Polyphenols are plant secondary metabolites with diverse biological and potential therapeutic activities such as antioxidant, anti-inflammatory and anticancer, among others. However, their extraction from the native plants is not enough to satisfy the increasing demand for this type of compounds. The development of microbial cell factories to effectively produce polyphenols may represent the most attractive solution to overcome this limitation and produce high amounts of these bioactive molecules. With the advances in the synthetic biology field, the development of efficient microbial cell factories has become easier, largely due to the development of the molecular biology techniques and by the identification of novel isoenzymes in plants or simpler organisms to construct the heterologous pathways. Furthermore, efforts have been made to make the process more profitable through improvements in the host chassis. In this review, advances in the production of polyphenols by genetically engineered Saccharomyces cerevisiae as well as by synthetic biology and metabolic engineering approaches to improve the production of these compounds at industrial settings are discussed.

Saccharomyces cerevisiae has been for a long time a common model for fundamental biological studies and a popular biotechnological engineering platform to produce chemicals, fuels, and pharmaceuticals due to its peculiar characteristics. Both lines of research require an effective editing of the native genetic elements or the inclusion of heterologous pathways into the yeast genome. Although S. cerevisiae is a well-known host with several molecular biology tools available, a more precise tool is still needed. The clustered, regularly interspaced, short palindromic repeats–associated Cas9 (CRISPR-Cas9) system is a current, widespread genome editing tool. The implementation of a reprogrammable, precise, and specific method, such as CRISPR-Cas9, to edit the S. cerevisiae genome has revolutionized laboratory practices. Herein, we describe and discuss some applications of the CRISPR-Cas9 system in S. cerevisiae from simple gene knockouts to more complex processes such as artificial heterologous pathway integration, transcriptional regulation, or tolerance engineering.

Zymomonas mobilis is a well-recognized ethanologenic bacterium with outstanding characteristics which make it a promising platform for the biotechnological production of relevant building blocks and fine chemicals compounds. In the last years, research has been focused on the physiological, genetic, and metabolic engineering strategies aiming at expanding Z. mobilis ability to metabolize lignocellulosic substrates toward biofuel production. With the expansion of the Z. mobilis molecular and computational modeling toolbox, the potential of this bacterium as a cell factory has been thoroughly explored. The number of genomic, transcriptomic, proteomic, and fluxomic data that is becoming available for this bacterium has increased. For this reason, in the forthcoming years, systems biology is expected to continue driving the improvement of Z. mobilis for current and emergent biotechnological applications. While the existing molecular toolbox allowed the creation of stable Z. mobilis strains with improved traits for pinpointed biotechnological applications, the development of new and more flexible tools is crucial to boost the engineering capabilities of this bacterium. Novel genetic toolkits based on the CRISPR-Cas9 system and recombineering have been recently used for the metabolic engineering of Z. mobilis. However, they are mostly at the proof-of-concept stage and need to be further improved. Graphical Abstract

Curcumin, a natural polyphenol derived from turmeric, has attracted immense interest due to its diverse pharmacological properties. Traditional extraction methods from Curcuma longa plants present limitations in meeting the growing demand for this bioactive compound, giving significance to its production by genetically modified microorganisms. Herein, we have developed an engineered Saccharomyces cerevisiae to produce curcumin from glucose. A pathway composed of the 4-hydroxyphenylacetate 3-monooxygenase oxygenase complex from Pseudomonas aeruginosa and Salmonella enterica, caffeic acid O-methyltransferase from Arabidopsis thaliana, feruloyl-CoA synthetase from Pseudomonas paucimobilis, and diketide-CoA synthase and curcumin synthase from C. longa was introduced in a p-coumaric acid overproducing S. cerevisiae strain. This strain produced 240.1 ± 15.1 μg/L of curcumin. Following optimization of phenylpropanoids conversion, a strain capable of producing 4.2 ± 0.6 mg/L was obtained. This study reports for the first time the successful de novo production of curcumin in S. cerevisiae.