(-)-α-Bisabolol Production in Engineered Escherichia coli Expressing a Novel (-)-α-Bisabolol Synthase from the Globe Artichoke Cynara cardunculus var. Scolymus

Reprogramming Komagataella phaffii for a Robust Chassis toward Efficient De Novo Biosynthesis of (-)-α-Bisabolol

(-)-α-Bisabolol, a monocyclic susquiterpene alcohol, has been widely used in the fields of food, medicine, and biofuel. Recently, the rapid development of synthetic biology has offered a sustainable route for the production of (-)-α-bisabolol by microbial cell factories. Even though efficient biosynthesis of (-)-α-bisabolol has been achieved in Escherichia coli with the highest titer of 23.4 g/L, the possible infection risk by the bacteriophage makes E. coli unsuitable to act as the most robust chassis. Herein, we optimized the MVA pathway of Komagataella phaffii and fused farnesyl diphosphate synthase (ERG20), with bisabolol synthase for efficient production of (-)-α-bisabolol. Through the engineering of cofactor NADPH, molecular chaperone, and transcription factors, we obtained the robust (-)-α-bisabolol-producing strain, KB-30. Finally, the highly efficient production of (-)-α-bisabolol was achieved in a 5 L fed-batch fermenter, giving a titer of 32.8 g/L and a space-time yield of 283 mg/L/h. This work represents the highest production of (-)-α-bisabolol to date and provides new insights for efficient terpenoid biosynthesis.

Shaping up a Mevalonate Pathway in the E. coli-E. coli Coculture System for the Production of Sesquiterpenes

Sesquiterpenoids are one of the most diverse families of natural compounds with various bioactivities and functions. The introduction of an exogenous mevalonate pathway was recognized to be the proficient approach in Escherichia coli for sesquiterpene biosynthesis. It is challenging from the coordination of the pathway constituents to forge an active mevalonate pathway, especially the balance of mevalonate generation and consumption by the top and bottom portions of the mevalonate pathway. In this study, the pathway constituents were categorized to hierarchically assemble an active mevalonate pathway, which was optimized in a Kronecker product fashion and evaluated with host adaptation. Finally, the E. coli-E. coli coculture system was created to minimize the mevalonate accumulation. As a result, these engineering processes significantly maximized pathway efficiency and improved sesquiterpene biosynthesis, which suggests an easy-to-use approach to erect E. coli cell factories for sesquiterpene production.

Comparison between Indian and commercial chamomile essential oils: Chemical compositions, antioxidant activities and preventive effect on oxidation of Asian seabass visceral depot fat oil

Antioxidant properties of indigenous Indian (ICO) and commercial (CCO) chamomile essential oils (EOs) and their application in preventing lipid oxidation of fish oil were investigated. Solid-phase micro-extraction gas chromatography-mass spectrometry (SPME-GCMS) revealed dominant compounds to be α-bisabolol and chamazulene in ICO, while α-farnesene and δ-cadinene in CCO. Both EOs exhibited similar 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity and oxygen radical absorbance capacity (ORAC) values but ICO showed superior effect in β-carotene/linoleic system. When applied in Asian seabass visceral depot fat oil (SVDFO), ICO (400 mg/L) significantly reduced peroxide values after 15 days (30°C) and slightly lowered thiobarbituric acid reactive substances and anisidine values. ICO (400 mg/L) showed comparable efficacy in preventing the oxidation of polyunsaturated fatty acids (PUFAs) to 200 mg/L butylated hydroxytoluene (BHT) within 0-12 days. Fourier Transform Infrared (FTIR) analysis confirmed preservation of PUFA double bonds by ICO. Therefore, chamomile EOs, especially ICO, could prevent lipid peroxidation in PUFA-rich oils.

Constructing High-Yielding Serratia marcescens for (-)-α-Bisabolol Production Based on the Exogenous Haloarchaeal MVA Pathway and Endogenous Molecular Chaperones

(-)-α-Bisabolol exhibits analgesic, anti-inflammatory, and skin-soothing properties and is widely applied in the cosmetic and pharmaceutical industries. The use of plant essential oil distillation or chemical synthesis to produce (-)-α-bisabolol is both inefficient and unsustainable. Currently, the microbial production of (-)-α-bisabolol mainly relies on Escherichia coli and Saccharomyces cerevisiae as chassis strains; however, high concentrations of (-)-α-bisabolol have certain toxicity to the strain. This study uses synthetic biology and metabolic engineering strategies to redesign a solvent-tolerant Serratia marcescens for the efficient production of (-)-α-bisabolol. By introducing the Haloarchaea-type mevalonate (MVA) pathway and the (-)-α-bisabolol biosynthesis pathway, we successfully constructed a strain capable of producing (-)-α-bisabolol. The coexpression of the chaperone protein DnaK/J significantly enhanced the soluble expression of the (-)-α-bisabolol synthase, resulting in a 10% increase in (-)-α-bisabolol titer. Furthermore, knockout of the PhoA gene, which reduced the formation of the byproduct farnesol (FOH), further increased the (-)-α-bisabolol titer to 3.21 g/L. In a 5 L bioreactor, S. marcescens achieved a final (-)-α-bisabolol titer of 30.2 g/L, representing the highest titer reported to date. This research provides guidance for the production of (-)-α-bisabolol in nonmodel microorganisms without the requirement for induction.

Characterization and functional analysis of novel α-bisabolol synthase (MrBAS) promoter from Matricaria recutita

Matricaria recutita is widely used in industry and as a medicinal plant because it contains α-bisabolol. Alpha-bisabolol has broad application prospects due to its healthy function and medical value. The activity of the α-bisabolol synthase (MrBAS) promoter determines the expression of the MrBAS gene, which in turn influences the synthesis and accumulation of α-bisabolol. However, the activity and tissue specificity of the MrBAS promoter have not yet been characterized. In this study, a 1327-base pair (bp) region upstream of the MrBAS of the translation start site was cloned from the genome of M. recutita. MrBAS promoter sequence analysis revealed multiple light-responsive elements, and further dark treatment reduced α-bisabolol content in flowers. The α-bisabolol content and MrBAS expression levels in various flower tissues showed a strong correlation. The 5' deletion analysis revealed that the MrBAS promoter sequence could drive β-glucuronidase (GUS) gene expression in Nicotiana benthamiana leaves, with activity decreasing as the fragment shortened. Transgenic experiments demonstrated that the MrBAS promoter could specifically drive GUS gene expression in Arabidopsis anthers, pollen tubes, and petals. Thus, the MrBAS promoter has the potential to be a tool for directing transgene expression specifically in flower organs, offering new research avenues for cultivar development.

Development of a green Komagataella phaffii cell factory for sustainable production of plant-derived sesquiterpene (-)-α-bisabolol

(-)-α-Bisabolol is a plant-derived sesquiterpene derived from Eremanthus erythropappus, which can be used as a raw material in cosmetics and has anti-inflammatory function. In this study, we designed six mutation sites of the (-)-α-bisabolol synthase BOS using the plmDCA algorithm. Among these, the F324Y mutation demonstrated exceptional performance, increasing the product yield by 73 %. We constructed a de novo (-)-α-bisabolol biosynthesis pathways through systematic synthetic biology strategies, including the enzyme design of BOS, selection of different linkers in fusion expression, and optimization of the mevalonate pathway, weakening the branching metabolic flow and multi-copy strategies, the yield of (-)-α-bisabolol was significantly increased, which was nearly 35-fold higher than that of the original strain (2.03 mg/L). The engineered strain was capable of producing 69.7 mg/L in shake flasks. To the best of our knowledge, this is the first report on the biosynthesis of (-)-α-bisabolol in Komagataella phaffii, implying this is a robust cell factory for sustainable production of other terpenoids.

Engineered Methylococcus capsulatus Bath for efficient methane conversion to isoprene

Isoprene has numerous industrial applications, including rubber polymer and potential biofuel. Microbial methane-based isoprene production could be a cost-effective and environmentally benign process, owing to a reduced carbon footprint and economical utilization of methane. In this study, Methylococcus capsulatus Bath was engineered to produce isoprene from methane by introducing the exogenous mevalonate (MVA) pathway. Overexpression of MVA pathway enzymes and isoprene synthase from Populus trichocarpa under the control of a phenol-inducible promoter substantially improved isoprene production. M. capsulatus Bath was further engineered using a CRISPR-base editor to disrupt the expression of soluble methane monooxygenase (sMMO), which oxidizes isoprene to cause toxicity. Additionally, optimization of the metabolic flux in the MVA pathway and culture conditions increased isoprene production to 228.1 mg/L, the highest known titer for methanotroph-based isoprene production. The developed methanotroph could facilitate the efficient conversion of methane to isoprene, resulting in the sustainable production of value-added chemicals.

α-Bisabolol, a Dietary Sesquiterpene, Attenuates Doxorubicin-Induced Acute Cardiotoxicity in Rats by Inhibiting Cellular Signaling Pathways, Nrf2/Keap-1/HO-1, Akt/mTOR/GSK-3β, NF-κB/p38/MAPK, and NLRP3 Inflammasomes Regulating Oxidative Stress and Inflammatory Cascades

Cancer chemotherapy with doxorubicin (DOX) may have multiorgan toxicities including cardiotoxicity, and this is one of the major limitations of its clinical use. The present study aimed to evaluate the cardioprotective role of α-Bisabolol (BSB) in DOX-induced acute cardiotoxicity in rats and the underlying pharmacological and molecular mechanisms. DOX (12.5 mg/kg, single dose) was injected intraperitoneally into the rats for induction of acute cardiotoxicity. BSB was given orally to rats (25 mg/kg, p.o. twice daily) for a duration of five days. DOX administration induced cardiac dysfunction as evidenced by altered body weight, hemodynamics, and release of cardio-specific diagnostic markers. The occurrence of oxidative stress was evidenced by a significant decline in antioxidant defense along with a rise in lipid peroxidation and hyperlipidemia. Additionally, DOX also increased the levels and expression of proinflammatory cytokines and inflammatory mediators, as well as activated NF-κB/MAPK signaling in the heart, following alterations in the Nrf2/Keap-1/HO-1 and Akt/mTOR/GSK-3β signaling. DOX also perturbed NLRP3 inflammasome activation-mediated pyroptosis in the myocardium of rats. Furthermore, histopathological studies revealed cellular alterations in the myocardium. On the contrary, treatment with BSB has been observed to preserve the myocardium and restore all the cellular, molecular, and structural perturbations in the heart tissues of DOX-induced cardiotoxicity in rats. Results of the present study clearly demonstrate the protective role of BSB against DOX-induced cardiotoxicity, which is attributed to its potent antioxidant, anti-inflammatory, and antihyperlipidemic effects resulting from favorable modulation of numerous cellular signaling regulatory pathways, viz., Nrf2/Keap-1/HO-1, Akt/mTOR/GSK-3β, NF-κB/p38/MAPK, and NLRP3 inflammasomes, in countering the cascades of oxidative stress and inflammation. The observations suggest that BSB can be a promising agent or an adjuvant to limit the cardiac injury caused by DOX. Further studies including the role in tumor-bearing animals as well as regulatory toxicology are suggested.

Biosynthesis of monoterpenoid and sesquiterpenoid as natural flavors and fragrances

Terpenoids are a large class of plant-derived compounds, that constitute the main components of essential oils and are widely used as natural flavors and fragrances. The biosynthesis approach presents a promising alternative route in terpenoid production compared to plant extraction or chemical synthesis. In the past decade, the production of terpenoids using biotechnology has attracted broad attention from both academia and the industry. With the growing market of flavor and fragrance, the production of terpenoids directed by synthetic biology shows great potential in promoting future market prospects. Here, we reviewed the latest advances in terpenoid biosynthesis. The engineering strategies for biosynthetic terpenoids were systematically summarized from the enzyme, metabolic, and cellular dimensions. Additionally, we analyzed the key challenges from laboratory production to scalable production, such as key enzyme improvement, terpenoid toxicity, and volatility loss. To provide comprehensive technical guidance, we collected milestone examples of biosynthetic mono- and sesquiterpenoids, compared the current application status of chemical synthesis and biosynthesis in terpenoid production, and discussed the cost drivers based on the data of techno-economic assessment. It is expected to provide critical insights into developing translational research of terpenoid biomanufacturing.

Engineering Saccharomyces cerevisiae for enhanced (-)-α-bisabolol production

(-)-α-Bisabolol is naturally occurring in many plants and has great potential in health products and pharmaceuticals. However, the current extraction method from natural plants is unsustainable and cannot fulfil the increasing requirement. This study aimed to develop a sustainable strategy to enhance the biosynthesis of (-)-α-bisabolol by metabolic engineering. By introducing the heterologous gene MrBBS and weakening the competitive pathway gene ERG9, a de novo (-)-α-bisabolol biosynthesis strain was constructed that could produce 221.96 mg/L (-)-α-bisabolol. Two key genes for (-)-α-bisabolol biosynthesis, ERG20 and MrBBS, were fused by a flexible linker (GGGS)₃ under the GAL7 promoter control, and the titer was increased by 2.9-fold. Optimization of the mevalonic acid pathway and multi-copy integration further increased (-)-α-bisabolol production. To promote product efflux, overexpression of PDR15 led to an increase in extracellular production. Combined with the optimal strategy, (-)-α-bisabolol production in a 5 L bioreactor reached 7.02 g/L, which is the highest titer reported in yeast to date. This work provides a reference for the efficient production of (-)-α-bisabolol in yeast.

Disease resistance conferred by components of essential chrysanthemum oil and the epigenetic regulation of OsTPS1

The sesquiterpene alpha-bisabolol is the predominant active ingredient in essential oils that are highly valued in the cosmetics industry due to its wound healing, anti-inflammatory, and skin-soothing properties. Alpha-bisabolol was thought to be restricted to Compositae plants. Here we reveal that alpha-bisabolol is also synthesized in rice, a non-Compositae plant, where it acts as a novel sesquiterpene phytoalexin. Overexpressing the gene responsible for the biosynthesis of alpha-bisabolol, OsTPS1, conferred bacterial blight resistance in rice. Phylogenomic analyses revealed that alpha-bisabolol-synthesizing enzymes in rice and Compositae evolved independently. Further experiments demonstrated that the natural variation in the disease resistance level was associated with differential transcription of OsTPS1 due to polymorphisms in its promoter. We demonstrated that OsTPS1 was regulated at the epigenetic level by JMJ705 through the methyl jasmonate pathway. These data reveal the cross-family accumulation and regulatory mechanisms of alpha-bisabolol production.

Facile Production of (+)-Aristolochene and (+)-Bicyclogermacrene in Escherichia coli Using Newly Discovered Sesquiterpene Synthases from Penicillium expansum

Penicillium expansum, producer of a wide array of secondary metabolites, has the potential to be a source of new terpene synthases. In this work, a platform was constructed with Escherichia coli BL21(DE3) by enhancing its endogenous 2-methyl-d-erythritol-4-phosphate pathway to supply sufficient terpenoid precursors. Using this precursor-supplying platform, we discovered two sesquiterpene synthases from P. expansum: PeTS1, a new (+)-aristolochene synthase, and PeTS4, the first microbial (+)-bicyclogermacrene synthase. To enhance the sesquiterpene production by PeTS1, we employed a MBP fusion tag to improve the heterologous protein expression, resulting in the increase of aristolochene production up to 50 mg/L in a 72 h flask culture, which is the highest production reported to date. We also realized the first biosynthesis of (+)-bicyclogermacrene, achieving 188 mg/L in 72 h. This work highlights the great potential of this microbial platform for the discovery of new terpene synthases and opens new ways for the bioproduction of other valuable terpenoids.

YALIcloneNHEJ: An Efficient Modular Cloning Toolkit for NHEJ Integration of Multigene Pathway and Terpenoid Production in Yarrowia lipolytica

Non-homologous end-joining (NHEJ)-mediated random integration in Yarrowia lipolytica has been demonstrated to be an effective strategy for screening hyperproducer strains. However, there was no multigene assembly method applied for NHEJ integration, which made it challenging to construct and integrate metabolic pathways. In this study, a Golden Gate modular cloning system (YALIcloneNHEJ) was established to develop a robust DNA assembly platform in Y. lipolytica. By optimizing key factors, including the amounts of ligase and the reaction cycles, the assembly efficiency of 4, 7, and 10 fragments reached up to 90, 75, and 50%, respectively. This YALIcloneNHEJ system was subsequently applied for the overproduction of the sesquiterpene (-)-α-bisabolol by constructing a biosynthesis route and enhancing the flux in the mevalonate pathway. The resulting strain produced 4.4 g/L (-)-α-bisabolol, the highest titer reported in yeast to date. Our study expands the toolbox of metabolic engineering and is expected to enable a highly efficient production of various terpenoids.

Characterization of γ-Cadinene Enzymes in Ganoderma lucidum and Ganoderma sinensis from Basidiomycetes Provides Insight into the Identification of Terpenoid Synthases

Enzymes boost protein engineering, directed evolution, and the biochemical industry and are also the cornerstone of metabolic engineering. Basidiomycetes are known to produce a large variety of terpenoids with unique structures. However, basidiomycetous terpene synthases remain largely untapped. Therefore, we provide a modeling method to obtain specific terpene synthases. Aided by bioinformatics analysis, three γ-cadinene enzymes from Ganoderma lucidum and Ganoderma sinensis were accurately predicted and identified experimentally. Based on the highly conserved amino motifs of the characterized γ-cadinene enzymes, the enzyme was reassembled as model 1. Using this model as a template, 67 homologous sequences of the γ-cadinene enzyme were screened from the National Center for Biotechnology Information (NCBI). According to the 67 sequences, the same gene structure, and similar conserved motifs to model 1, the γ-cadinene enzyme model was further improved by the same construction method and renamed as model 2. The results of bioinformatics analysis show that the conservative regions of models 1 and 2 are highly similar. In addition, five of these sequences were verified, 100% of which were γ-cadinene enzymes. The accuracy of the prediction ability of the γ-cadinene enzyme model was proven. In the same way, we also reanalyzed the identified Δ6-protoilludene enzymes in fungi and (-)-α-bisabolol enzymes in plants, all of which have their own unique conserved motifs. Our research method is expected to be used to study other terpenoid synthases with a similar or the same function in basidiomycetes, ascomycetes, bacteria, and plants and to provide rich enzyme resources.