Engineered Saccharomyces cerevisiae for the De Novo Biosynthesis of (-)-Menthol

New insights into the roles of fungi and bacteria in the development of medicinal plant

BACKGROUND

The interaction between microorganisms and medicinal plants is a popular topic. Previous studies consistently reported that microorganisms were mainly considered pathogens or contaminants. However, with the development of microbial detection technology, it has been demonstrated that fungi and bacteria affect beneficially the medicinal plant production chain.

AIM OF REVIEW

Microorganisms greatly affect medicinal plants, with microbial biosynthesis a high regarded topic in medicinal plant-microbial interactions. However, it lacks a systematic review discussing this relationship. Current microbial detection technologies also have certain advantages and disadvantages, it is essential to compare the characteristics of various technologies.

KEY SCIENTIFIC CONCEPTS OF REVIEW

This review first illustrates the role of fungi and bacteria in various medicinal plant production procedures, discusses the development of microbial detection and identification technologies in recent years, and concludes with microbial biosynthesis of natural products. The relationship between fungi, bacteria, and medicinal plants is discussed comprehensively. We also propose a future research model and direction for further studies.

Recent Advances and Multiple Strategies of Monoterpenoid Overproduction in Saccharomyces cerevisiae and Yarrowia lipolytica

Monoterpenoids are an important subclass of terpenoids that play important roles in the energy, cosmetics, pharmaceuticals, and fragrances fields. With the development of biotechnology, microbial synthesis of monoterpenoids has received great attention. Yeasts such Saccharomyces cerevisiae and Yarrowia lipolytica are emerging as potential hosts for monoterpenoids production because of unique advantages including rapid growth cycles, mature gene editing tools, and clear genetic background. Recently, advancements in metabolic engineering and fermentation engineering have significantly enhanced the accumulation of monoterpenoids in cell factories. First, this review introduces the biosynthetic pathway of monoterpenoids and comprehensively summarizes the latest production strategies, which encompass enhancing precursor flux, modulating the expression of rate-limited enzymes, suppressing competitive pathway flux, mitigating cytotoxicity, optimizing substrate utilization, and refining the fermentation process. Subsequently, this review introduces four representative monoterpenoids. Finally, we outline the future prospects for efficient construction cell factories tailored for the production of monoterpenoids and other terpenoids.

Engineering Saccharomyces cerevisiae for synthesis of β-myrcene and (E)-β-ocimene

Monoterpenes are among the important natural plant terpenes. Monoterpenes usually have the characteristics of volatility and strong aroma. β-Myrcene and its isomer (E)-β-ocimene are typical acyclic monoterpenes. They are high-value monoterpenes that have been widely applied in foods, cosmetics, and medicines. However, large-scale commercial production of β-myrcene and (E)-β-ocimene is restricted by their production method that mainly involves extraction from plant essential oils. Currently, an alternative synthetic route utilizing an engineered microbial platform was proposed for effective production. This study used a Saccharomyces cerevisiae strain previously constructed for squalene production as the starting strain. Farnesyl diphosphate synthase (Erg20) expression was weakened by promoter replacement and screened for optimal myrcene synthase (MS) and ocimene synthase (OS) activities. In the resulting S. cerevisiae engineered for β-myrcene and (E)-β-ocimene synthesis, titers of β-myrcene and (E)-β-ocimene were enhanced by a fusion expressing a mutant Erg20* with the obtained monoterpene synthase and optimizing the added solvent in a two-phase fermentation system. Finally, by scaling up in a 5-L fermenter, 8.12 mg/L of β-myrcene was obtained, which was first reported in yeast, and 34.56 mg/L of (E)-β-ocimene was obtained, which is the highest reported to date. This study provides a new synthesis route for β-myrcene and (E)-β-ocimene.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13205-023-03818-2.

Advances in the dynamic control of metabolic pathways in Saccharomyces cerevisiae

The metabolic engineering of Saccharomyces cerevisiae has great potential for enhancing the production of high-value chemicals and recombinant proteins. Recent studies have demonstrated the effectiveness of dynamic regulation as a strategy for optimizing metabolic flux and improving production efficiency. In this review, we provide an overview of recent advancements in the dynamic regulation of S. cerevisiae metabolism. Here, we focused on the successful utilization of transcription factor (TF)-based biosensors within the dynamic regulatory network of S. cerevisiae. These biosensors are responsive to a wide range of endogenous and exogenous signals, including chemical inducers, light, temperature, cell density, intracellular metabolites, and stress. Additionally, we explored the potential of omics tools for the discovery of novel responsive promoters and their roles in fine-tuning metabolic networks. We also provide an outlook on the development trends in this field.

Efficient Synthesis of Limonene in Saccharomyces cerevisiae Using Combinatorial Metabolic Engineering Strategies

Limonene is a volatile monoterpene compound that is widely used in food additives, pharmaceutical products, fragrances, and toiletries. We herein attempted to perform efficient biosynthesis of limonene in Saccharomyces cerevisiae using systematic metabolic engineering strategies. First, we conducted de novo synthesis of limonene in S. cerevisiae and achieved a titer of 46.96 mg/L. Next, by dynamic inhibition of the competitive bypass of key metabolic branches regulated by ERG20 and optimization of the copy number of tLimS, a greater proportion of the metabolic flow was directed toward limonene synthesis, achieving a titer of 640.87 mg/L. Subsequently, we enhanced the acetyl-CoA and NADPH supply, which increased the limonene titer to 1097.43 mg/L. Then, we reconstructed the limonene synthesis pathway in the mitochondria. Dual regulation of cytoplasmic and mitochondrial metabolism further increased the limonene titer to 1586 mg/L. After optimization of the process of fed-batch fermentation, the limonene titer reached 2.63 g/L, the highest ever reported in S. cerevisiae.

High-Level Production of Patchoulol in Yarrowia lipolytica via Systematic Engineering Strategies

Patchoulol is an important sesquiterpene alcohol with a strong and lasting odor, which has led to prominent applications in perfumes and cosmetics. In this study, systematic metabolic engineering strategies were adopted to create an efficient yeast cell factory for patchoulol overproduction. First, a baseline strain was constructed by selecting a highly active patchoulol synthase. Subsequently, the mevalonate precursor pool was expanded to boost patchoulol synthesis. Moreover, a method for downregulating squalene synthesis based on Cu²⁺-repressible promoter was optimized, which significantly improved the patchoulol titer by 100.9% to 124 mg/L. In addition, a protein fusion strategy resulted in a final titer of 235 mg/L in shake flasks. Finally, 2.864 g/L patchoulol could be produced in a 5 L bioreactor, representing a remarkable 1684-fold increase compared to the baseline strain. To our knowledge, this is the highest patchoulol titer reported so far.