If you’ve heard that a glass of red wine a day is good for your health, you may wonder what exactly makes red wine beneficial. It turns out that a chemical compound in grape skin, called resveratrol, confers onto red wine a variety of biological properties ranging from anti-aging to cardiovascular protection.
As would be expected, resveratrol quickly garnered attention from the nutraceutical and beauty industries for its use as a dietary supplement. But attempts to commercially manufacture resveratrol using genetically engineered Escherichia coli and Saccharomyces cerevisiae have met with little success to date.
“Engineering microbial cell factories for the sustainable production of important chemicals is often limited by the lack of high-throughput detection methods,” said Ee Lui Ang, now a Team Leader in the Discovery and Transformation division at A*STAR’s Singapore Institute of Food and Biotechnology Innovation (SIFBI). “This means that researchers are unable to screen through vast libraries of genetic variants generated by mutagenic methods to find the variants with higher production titers.”
Looking to find a way to produce valuable chemicals sustainably, Ang and colleagues sought to develop a biosensor that enables the high-throughput screening of resveratrol production in microbial cells.
Transcription factors are nature’s biosensors, triggering a cellular response when bound to specific compounds. However, before this study, there were no transcription factors known to be responsive to resveratrol. Therefore, the researchers searched for novel transcription factors by mining the genome of a bacterium called Novosphingobium aromaticivorans, which is known to break down resveratrol naturally.
“We hypothesized that N. aromaticivorans may have a sensing mechanism to detect resveratrol compounds,” said Ang. Genome analysis revealed a putative transcription factor gene upstream of a known resveratrol degradation enzyme, which the research team incorporated into their biosensor.
Characterization studies of the candidate transcription factor confirmed its sensitivity to resveratrol. The biosensor could accurately distinguish resveratrol from its precursors, p-coumaric acid and trans-cinnamic acid, and detect other biologically active stilbenes and cannabinoids.
When coupled to resveratrol biosynthesis enzymes, the biosensor sensed changes in resveratrol production in cells, demonstrating a 667-fold enrichment in one round of fluorescence-activated cell sorting. This suggests that the biosensor can potentially be used to identify genetic variants with high production titers in directed evolution experiments.
The researchers are looking to develop similar biosensors for other high-value compounds by mining the genome of microbes for new transcriptional regulators.
“At this point, we are working on establishing biosynthetic routes for other value-added compounds, such as alkaloids. We see the potential for using this strategy to discover new biosensors once we have established their production strains,” Ang shared.
The A*STAR researchers contributing to this research are affiliated with the Institute of Chemical and Engineering Sciences (ICES) and the Singapore Institute of Food and Biotechnology Innovation (SIFBI).