Production of methoxylated flavonoids in yeast using ring A hydroxylases and flavonoid O-methyltransferases from sweet basil
Numerous methoxylated flavonoids exhibit pronounced bioactivities. Their biotechnological production and diversification are therefore of interest to pharmaceutical and nutraceutical industries. We used a set of enzymes from sweet basil (Ocimum basilicum) to construct five strains of Saccharomyces cerevisiae producing 8- and/or 6-substituted, methoxylated flavones from their natural precursor apigenin. After identifying several growth parameters affecting the overall yields and flux, we applied optimized conditions and explored the ability of the generated strains to utilize alternative substrates. The yeast cells produced substantial amounts of 6-hydroxylated, methylated derivatives of naringenin and luteolin while the corresponding derivatives of flavonol kaempferol were only detected in trace amounts. Analysis of the intermediates and by-products of the different bioconversions suggested that the substrate specificity of both the hydroxylases and the flavonoid O-methyltransferases is imposing barriers on yields obtained with alternative substrates and highlighted steps that appear to represent bottlenecks en route to increasing the strains’ efficiencies. Additionally, analysis of flavonoid localization during fermentation revealed unequal distribution with strong intracellular accumulation of a number of methylated flavonoids and extracellular enrichment of several pathway intermediates. This work establishes a platform for the production of complex methoxylated flavonoids and discusses strategies for its improvement.
Keywords(Poly)methoxylated flavonoids Saccharomyces cerevisiae Biotechnology Biodiversification Ring A hydroxylase Flavonoid O-methyltransferase
AB would like to thank Dr. G. O. Berim (SUNY at Buffalo, NY) for help with statistical analysis.
This work was in part supported by the US Department of Energy Biological and Environmental Research Program (grant DE-SC0001728 to D.R.G.).
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
This article does not contain any studies with human participants or animals
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