# Fermentation Strategies for Production of Pharmaceutical Ternenoids in Engineered Yeast
###### Abstract  
Ternenoids, also known as isoprenoids, are a broad and diverse class of plant natural products with significant industrial and pharmaceutical importance. Many of these natural products have antitumor, anti-inflammatory, antibacterial, antiviral, and antimalarial effects, support transdermal absorption, prevent and treat cardiovascular diseases, and have hypoglycemic activities. Production of these compounds are generally carried out through extraction from their natural sources or chemical synthesis. However, these processes are generally unsustainable, produce low yield, and result in wasting of substantial resources, most of them limited. Microbial production of terpenoids provides a sustainable and environment-friendly alternative. In recent years, the yeast _Saccharomyces cerevisiae_ has become a suitable cell factory for industrial terpenoid biosynthesis due to developments in omics studies (genomics, transcriptomics, metabolomics, proteomics), and mathematical modeling. Besides that, fermentation development has a significant importance on achieving high titer, yield, and productivity (TYP) of these compounds. Up to now, there have been many studies and reviews reporting metabolic strategies for terpene biosynthesis. However, fermentation strategies have not been yet comprehensively discussed in the literature. This review summarizes recent studies of recombinant production of pharmaceuticals import terpenoids by engineered yeast, _S. cerevisiae_, with special focus on fermentation strategies to increase TYP in order to meet industrial demands to feed the pharmaceutical market. Factors affecting recombinant terpenoids production are reviewed (strain design and fermentation parameters) and types of fermentation process (batch, fed-batch, and continuous) are discussed. terpenoids; _S. cerevisiae_; pharmaceutics; fermentation; fed-batch +
Footnote †: 26 March 2021  
onate (MVA) or 2-C-methyl-d-erythtitol 4-phosphate (MEP) (which is also known as the non-mevalonate) pathway [2; 3]. Through the condensation reactions of these units, several large and more complex compounds are produced. According to the number of C5 isoprene units, terpenoids are mainly classified in hemicreponoid (C5), monoterepenoid (C10), sesquiterpenoid (C15), diterpenoid (C20), triterpenoid (C30), tetraterpenoid (C40), and polytrepenoid (C > 40) [2; 3; 6]. terpenoids are mostly formed through continuous addition of head to tail manner of building blocks, which are isoprene diphosphate (IPP) and dimethylallyl diphosphate (DMAPP). For instance, the precursor of monotereponids, geranyl diphosphate (GPP), is produced by head to tail condensation of these two building blocks. Later, addition of IPP leads to the formation of farnesyl diphosphate (FPP) and geranylgeranyl diphosphate (GGPP), which are precursors of sesquiterpenoid and diterpenoid. On the other hand, head to head condensation of two molecules of FPP and GGPP, respectively, forms squalene and phytoene, the precursors of triterpen and tetraterpenoid [6; 7] (Figure 1). Furthermore, these precursors are exposed to oxidation, by cytochrome P450 oxygenases, and glycosylation, by glycosyltransferases to form various terpenoids. In addition, premyltransferases concatenates isoprene-derived precursors to fatty acid-derived precursor to synthase complex terpenoids or meroterpenoids, which consist of the medically important compounds, canabinoids [2]. From early ancient times up to now, terpenoids have been playing important roles in many medical treatments as pharmaceuticals with diverse biomedical activities, such as antimalarial, anticancer, anti-inflammatory, antibacterial, antiviral, hypoglycemic, preventing and treating cardiovascular diseases, and promoting the transdermal absorption. Figure 1: The condensation reactions of terpenoid biosynthesis: (**A**) Head to tail condensation and (**B**) Tail to tail condensation (Adapted from [7]). Besides that, they can have insecticidal, immunomodulatory, antioxidant, antiaging, and neuroprotective effects [2; 3; 8; 9].