Soon, we’ll be able to stop and smell the roses (without the flowers). Biotechnologists have developed ways of synthesising natural products—such as the chemicals that give flowers their unique and recognisable scents—under controlled and scalable industrial conditions. The process, known as metabolic engineering, is said to be a more sustainable way of attaining natural compounds for food, cosmetics and pharmaceuticals.
“Many natural products are obtained through natural extraction, which would require significant natural resources such as water and land,” explained Xixian Chen, a Junior Principal Investigator from A*STAR’s Singapore Institute of Food and Biotechnology Innovation (SIFBI).
For example, up to 3,500 square kilometres (or about five times the land area of Singapore) of agricultural land space is required to extract 10 tonnes of cis-α-irone—a sweet, woody-scented chemical from iris plants that’s highly prized by the perfume industry.
Traditional methods for the production of cis-α-irone have several shortcomings—the process is slow, still relies on iris plants as a starting material and involves complex enzymatic reactions, many of which have yet to be characterised.
“Until today, experts have no idea exactly how nature makes cis-α-irone; it’s still quite challenging to perform gene discovery for such compounds that are naturally present at very low concentrations,” said Chen.
Chen and colleagues hypothesised that a method heavily used in organic chemistry—retrosynthesis—could help unlock novel ways of producing cis-α-irone. In collaboration with Isabelle André’s team from the Toulouse Biotechnology Institute in France, the researchers built an artificial pathway with a promiscuous methyltransferase (pMT) for the synthesis of cis-α-irone, and focused on improving the activity and specificity of pMT.
First, they analysed the crystallographic structure of pMT to identify specific amino acid residues that could be critical in improving the enzyme’s efficiency.
Next, they synthesised different variations of pMT with mutations at these key residues and performed computational simulations to gain insights into the interactions between mutated residues and cis-α-irone. Finally, the optimised pMT enzyme was used to convert glucose into cis-α-irone in specialised bacterial cells using precision fermentation.
By enhancing the pMT enzyme's performance, the researchers achieved a 10,000-fold increase in its activity and a 1000-fold increase in its specificity, thereby producing significantly higher cis-α-irone yields.
“This has led us to rethink many natural pathways that have room to be improved upon in terms of carbon yield and performance,” said Chen, adding that their approach could mark a new era of sustainable metabolic engineering across many industries.
The team is currently collaborating with A*STAR’s in-house robotics platform, SPARROW (SIFBI PARallel RObotic Workstation), and the Centre for Frontier AI Research (CFAR) to further fine-tune these and other enzymatic pathways.
The A*STAR-affiliated researchers contributing to this research are from the Singapore Institute of Food and Biotechnology Innovation (SIFBI).
