Shame on yeast: challenges and bottlenecks to engineer red anthocyanin-producing yeasts

The relative abundance of anthocyanins in the human diet and their potency against a range of chronic diseaseshave made them the subject of intense research in experimental and preventive medicine. However, the limitedrange of anthocyanins commercially available and the expense of pure preparations mean that most research isdone with crude extracts of plants which are not standardised with respect to the particular anthocyanins theycontain, nor the amounts of each anthocyanin in the extract. Beside the unique plant cell cultures recentlydeveloped for the stable production of a variety of anthocyanins (www.anthoplus.com) novel procedures forsustainable, high level production of diverse natural products in heterologous hosts like microorganisms show ahigh yield and can be up scaled to industrial production. Although all major genes coding for enzymes for theanthocyanins pathway were successfully expressed in yeast so far the multistep combinatorial synthesis ofanthocyanins was only described for bacterial system starting from flavanone stage [1]. The “red yeast” projectintensely focuses on strategies to genetically modify yeast (Saccharomyces cerevisiae) as innovative host for thecombinatorial synthesis of various anthocyanins starting from a recently developed naringenin-producing strain[2]. Genetic modification strategies for heterologous gene expression and host bioengineering will be carried out.Furthermore, challenges and bottlenecks as native degrading and/or competing proteins (e.g. ?-glucosidases) andthe described side activities of anthocyanin pathway proteins need to be overcome [1,3-4]. Finally, this strategiesaim to establish a robust pre-industrial production system for new, pure anthocyanins with different side chaindecorations.