Production of 11-Oxo-β-Amyrin in Saccharomyces cerevisiae at High Efficiency by Fine-Tuning the Expression Ratio of CYP450:CPR

Multiplexed engineering of cytochrome P450 enzymes for promoting terpenoid synthesis in Saccharomyces cerevisiae cell factories: A review

Terpenoids, also known as isoprenoids, represent the largest and most structurally diverse family of natural products, and their biosynthesis is closely related to cytochrome P450 enzymes (P450s). Given the limitations of direct extraction from natural resources, such as low productivity and environmental concerns, heterologous expression of P450s in microbial cell factories has emerged as a promising, efficient, and sustainable strategy for terpenoid production. The yeast expression system is a preferred selection for terpenoid synthesis because of its inner membrane system, which is required for eukaryotic P450 expression, and the inherent mevalonate pathway providing precursors for terpenoid synthesis. In this review, we discuss the advanced strategies used to enhance the local enzyme concentration and catalytic properties of P450s in Saccharomyces cerevisiae, with a focus on recent developments in metabolic and protein engineering. Expression enhancement and subcellular compartmentalization are specifically employed to increase the local enzyme concentration, whereas cofactor, redox partner, and enzyme engineering are utilized to improve the catalytic efficiency and substrate specificity of P450s. Subsequently, we discuss the application of P450s for the pathway engineering of terpenoid synthesis and whole-cell biotransformation, which are profitable for the industrial application of P450s in S. cerevisiae chassis. Finally, we explore the potential of using computational and artificial intelligence technologies to rationally design and construct high-performance cell factories, which offer promising pathways for future terpenoid biosynthesis.

De Novo Biosynthesis of Antidepressant Psilocybin in Escherichia coli

Psilocybin, a tryptamine-derived alkaloid, has been granted Breakthrough Therapy designation by the U.S. FDA for treatment-resistant depression, underscoring its clinical importance. Therefore, sustainable and economic production is urgently needed. Manufacturing of psilocybin in Escherichia coli has drawn great attention. However, due to the low expression and activity of the eukaryotic cytochrome P450 enzyme PsiH in the psilocybin biosynthetic pathway, de novo synthesis of psilocybin in prokaryotic cells has been hampered. To overcome this dilemma, we herein demonstrated de novo synthesis of psilocybin in E. coli by constructing PsiH variants with N-terminal domain modifications and expressing the entire biosynthetic pathway at a concordantly low temperature. Improving the supply of precursor and engineering the P450 electron transfer chain resulted in a 33-fold increase in the titre of norbaeocystin (105.3 mg/L), a key intermediate of psilocybin biosynthesis, and a 17-fold increase in the titre of psilocybin (14 mg/L). Further enhancement of psilocybin production was achieved by converting norbaeocystin to psilocybin by overexpressing an extra copy of the methyltransferase gene psiM. Finally, 79.4 mg/L of psilocybin was produced by optimising flask fermentation conditions, a 100-fold improvement over the starting strain. Our work demonstrates the successful fungal P450 engineering to improve the catalytic activity in E. coli and will advance the sustainable production of the important antidepressant psilocybin in prokaryotic microbial cells.

Biosynthesis and metabolic engineering of natural sweeteners

Natural sweeteners have attracted widespread attention because they are eco-friendly, healthy, low in calories, and tasty. The demand for natural sweeteners is increasing together with the popularity of green, low-carbon, sustainable development. With the development of synthetic biology, microbial cell factories have emerged as an effective method to produce large amounts of natural sweeteners. This technology has significantly progressed in recent years. This review summarizes the pathways and the enzymes related to the biosynthesis of natural sweeteners, such as mogrosides, steviol glycosides, glycyrrhizin, glycyrrhetinic acid, phlorizin, trilobatin, erythritol, sorbitol, mannitol, thaumatin, monellin, and brazzein. Moreover, it focuses on the research about the microbial production of these natural sweeteners using synthetic biology methods, aiming to provide a reference for future research on the production of natural sweeteners.

Discovery, Biomanufacture, and Derivatization of Licorice Triterpenoids

Triterpenoids are the major active constituents of licorice, a well-known traditional medicinal herb. Licorice triterpenoids, represented by glycyrrhizin and glycyrrhetic acid, have a high structural diversity and are excellent lead compounds for the development of potent pharmaceuticals. However, their further application can be limited by insufficient activities, low bioavailability, and the presence of side effects, as well as the inefficiency of traditional plant extraction processes for compound production. To address these issues, researchers are focusing on rare triterpenoid components in the genus Glycyrrhiza and developing derivatives to preserve or enhance the original physiological activities with improved bioavailability and reduced side effects. At the same time, synthetic biology offers opportunities to shorten the production cycle, create eco-friendly manufacturing processes, and reduce the cost of producing licorice triterpenoids. Although much progress has been achieved in this field in recent years, there is still a lack of a comprehensive review to summarize the overall characteristics of licorice triterpenoids rather than glycyrrhizin and glycyrrhetinic acid. Based on this, our review comprehensively outlines the structures, origins, and pharmacological activities of licorice triterpenoids and predicts their pharmacological activities using the drugCIPHER algorithm. Furthermore, this paper reviews the advances and strategies for the biomanufacturing of licorice triterpenoids using synthetic biology methods and outlines the perspectives and structure-activity relationships for the derivatization of licorice triterpenoids. This review provides new insights into the discovery and synthesis of pharmaceuticals derived from natural triterpenes.

Herbal Multiomics Provide Insights into Gene Discovery and Bioproduction of Triterpenoids by Engineered Microbes

Triterpenoids are natural products found in plants that exhibit industrial and agricultural importance. Triterpenoids are typically synthesized through two main pathways: the mevalonate (MVA) and methylerythritol 4-phosphate (MEP) pathways. They then undergo structural diversification with the help of squalene cyclases (OSCs), cytochrome P450 monooxygenases (P450s), UDP glycosyltransferases (UGTs), and acyltransferases (ATs). Advances in multiomics technologies for herbal plants have led to the identification of novel triterpenoid biosynthetic pathways. The application of various analytical techniques facilitates the qualitative and quantitative analysis of triterpenoids. Progress in synthetic biology and metabolic engineering has also facilitated the heterologous production of triterpenoids in microorganisms, such as Escherichia coli and Saccharomyces cerevisiae. This review summarizes recent advances in biotechnological approaches aimed at elucidating the complex pathway of triterpenoid biosynthesis. It also discusses the metabolic engineering strategies employed to increase the level of triterpenoid production in chassis cells.

Heterologous Biosynthesis of Terpenoids in Saccharomyces cerevisiae

Terpenoids are widely distributed in nature and have various applications in healthcare products, pharmaceuticals, and fragrances. Despite the significant potential that terpenoids possess, traditional production methods, such as plant extraction and chemical synthesis, face challenges in meeting current market demand. With the advancement of synthetic biology and metabolic engineering, it becomes feasible to construct efficient microbial cell factories for large-scale production of terpenoids. This article primarily centers on the heterologous expression of terpenoids in Saccharomyces cerevisiae, detailing the expression of terpenoid biosynthesis pathways through the utilization of cellular microcompartments, strategies for the efficient expression of key P450 enzymes in the synthesis pathway, and the regulation and optimization of host metabolism to enhance flux to terpenoids synthesis. Additionally, we analyze current challenges and propose solutions to further refine yeast chassis for more effective terpenoids production.

Debottlenecking cytochrome P450-dependent metabolic pathways for the biosynthesis of commercial natural products

Covering: 2016 to the end of 2024This highlight article aims to provide a perspective on the challenges that novel biotechnological processes face in the biomanufacturing of natural products (NPs) whose biosynthesis pathways rely on cytochrome P450 monooxygenases. This enzyme superfamily is one of the most versatile in the biosynthesis of a plethora of NPs finding use across the food, nutrition, medicine, chemical and cosmetics industries. These enzymes often exhibit excellent regio- and stereoselectivity, but they can suffer from low activity and instability, which are serious issues impairing the development of high performing bioprocesses. We start with a brief introduction to industrial biotechnology and the importance of looking for alternative means for producing NPs independently from unsustainable fossil fuels or plant extractions. We then discuss the challenges and implemented solutions during the development of commercial NP processes focusing on the P450-dependent steps primarily in yeast cell factories. Our main focus is to highlight the challenges often encountered when utilizing P450-dependent NP pathways, and how protein engineering can be used for debottlenecking them. Finally, we briefly touch upon the importance of artificial intelligence and machine learning for guiding engineering efforts.

Glycyrrhiza, a commonly used medicinal herb: Review of species classification, pharmacology, active ingredient biosynthesis, and synthetic biology

BACKGROUND

Licorice is extensively and globally utilized as a medicinal herb and is one of the traditional Chinese herbal medicines with valuable pharmacological effects. Its therapeutic components primarily reside within its roots and rhizomes, classifying it as a tonifying herb. As more active ingredients in licorice are unearthed and characterized, licorice germplasm resources are gaining more and more recognition. However, due to the excessive exploitation of wild licorice resources, the degrading germplasm reserves fail to meet the requirements of chemical extraction and clinical application.

AIM OF REVIEW

This article presents a comprehensive review of the classification and phylogenetic relationships of species in genus Glycyrrhiza, types of active components and their pharmacological activities, licorice omics, biosynthetic pathways of active compounds in licorice, and metabolic engineering. It aims to offer a unique and comprehensive perspective on Glycyrrhiza, integrating knowledge from diverse fields to offer a comprehensive understanding of this genus. It will serve as a valuable resource and provide a solid foundation for future research and development in the molecular breeding and synthetic biology fields of Glycyrrhiza.

KEY SCIENTIFIC CONCEPTS OF REVIEW

Licorice has an abundance of active constituents, primarily triterpenoids, flavonoids, and polysaccharides. Modern pharmacological research unveiled its multifaceted effects encompassing anti-inflammatory, analgesic, anticancer, antiviral, antioxidant, and hepatoprotective activities. Many resources of Glycyrrhiza species remain largely untapped, and multiomic studies of the Glycyrrhiza lineage are expected to facilitate new discoveries in the fields of medicine and human health. Therefore, strategies for breeding high-yield licorice plants and developing effective biosynthesis methods for bioactive compounds will provide valuable insights into resource conservation and drug development. Metabolic engineering and microorganism-based green production provide alternative strategies to improve the production efficiency of natural products.

De novo biosynthesis of betulinic acid in engineered Saccharomyces cerevisiae

Betulinic acid (BA) is a lupinane-type pentacyclic triterpenoid natural product derived from lupeol that has favorable anti-inflammatory and anti-tumor activities. Currently, BA is mainly produced via botanical extraction, which significantly limits its widespread use. In this study, we investigated the de novo synthesis of BA in Saccharomyces cerevisiae, and to facilitate the synthesis and storage of hydrophobic BA, we adopted a dual-engineering strategy involving peroxisomes and lipid droplets to construct the BA biosynthetic pathway. By expressing Betula platyphylla-derived lupeol C-28 oxidase (BPLO) and Arabidopsis-derived ATR1, we succeeded in developing a BA-producing strain and following multiple expression optimizations of the linker between BPLO and ATR1, the BA titer reached 77.53 mg/L in shake flasks and subsequently reached 205.74 mg/L via fed-batch fermentation in a 5-L bioreactor. In this study, we developed a feasible approach for the de novo synthesis of BA and its direct precursor lupeol in engineered S. cerevisiae.

Establishing cell suitability for high-level production of licorice triterpenoids in yeast

Yeast has been an indispensable host for synthesizing complex plant-derived natural compounds, yet the yields remained largely constrained. This limitation mainly arises from overlooking the importance of cell and pathway suitability during the optimization of enzymes and pathways. Herein, beyond conventional enzyme engineering, we dissected metabolic suitability with a framework for simultaneously augmenting cofactors and carbon flux to enhance the biosynthesis of heterogenous triterpenoids. We further developed phospholipid microenvironment engineering strategies, dramatically improving yeast's suitability for the high performance of endoplasmic reticulum (ER)-localized, rate-limiting plant P450s. Combining metabolic and microenvironment suitability by manipulating only three genes, NHMGR (NADH-dependent HMG-CoA reductase), SIP4 (a DNA-binding transcription factor)and GPP1 (Glycerol-1-phosphate phosphohydrolase 1), we enabled the high-level production of 4.92 g/L rare licorice triterpenoids derived from consecutive oxidation of β-amyrin by two P450 enzymes after fermentation optimization. This production holds substantial commercial value, highlighting the critical role of establishing cell suitability in enhancing triterpenoid biosynthesis and offering a versatile framework applicable to various plant natural product biosynthetic pathways.

Application of multiple strategies to enhance oleanolic acid biosynthesis by engineered Saccharomyces cerevisiae

Oleanolic acid and its derivatives are widely used in the pharmaceutical, agricultural, cosmetic and food industries. Previous studies have shown that oleanolic acid production levels in engineered cell factories are low, which is why oleanolic acid is still widely extracted from traditional medicinal plants. To construct a highly efficient oleanolic acid production strain, rate-limiting steps were regulated by inducible promoters and the expression of key genes in the oleanolic acid synthetic pathway was enhanced. Subsequently, precursor pool expansion, pathway refactoring and diploid construction were considered to harmonize cell growth and oleanolic acid production. The multi-strategy combination promoted oleanolic acid production of up to 4.07 g/L in a 100 L bioreactor, which was the highest level reported.

Recent advances in triterpenoid pathway elucidation and engineering

Triterpenoids are among the most assorted class of specialized metabolites found in all the taxa of living organisms. Triterpenoids are the leading active ingredients sourced from plant species and are utilized in pharmaceutical and cosmetic industries. The triterpenoid precursor 2,3-oxidosqualene, which is biosynthesized via the mevalonate (MVA) pathway is structurally diversified by the oxidosqualene cyclases (OSCs) and other scaffold-decorating enzymes such as cytochrome P450 monooxygenases (P450s), UDP-glycosyltransferases (UGTs) and acyltransferases (ATs). A majority of the bioactive triterpenoids are harvested from the native hosts using the traditional methods of extraction and occasionally semi-synthesized. These methods of supply are time-consuming and do not often align with sustainability goals. Recent advancements in metabolic engineering and synthetic biology have shown prospects for the green routes of triterpenoid pathway reconstruction in heterologous hosts such as Escherichia coli, Saccharomyces cerevisiae and Nicotiana benthamiana, which appear to be quite promising and might lead to the development of alternative source of triterpenoids. The present review describes the biotechnological strategies used to elucidate complex biosynthetic pathways and to understand their regulation and also discusses how the advances in triterpenoid pathway engineering might aid in the scale-up of triterpenoid production in engineered hosts.