Complete Biotransformation of Protopanaxadiol-Type Ginsenosides to 20- O-β-Glucopyranosyl-20( S)-protopanaxadiol Using a Novel and Thermostable β-Glucosidase

The transformation pathways and optimization of conditions for preparation minor ginsenosides from Panax notoginseng root by the fungus Aspergillus tubingensis

Minor ginsenosides exhibit enhanced pharmacological effects in comparison to the major ginsenosides. However, the natural content of minor ginsenosides in plants is typically insufficient to satisfy clinical demand. Therefore, we investigated the biotransformation of the major ginsenosides in Panax notoginseng to minor ginsenosides by the fungus Aspergillus tubingensis. The transformation products were analyzed using TLC, HPLC, and LC-MS techniques to propose the biotransformation pathways of major ginsenosides. A. tubingensis was found to transform the main ginsenosides into 15 minor ginsenosides, inculding (R/S)-Rg3, Rk1, Rg5, F2, (R/S)-Rh1, Rk3, Rh4, (R/S)-Rg2, F4, Rg6 and (R/S)-R2. The transformation reactions encompassed isomerization, hydrolysis and dehydration. We have also optimized the reaction temperature and pH for the crude enzyme extracted from this fungus, which has a molecular weight of 66 kDa. Based on our current knowledge, this transformative characteristic of A. tubingensis was initially documented for the concurrent transformation of PPD and PPT type saponins in P. notoginseng. This method of preparing minor saponins will be valuable for the development of P. notoginseng as a traditional medicinal material.

Comparison of the Transformation Ability of the Major Saponins in Panax notoginseng by Penicillum fimorum Enzyme and Commercial β-glucosidase

Ginsenosides with less sugar groups, which are called minor ginsenosides, might have a greater pharmacological activity and better adsorptive ability, but their content in nature is extremely low. In this study, a strain of Penicillium fimorum with a strong saponin transformation ability was isolated from fresh Gastrodia elata. A comparative biotransformation experiment of the major saponins from Panax notoginseng root were conducted using crude enzymes from P. fimorum and commercial β-glucosidase to produce minor ginsenosides. Specifically, the crude enzyme from P. fimorum was able to transform the major saponins from P. notoginseng root into 13 minor saponins in 72 h, while commercial β-glucosidase was able to transform the same major saponins into 15 minor saponins in 72 h. The most significant difference between these two enzymes is their ability to transform Rb1. To the best of our knowledge, the biotransformation ability of crude enzymes from P. fimorum is reported here for the first time. These two enzymes have the potential to improve the economic value of P. notoginseng root and expand the methods for preparing minor saponins by transforming major saponins in the total saponins of P. notoginseng root.

Rare ginsenosides: A unique perspective of ginseng research

BACKGROUND

Rare ginsenosides (Rg3, Rh2, C-K, etc.) refer to a group of dammarane triterpenoids that exist in low natural abundance, mostly produced by deglycosylation or side chain modification via physicochemical processing or metabolic transformation in gut, and last but not least, exhibited potent biological activity comparing to the primary ginsenosides, which lead to a high concern in both the research and development of ginseng and ginsenoside-related nutraceutical and natural products. Nevertheless, a comprehensive review on these promising compounds is not available yet.

AIM OF REVIEW

In this review, recent advances of Rare ginsenosides (RGs) were summarized dealing with the structurally diverse characteristics, traditional usage, drug discovery situation, clinical application, pharmacological effects and the underlying mechanisms, structure-activity relationship, toxicity, the stereochemistry properties, and production strategies.

KEY SCIENTIFIC CONCEPTS OF REVIEW

A total of 144 RGs with diverse skeletons and bioactivities were isolated from Panax species. RGs acted as natural ligands on some specific receptors, such as bile acid receptors, steroid hormone receptors, and adenosine diphosphate (ADP) receptors. The RGs showed promising bioactivities including immunoregulatory and adaptogen-like effect, anti-aging effect, anti-tumor effect, as well as their effects on cardiovascular and cerebrovascular system, central nervous system, obesity and diabetes, and interaction with gut microbiota. Clinical trials indicated the potential of RGs, while high quality data remains inadequate, and no obvious side effects was found. The stereochemistry properties induced by deglycosylation at C (20) were also addressed including pharmacodynamics behaviors, together with the state-of-art analytical strategies for the identification of saponin stereoisomers. Finally, the batch preparation of targeted RGs by designated strategies including heating or acid/ alkaline-assisted processes, and enzymatic biotransformation and biosynthesis were discussed. Hopefully, the present review can provide more clues for the extensive understanding and future in-depth research and development of RGs, originated from the worldwide well recognized ginseng plants.

Improving the bioactivity of water-soluble alfalfa saponins using biotransformation

Medicago sativa L. is gaining attention as a sustainable plant-based food protein. Alfalfa saponins (ASs) typically exist in a glycosylated form in nature, which has poor cell membrane permeability, while the deglycosylated saponins may show better bioactivity. The AS was deglycosylated by β-glucosidase from Aspergillus niger, and the chemical structures and biological activities, including in vivo assays, of AS and deglycosylated AS (DAS) were determined. The results showed that the half maximal inhibitory concentration for 2,2-diphenyl-1-picrylhydrazyl inhibition of DAS was 29.5 µg/mL, demonstrating a significantly higher reducing capacity compared to AS (p < 0.05). The DAS induced 33.8% antibacterial activity against Escherichia coli and enhanced the proliferation of human airway epithelial cells (BEAS-2B) at a concentration of 125 µg/mL. In vivo experiments on C57BL/6 mice fed a high-fat diet demonstrated that high-level DAS treatment produced significantly greater hypolipidemic effects compared to AS (p < 0.05). Thus, the AS can be deglycosylated, which leads to an improvement in biological activity, particularly since the DAS exhibits significantly enhanced hypolipidemic activity. PRACTICAL APPLICATION: Alfalfa saponins were deglycosylated by β-glucosidase from Aspergillus niger, which contributed to increased bioactivity, particularly its hypolipidemic activity.

Advancements in enzymatic biotransformation and bioactivities of rare ginsenosides: A review

Ginsenoside, the principal active constituent of ginseng, exhibits enhanced bioavailability and medicinal efficacy in rare ginsenosides compared to major ginsenosides. Current research is focused on efficiently and selectively removing sugar groups attached to the major ginsenoside sugar chains to convert them into rare ginsenosides that meet the demands of medical industry and functional foods. The methods for preparing rare ginsenosides encompass chemical, microbial, and enzymatic approaches. Among these, the enzyme conversion method is highly favored by researchers due to its exceptional specificity and robust efficiency. This review summarizes the biological activities of different rare ginsenosides, explores the various glycosidases used in the biotransformation of different major ginsenosides as substrates, and elucidates their respective corresponding biotransformation pathways. These findings will provide valuable references for the development, utilization, and industrial production of ginsenosides.

Engineered β-glycosidase from Hyperthermophilic Sulfolobus solfataricus with Improved Rd-hydrolyzing Activity for Ginsenoside Compound K Production

Hyperthermophilic Sulfolobus solfataricus β-glycosidase (SS-βGly), with higher stability and activity than mesophilic enzymes, has potential for industrial ginsenosides biotransformation. However, its relatively low ginsenoside Rd-hydrolyzing activity limits the production of pharmaceutically active minor ginsenoside compound K (CK). In this study, first, we used molecular docking to predict the key enzyme residues that may hypothetically interact with ginsenoside Rd. Then, based on sequence alignment and alanine scanning mutagenesis approach, key variant sites were identified that might improve the enzyme catalytic efficiency. The enzyme catalytic efficiency (kcat/Km) and substrate affinity (Km) of the N264D variant enzyme for ginsenoside Rd increased by 60% and decreased by 17.9% compared with WT enzyme, respectively, which may be due to a decrease in the binding free energy (∆G) between the variant enzyme and substrate Rd. In addition, Markov state models (MSM) analysis during the whole 1000-ns MD simulations indicated that altering N264 to D made the variant enzyme achieve a more stable SS-βGly conformational state than the wild-type (WT) enzyme and corresponding Rd complex. Under identical conditions, the relative activities and the CK conversion rates of the N264D enzyme were 1.7 and 1.9 folds higher than those of the WT enzyme. This study identified an excellent hyperthermophilic β-glycosidase candidate for industrial biotransformation of ginsenosides.

Advances in the biosynthesis and metabolic engineering of rare ginsenosides

Rare ginsenosides are the deglycosylated secondary metabolic derivatives of major ginsenosides, and they are more readily absorbed into the bloodstream and function as active substances. The traditional preparation methods hindered the potential application of these effective components. The continuous elucidation of ginsenoside biosynthesis pathways has rendered the production of rare ginsenosides using synthetic biology techniques effective for their large-scale production. Previously, only the progress in the biosynthesis and biotechnological production of major ginsenosides was highlighted. In this review, we summarized the recent advances in the identification of key enzymes involved in the biosynthetic pathways of rare ginsenosides, especially the glycosyltransferases (GTs). Then the construction of microbial chassis for the production of rare ginsenosides, mainly in Saccharomyces cerevisiae, was presented. In the future, discovery of more GTs and improving their catalytic efficiencies are essential for the metabolic engineering of rare ginsenosides. This review will give more clues and be helpful for the characterization of the biosynthesis and metabolic engineering of rare ginsenosides. KEY POINTS: • The key enzymes involved in the biosynthetic pathways of rare ginsenosides are summarized. • The recent progress in metabolic engineering of rare ginsenosides is presented. • The discovery of glycosyltransferases is essential for the microbial production of rare ginsenosides in the future.

β-Glucosidase and Its Application in Bioconversion of Ginsenosides in Panax ginseng

Ginsenosides are a group of bioactive compounds isolated from Panax ginseng. Conventional major ginsenosides have a long history of use in traditional medicine for both illness prevention and therapy. Bioconversion processes have the potential to create new and valuable products in pharmaceutical and biological activities, making them both critical for research and highly economic to implement. This has led to an increase in the number of studies that use major ginsenosides as a precursor to generate minor ones using β-glucosidase. Minor ginsenosides may also have useful properties but are difficult to isolate from raw ginseng because of their scarcity. Bioconversion processes have the potential to create novel minor ginsenosides from the more abundant major ginsenoside precursors in a cost-effective manner. While numerous bioconversion techniques have been developed, an increasing number of studies have reported that β-glucosidase can effectively and specifically generate minor ginsenosides. This paper summarizes the probable bioconversion mechanisms of two protopanaxadiol (PPD) and protopanaxatriol (PPT) types. Other high-efficiency and high-value bioconversion processes using complete proteins isolated from bacterial biomass or recombinant enzymes are also discussed in this article. This paper also discusses the various conversion and analysis methods and their potential applications. Overall, this paper offers theoretical and technical foundations for future studies that will be both scientifically and economically significant.

Microorganisms for Ginsenosides Biosynthesis: Recent Progress, Challenges, and Perspectives

Ginsenosides are major bioactive compounds present in the Panax species. Ginsenosides exhibit various pharmaceutical properties, including anticancer, anti-inflammatory, antimetastatic, hypertension, and neurodegenerative disorder activities. Although several commercial products have been presented on the market, most of the current chemical processes have an unfriendly environment and a high cost of downstream processing. Compared to plant extraction, microbial production exhibits high efficiency, high selectivity, and saves time for the manufacturing of industrial products. To reach the full potential of the pharmaceutical resource of ginsenoside, a suitable microorganism has been developed as a novel approach. In this review, cell biological mechanisms in anticancer activities and the present state of research on the production of ginsenosides are summarized. Microbial hosts, including native endophytes and engineered microbes, have been used as novel and promising approaches. Furthermore, the present challenges and perspectives of using microbial hosts to produce ginsenosides have been discussed.

Biotransformation of Platycosides, Saponins from Balloon Flower Root, into Bioactive Deglycosylated Platycosides

Platycosides, saponins from balloon flower root (Platycodi radix), have diverse health benefits, such as antioxidant, anti-inflammatory, anti-tussive, anti-cancer, anti-obesity, anti-diabetes, and whitening activities. Deglycosylated platycosides, which show greater biological effects than glycosylated platycosides, are produced by the hydrolysis of glycoside moieties in glycosylated platycosides. In this review, platycosides are classified according to the chemical structures of the aglycone sapogenins and also divided into natural platycosides, including major, minor, and rare platycosides, depending on the content in Platycodi radix extract and biotransformed platycosides. The biological activities of platycosides are summarized and methods for deglycosylation of saponins, including physical, chemical, and biological methods, are introduced. The biotransformation of glycosylated platycosides into deglycosylated platycosides was described based on the hydrolytic pathways of glycosides, substrate specificity of glycosidases, and specific productivities of deglycosylated platycosides. Methods for producing diverse and/or new deglycosylated platycosides are also proposed.

High-Value Bioconversion of Ginseng Extracts in Betaine-Based Deep Eutectic Solvents for the Preparation of Deglycosylated Ginsenosides

Deep eutectic solvents (DES), as a green alternative to traditional organic solvents in biocatalysis, not only activate proteins but even increase the efficiency of enzymatic reactions. Here, DES were used in a combinatorial enzyme-catalyzed system containing β-glucosidase BGLAt and β-galactosidase BGALAo to produce deglycosylated ginsenosides (De-g) from ginseng extracts (GE). The results showed that DES prepared with betaine and ethylene glycol (molar ratio, 1:2) could significantly stimulate the activity of the combinatorial enzymes as well as improve the acid resistance and temperature stability. The DES-based combinatorial enzyme-catalyzed system could convert 5 g of GE into 1.24 g of De-g (F1, F2, 20 (S)-PPT, and CK) at 24 h, which was 1.1 times that of the buffer sample. As confirmed by the spectral data, the changes in the conformations of the combinatorial enzymes were more favorable for the binding reaction with the substrates. Moreover, the constructed DES-based aqueous two-phase system enabled the recovery of substantial amounts of DES and De-g from the top phase. These results demonstrated that DES shows great application as a reaction solvent for the scale-up production of De-g and provide insights for the green extraction of natural products.

Progress in the Conversion of Ginsenoside Rb1 into Minor Ginsenosides Using β-Glucosidases

In recent years, minor ginsenosides have received increasing attention due to their outstanding biological activities, yet they are of extremely low content in wild ginseng. Ginsenoside Rb1, which accounts for 20% of the total ginsenosides, is commonly used as a precursor to produce minor ginsenosides via β-glucosidases. To date, many research groups have used different approaches to obtain β-glucosidases that can hydrolyze ginsenoside Rb1. This paper provides a compilation and analysis of relevant literature published mainly in the last decade, focusing on enzymatic hydrolysis pathways, enzymatic characteristics and molecular mechanisms of ginsenoside Rb1 hydrolysis by β-glucosidases. Based on this, it can be concluded that: (1) The β-glucosidases that convert ginsenoside Rb1 are mainly derived from bacteria and fungi and are classified as glycoside hydrolase (GH) families 1 and 3, which hydrolyze ginsenoside Rb1 mainly through the six pathways. (2) Almost all of these β-glucosidases are acidic and neutral enzymes with molecular masses ranging from 44-230 kDa. Furthermore, the different enzymes vary widely in terms of their optimal temperature, degradation products and kinetics. (3) In contrast to the GH1 β-glucosidases, the GH3 β-glucosidases that convert Rb1 show close sequence-function relationships. Mutations affecting the substrate binding site might alter the catalytic efficiency of enzymes and yield different prosapogenins. Further studies should focus on elucidating molecular mechanisms and improving overall performances of β-glucosidases for better application in food and pharmaceutical industries.

Enzymatic biotransformation of Rb3 from the leaves of Panax notoginseng to ginsenoside rd by a recombinant β-xylosidase from Thermoascus aurantiacus

Given the important pharmacological activity of ginsenoside Rd but its low content in plants, the production of Rd by enzymatic transformation is of interest. In this study, a β-xylosidase gene Ta-XylQS from Thermoascus aurantiacus was cloned and overexpressed in Komagataella phaffii. Purified recombinant Ta-XylQS specifically hydrolyzes substrates with xylosyl residues at the optimal pH of 3.5 and temperature of 60 °C. This study established a process for producing Rd by transforming ginsenoside Rb3 in the saponins of Panax notoginseng leaves via recombinant Ta-XylQS. After 60 h, 3 g L^- 1 of Rb3 was transformed into 1.46 g L^- 1 of Rd, and the maximum yield of Rd reached 4.31 g kg^- 1 of Panax notoginseng leaves. This study is the first report of the biotransformation of ginsenoside Rb3 to Rd via a β-xylosidase, and the established process could potentially be adopted for the commercial production of Rd from Rb3.

Production of Minor Ginsenosides from Panax notoginseng Flowers by Cladosporium xylophilum

Panax notoginseng flowers have the highest content of saponins compared to the other parts of Panax notoginseng, but minor ginsenosides have higher pharmacological activity than the main natural ginsenosides. Therefore, this study focused on the transformation of the main ginsenosides in Panax notoginseng flowers to minor ginsenosides using the fungus of Cladosporium xylophilum isolated from soil. The main ginsenosides Rb₁, Rb₂, Rb₃, and Rc and the notoginsenoside Fa in Panax notoginseng flowers were transformed into the ginsenosides F₂ and Rd₂, the notoginsenosides Fd and Fe, and the ginsenoside R₇; the conversion rates were 100, 100, 100, 88.5, and 100%, respectively. The transformation products were studied by TLC, HPLC, and MS analyses, and the biotransformation pathways of the major ginsenosides were proposed. In addition, the purified enzyme of the fungus was prepared with the molecular weight of 66.4 kDa. The transformation of the monomer ginsenosides by the crude enzyme is consistent with that by the fungus. Additionally, three saponins were isolated from the transformation products and identified as the ginsenoside Rd₂ and the notoginsenosides Fe and Fd by NMR and MS analyses. This study provided a unique and powerful microbial strain for efficiently transformating major ginsenosides in P. notoginseng flowers to minor ginsenosides, which will help raise the functional and economic value of the P. notoginseng flower.

Production of Minor Ginsenoside CK from Major Ginsenosides by Biotransformation and Its Advances in Targeted Delivery to Tumor Tissues Using Nanoformulations

For over 2000 years, ginseng (roots of Panax ginseng C.A. Meyer) has been used as a traditional herbal medicine. Ginsenosides are bioactive compounds present in ginseng responsible for the pharmacological effects and curing various acute diseases as well as chronic diseases including cardiovascular disease, cancer and diabetes. Structurally, ginsenosides consist of a hydrophobic aglycone moiety fused with one to four hydrophilic glycoside moieties. Based on the position of sugar units and their abundance, ginsenosides are classified into major and minor ginsenosides. Despite the great potential of ginsenosides, major ginsenosides are poorly absorbed in the blood circulation, resulting in poor bioavailability. Interestingly, owing to their small molecular weight, minor ginsenosides exhibit good permeability across cell membranes and bioavailability. However, extremely small quantities of minor ginsenosides extracted from ginseng plants cannot fulfill the requirement of scientific and clinical studies. Therefore, the production of minor ginsenosides in mass production is a topic of interest. In addition, their poor solubility and lack of targetability to tumor tissues limits their application in cancer therapy. In this review, various methods used for the transformation of major ginsenosides to minor ginsenoside compound K (CK) are summarized. For the production of CK, various transformation methods apply to major ginsenosides. The challenges present in these transformations and future research directions for producing bulk quantities of minor ginsenosides are discussed. Furthermore, attention is also paid to the utilization of nanoformulation technology to improve the bioavailability of minor ginsenoside CK.

Increased Production of Ginsenoside Compound K by Optimizing the Feeding of American Ginseng Extract during Fermentation by Aspergillus tubingensis

The ginsenoside compound K (C-K) is widely used in traditional medicines, nutritional supplements, and cosmetics owing to its diverse pharmacological activities. Although many studies on C-K production have been conducted, fermentation is reported to produce C-K with low concentration and productivity. In the present study, addition of an inducer and optimization of the carbon and nitrogen sources in the medium were performed using response surface methodology to increase the C-K production via fermentation by Aspergillus tubingensis, a generally recognized as safe fungus. The optimized inducer and carbon and nitrogen sources were 2 g/l rice straw, 10 g/l sucrose, and 10 g/l soy protein concentrate, respectively, and they resulted in a 3.1-fold increase in the concentration and productivity of C-K (0.22 g/l and 1.52 mg/l/h, respectively) compared to those used before optimization without inducer (0.071 g/l and 0.49 mg/l/h, respectively). The feeding methods of American ginseng extract (AGE), including feeding timing, feeding concentration, and feeding frequency, were also optimized. Under the optimized conditions, A. tubingensis produced 3.96 mM (2.47 g/l) C-K at 144 h by feeding two times with 8 g/l AGE at 48 and 60 h, with a productivity of 17.1 mg/l/h. The concentration and productivity of C-K after optimization of feeding methods were 11-fold higher than those before the optimization (0.22 g/l and 1.52 mg/l/h, respectively). Thus, the optimization for the feeding methods of ginseng extract is an efficient strategy to increase C-K production. To our knowledge, this is the highest reported C-K concentration and productivity via fermentation reported so far.

Novel β-Glucosidase Mibgl3 from Microbacterium sp. XT11 with Oligoxanthan-Hydrolyzing Activity

The enzymatic pathway of xanthan depolymerization has been predicted previously; however, the β-glucosidase and unsaturated glucuronyl hydrolase in this system have not been cloned and characterized. This lack of knowledge hinders rational modification of xanthan and exploration of new applications. In this work, we report on the properties of Mibgl3, a xanthan-degrading enzyme isolated from Microbacterium sp. XT11. Mibgl3 exhibits typical structural features of the GH3 family but shares low sequence identity with reported GH3 enzymes. The activity of Mibgl3 can be inhibited by Cu²⁺, Fe²⁺, Zn²⁺, and glucose. Unlike most β-glucosidases, Mibgl3 can tolerate a wide pH range and is activated by high concentrations of NaCl. This improves the commercial value of Mibgl3. In particular, Mibgl3 exhibits higher substrate specificity toward oligoxanthan than other β-glucosidases. Ion chromatography, ultrahigh-performance liquid chromatography-mass spectrometry (UPLC-MS), and GC-MS results showed that Mibgl3 could effectively hydrolyze oligoxanthan to release glucose and glucuronate. Therefore, Mibgl3 might play an important role in xanthan depolymerization by functioning as hydrolase of both the xanthan backbone and sidechains. This knowledge of the enzymatic properties and hydrolysis mechanism of a β-glucosidase will be beneficial for future applications.

Advances and challenges in ginseng research from 2011 to 2020: the phytochemistry, quality control, metabolism, and biosynthesis

Covering: 2011 to the end of 2020Panax species (Araliaceae), particularly P. ginseng, P. quinquefolius, and P. notoginseng, have a long history of medicinal use because of their remarkable tonifying effects, and currently serve as crucial sources for various healthcare products, functional foods, and cosmetics, aside from their vast clinical preparations. The huge market demand on a global scale prompts the continuous prosperity in ginseng research concerning the discovery of new compounds, precise quality control, ADME (absorption/disposition/metabolism/excretion), and biosynthesis pathways. Benefitting from the ongoing rapid development of analytical technologies, e.g. multi-dimensional chromatography (MDC), personalized mass spectrometry (MS) scan strategies, and multi-omics, highly recognized progress has been made in driving ginseng analysis towards "systematicness, integrity, personalization, and intelligentization". Herein, we review the advances in the phytochemistry, quality control, metabolism, and biosynthesis pathway of ginseng over the past decade (2011-2020), with 410 citations. Emphasis is placed on the introduction of new compounds isolated (saponins and polysaccharides), and the emerging novel analytical technologies and analytical strategies that favor ginseng's authentic use and global consumption. Perspectives on the challenges and future trends in ginseng analysis are also presented.

Enhanced biotransformation of the minor ginsenosides in red ginseng extract by Penicillium decumbens β-glucosidase

Compound K (C-K) and Rh2, which are present at low levels in ginseng and ginseng extracts, have higher intestinal absorption rates than other ginsenosides. Here, we attempted to convert ginsenoside Rb1 to C-K using a β-glucosidase from Penicillium decumbens. Ten commercially available enzymes were screened to identify enzymes that can convert ginsenoside Rb1 to C-K, resulting in the selection of a P. decumbens-derived β-glucosidase. β-Glucosidase showed maximum activity at pH 4.0 and 60 °C; its substrate specificity for ginsenoside Rb1 was investigated. The main glucoside-hydrolyzing pathways were as follows: ginsenoside Rb1 or Rd → gypenoside XVII → F2 → C-K and ginsenoside Rg3 → Rh2. The P. decumbens-derived β-glucosidase was used to generate C-K and Rh2 using protopanaxadiol-type ginsenosides as substrates. Additionally, to apply this enzyme to the commercialized red ginseng extract products, the contents of C-K and Rh2 in the total ginsenosides significantly (p < 0.05) increased up to 36-fold and 8.9-fold, respectively, higher than prior to subjecting to biotransformation. To the best of our knowledge, this is the first report of the dual biotransformation of C-K and Rh2 by a food-grade commercial enzyme. This study demonstrates that the use of a specific β-glucosidase may increase C-K and Rh2 contents in the ginseng extract through a simple biotransformation process and, thus, enhance its health benefits.

Improved production of deglucosylated platycodin D from saponins from balloon flower leaf by a food-grade enzyme using high hydrostatic pressure

Platycosides, saponins contained in balloon flower, which have been used as food health supplements for respiratory diseases, have diverse pharmacological effects. Platycosides exhibit better pharmacological activity by hydrolyzing their own sugars. However, to date, there have been no studies on the production of deglucosylated platycodin D suitable for food applications. In this study, Pluszyme 2000P, which was derived from Aspergillus niger, a food-grade microorganism, was used to completely convert platycoside E into deglucosylated platycodin D. For an efficient and economical production of deglucosylated platycodin D, the productivity was improved approximately 2.4 times by application of high hydrostatic pressure and the discarded balloon flower leaf was used as a substrate. As a result, deglucosylated platycodin D was produced with the highest concentration (3.49 mg/mL) and productivity (581.7 mg/L/h) reported so far. Our results contribute to functional saponin production and the related food industries.

Qualitatively and quantitatively investigating the metabolism of 20(S)-protopanaxadiol-type ginsenosides by gut microbiota of different species

Ginsenosides Rb1, Rb2, Rb3 and Rc, four major protopanaxadiol (PPD)-type ginsenosides, can be metabolized by gut microbiota. The composition of gut microbiota varies in different species. Existing publications have reported the metabolite fates of ginsenosides by gut microbiota from single species. However, their microbiota-related metabolic species differences have not been evaluated yet. In current study, in vitro anaerobic incubations of PPD-type ginsenosides with gut microbiota from humans, rabbits and rats were conducted. The metabolites of each ginsenoside were then identified by LC-MS. A total of 15 metabolites from the four ginsenosides were identified. The major metabolic pathways were stepwise removals of the C-20 and C-3 sugar moieties to obtain aglycone PPD. The results showed that the hydrolysis rate of C-20 terminal β-D-glucopyranosyl was significantly higher than those of α-L-arabinopyranosyl, β-D-xylopyranosyl and α-L-arabinofuranosyl in different species. The activity of β-glucosidase, the metabolic rates of parent compounds and the formation rates of their metabolites were significantly higher in gut microbiota from rabbits than from humans and rats. Our research draws researchers' attention to the species differences of microbiota-related drug metabolism.

Endophytes, biotransforming microorganisms, and engineering microbial factories for triterpenoid saponins production

Triterpenoid saponins are structurally diverse secondary metabolites. They are the main active ingredient of many medicinal plants and have a wide range of pharmacological effects. Traditional production of triterpenoid saponins, directly extracted from cultivated plants, cannot meet the rapidly growing demand of pharmaceutical industry. Microorganisms with triterpenoid saponins production ability (especially Agrobacterium genus) and biotransformation ability, such as fungal species in Armillaria and Aspergillus genera and bacterial species in Bacillus and Intestinal microflora, represent a valuable source of active metabolites. With the development of synthetic biology, engineering microorganisms acquired more potential in terms of triterpenoid saponins production. This review focusses on potential mechanisms and the high yield strategies of microorganisms with inherent production or biotransformation ability of triterpenoid saponins. Advances in the engineering of microorganisms, such as Saccharomyces cerevisiae, Yarrowia lipolytica, and Escherichia coli, for the biosynthesis triterpenoid saponins de novo have also been reported. Strategies to increase the yield of triterpenoid saponins in engineering microorganisms are summarized following four aspects, that is, introduction of high efficient gene, optimization of enzyme activity, enhancement of metabolic flux to target compounds, and optimization of fermentation conditions. Furthermore, the challenges and future directions for improving the yield of triterpenoid saponins biosynthesis in engineering microorganisms are discussed.

Complete Bioconversion of Protopanaxadiol-Type Ginsenosides to Compound K by Extracellular Enzymes from the Isolated Strain Aspergillus tubingensis

A compound K-producing fungus was isolated from meju (fermented soybean brick) and identified as the generally recognized as safe (GRAS) strain Aspergillus tubingensis. The extracellular enzymes obtained after the cultivation of 6 days in the medium with 20 g/L citrus pectin as an inducer showed the highest compound K-producing activity among the inducers tested. Under the optimized conditions of 0.05 mM MgSO₄, 55 °C, pH 4.0, 13.4 mM protopanaxadiol (PPD)-type ginsenosides, and 11 mg/mL enzymes, the extracellular enzymes from A. tubingensis completely converted PPD-type ginsenosides in the ginseng extract to 13.4 mM (8.35 mg/mL) compound K after 20 h, with the highest concentration and productivity among the results reported so far. As far as we know, this is the first GRAS enzyme to completely convert all PPD-type ginsenosides to compound K.

Biotransformation of Protopanaxadiol-Type Ginsenosides in Korean Ginseng Extract into Food-Available Compound K by an Extracellular Enzyme from Aspergillus niger

Compound K (C-K) is one of the most pharmaceutically effective ginsenosides, but it is absent in natural ginseng. However, C-K can be obtained through the hydrolysis of protopanaxadiol-type ginsenosides (PPDGs) in natural ginseng. The aim of this study was to obtain the high concentration of food-available C-K using PPDGs in Korean ginseng extract by an extracellular enzyme from Aspergillus niger KACC 46495. A. niger was cultivated in the culture medium containing the inducer carboxymethyl cellulose (CMC) for 6 days. The extracellular enzyme extracted from A. niger was prepared from the culture broth by filtration, ammonium sulfate, and dialysis. The extracellular enzyme was used for C-K production using PPDGs. The glycoside-hydrolyzing pathways for converting PPDGs into C-K by the extracellular enzyme were Rb1 → Rd → F2 → C-K, Rb2 → Rd or compound O → F2 or compound Y → C-K, and Rc → Rd or compound Mc1 → F2 or compound Mc → C-K. The extracellular enzyme from A. niger at 8.0 mg/ml, which was obtained by the induction of CMC during the cultivation, converted 6.0 mg/ml (5.6 mM) PPDGs in Korean ginseng extract into 2.8 mg/ml (4.5 mM) food-available C-K in 9 h, with a productivity of 313 mg/l/h and a molar conversion of 80%. To the best of our knowledge, the productivity and concentration of C-K of the extracellular enzyme are the highest among those by crude enzymes from wild-type microorganisms.

Advances in the Production of Minor Ginsenosides Using Microorganisms and Their Enzymes

Abstract Minor ginsenodes are of great interest due to their diverse pharmacological activities such as their anti-cancer, anti-diabetic, neuroprotective, immunomodulator, and anti-inflammatory effects. The miniscule amount of minor ginsenosides in ginseng plants has driven the development of their mass production methods. Among the various production methods for minor ginsenosides, the utilization of microorganisms and their enzymes are considered as highly specific, safe, and environmentally friendly. In this review, various minor ginsenosides production strategies, namely utilizing microorganisms and recombinant microbial enzymes, for biotransforming major ginsenosides into minor ginsenoside, as well as constructing synthetic minor ginsenosides production pathways in yeast cell factories, are described and discussed. Furthermore, the present challenges and future research direction for producing minor ginsenosides using those approaches are discussed.

Biocatalytic synthesis of ginsenoside Rh2 using Arabidopsis thaliana glucosyltransferase-catalyzed coupled reactions

Ginsenoside Rh2, a rare protopanaxadiol (PPD)-type triterpene saponin isolated from Panax ginseng, exhibits notable anticancer and immune-system-enhancing activities. Glycosylation catalyzed by uridine diphosphate-dependent glucosyltransferase (UGT) is the final biosynthetic step of ginsenoside Rh2. In this study, UGT73C5 isolated from Arabidopsis thaliana was demonstrated to selectively transfer a glucosyl moiety to the C3 hydroxyl group of PPD to synthesize ginsenoside Rh2. UGT73C5 was coupled with sucrose synthase (SuSy) from A. thaliana to regenerate costly uridine diphosphate glucose (UDPG) from cheap sucrose and catalytic amounts of uridine diphosphate (UDP). The UGT73C5/SuSy ratio, temperature, pH, cofactor UDP, and PPD concentrations for UGT73C5-SuSy coupled reactions were optimized. Through the stepwise addition of PPD, the maximal ginsenoside Rh2 production was 3.2 mg mL^-1, which was the highest yield reported to date. These promising results provided an efficient and cost-effective approach to semisynthesize the highly valuable ginsenoside Rh2.

Enzymatic Biotransformation of Balloon Flower Root Saponins into Bioactive Platycodin D by Deglucosylation with Caldicellulosiruptor bescii β-Glucosidase

Platycodin D (PD), a major saponin (platycoside) in Platycodi radix (balloon flower root), has higher pharmacological activity than the other major platycosides; however, its content in the plant root is only approximately 10% (w/w) and the productivities of PD by several enzymes are still too low for industrial applications. To rapidly increase the total PD content, the β-glucosidase from Caldicellulosiruptor bescii was used for the deglucosylation of the PD precursors platycoside E (PE) and platycodin D3 (PD3) in the root extract into PD. Under the optimized reaction conditions, the enzyme completely converted the PD precursors into PD with the highest productivity reported so far, increasing the total PD content to 48% (w/w). In the biotransformation process, the platycosides in Platycodi radix were hydrolyzed by four pathways: deapiosylated (deapi)-PE → deapi-PD3 → deapi-PD, PE → PD3 → PD, polygalacin D3 → polygalacin D, and 3″-O-acetyl polygalacin D3 → 3″-O-acetyl polygalacin D.

Complete Biotransformation of Protopanaxadiol-Type Ginsenosides into 20-O-β-Glucopyranosyl-20(S)-protopanaxadiol by Permeabilized Recombinant Escherichia coli Cells Coexpressing β-Glucosidase and Chaperone Genes

The ginsenoside 20-O-β-glucopyranosyl-20(S)-protopanaxadiol or compound K is an essential ingredient in functional food, cosmetics, and traditional medicines. However, no study has reported the complete conversion of all protopanaxadiol (PPD)-type ginsenosides from ginseng extract into compound K using whole-cell conversion. To increase the production of compound K from ginseng extract using whole recombinant cells, the β-glucosidase enzyme from Caldicellulosiruptor bescii was coexpressed with a chaperone expression system (pGro7), and the cells expressing the coexpression system were permeabilized with ethylenediaminetetraacetic acid. The permeabilized cells carrying the chaperone coexpression system showed a 2.6-fold increase in productivity and yield as compared with nontreated cells, and completely converted all PPD-type ginsenosides from ginseng root extract into compound K with the highest productivity among the results reported so far. Our results will contribute to the industrial biological production of compound K.

Biotransformation of Food-Derived Saponins, Platycosides, into Deglucosylated Saponins Including Deglucosylated Platycodin D and Their Anti-Inflammatory Activities

The Platycodon grandiflorum root, Platycodi radix, a common vegetable, and its extract with glycosylated saponins, platycosides, have been used as food items and food health supplements for pulmonary diseases and respiratory disorders. Enzymes convert glycosylated saponins into deglycosylated saponins, which exhibit higher biological activity than glycosylated saponins. In this study, β-glucosidase from the hyperthermophilic bacterium Dictyoglomus turgidum converted platycosides in the Platycodi radix extract into deglucosylated platycosides. In addition, the enzyme completely converted platycoside E (PE), platycodin D₃ (PD₃), and platycodin D (PD) in Platycodi radix extract into deglucosylated platycodin D (deglu PD), which was first identified by nuclear magnetic resonance. The anti-inflammatory activities of deglu PD and deglucosylated Platycodi radix extract were higher than those of PE, PD₃, PD, Platycodi radix extract, and baicalein, an anti-inflammatory agent. Therefore, deglucosylated Platycodi radix extract is expected to be used as improved functional food supplements.