be possible with metabolic engineering.”

Source: mBio: doi: 10.1128/mBio.00621-176 June 2017 mBio vol. 8 no. 3e00621-17

Complete Biosynthesis of Anthocyanins Using E. coli Polycultures

Authors: J. Andrew Jones, Victoria R. Vernacchio, Shannon M. Collins, Abhijit N. Shirke, Yu Xiua, Jacob A. Englaender, Brady F. Cress, Catherine C. McCutcheon, Robert J. Linhardt, Richard A. Gross, and Mattheos A. G. Koffas

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