Characterization of β-xylosidase from Thermoanaerobacterium thermosaccharolyticum and its application to the production of ginsenosides Rg1 and Rh1 from notoginsenosides R1 and R2

Production and pharmaceutical research of minor saponins in Panax notoginseng (Sanqi): Current status and future prospects

Panax notoginseng (Burk.) F.H. Chen is a traditional medicinal herb known as Sanqi or Tianqi in Asia and is commonly used worldwide. It is one of the main raw ingredients of Yunnan Baiyao, Fu fang dan shen di wan, and San qi shang yao pian. It is also a source of cardiotonic pill used to treat cardiovascular diseases in China, Korea, and Russia. Approximately 270 Panax notoginseng saponins have been isolated and identified as the major active components. Although the absorption and bioavailability of saponins are predominantly dependent on the gastrointestinal biotransformation capacity of an individual, minor saponins are better absorbed into the bloodstream and act as active substances than major saponins. Notably, minor saponins are absent or are present in minimal quantities under natural conditions. In this review, we focus on the strategies for the enrichment and production of minor saponins in P. notoginseng using physical, chemical, enzyme catalytic, and microbial methods. Moreover, pharmacological studies on minor saponins derived from P. notoginseng over the last decade are discussed. This review serves as a meaningful resource and guide, offering scholarly references for delving deeper into the exploration of the minor saponins in P. notoginseng.

Critical Roles of Acidic Residues in Loop Regions of the Structural Surface for the Salt Tolerance of a GH39 β-d-Xylosidase

Xylan is the main component of hemicellulose. Complete hydrolysis of xylan requires synergistically acting xylanases, such as β-d-xylosidases. Salt-tolerant β-d-xylosidases have significant application benefits, but few reports have explored the critical amino acids affecting the salt tolerance of xylosidases. Herein, the site-directed mutation was used to demonstrate that negative electrostatic potentials generated by 19 acidic residues in the loop regions of the structural surface positively correlated with the improved salt tolerance of GH39 β-d-xylosidase JB13GH39P28. These mutants showed reduced negative potentials on structural surfaces as well as a 13-43% decrease in stability in 3.0-30.0% (w/v) NaCl. Six key residue sites, D201, D259, D297, D377, D395, and D474, were confirmed to influence both the stability and activity of GH39 β-d-xylosidase. The activity of the GH39 β-d-xylosidase was found promoting by SO42- and inhibiting by NO3-. Values of Km and Kcat/Km decreased aggravatedly in 30.0% (w/v) NaCl when mutation operated on residues E179 and D182 in the loop regions of the catalytic domain. Taken together, mutation on acidic residues in loop regions from catalytic and noncatalytic domains may cause the deformation of catalytic pocket and aggregation of protein particles then decrease the stability, binding affinity, and catalytic efficiency of the β-d-xylosidase.

Tomato root-associated Sphingobium harbors genes for catabolizing toxic steroidal glycoalkaloids

IMPORTANCE

Saponins are a group of plant specialized metabolites with various bioactive properties, both for human health and soil microorganisms. Our previous works demonstrated that Sphingobium is enriched in both soils treated with a steroid-type saponin, such as tomatine, and in the tomato rhizosphere. Despite the importance of saponins in plant-microbe interactions in the rhizosphere, the genes involved in the catabolism of saponins and their aglycones (sapogenins) remain largely unknown. Here we identified several enzymes that catalyzed the degradation of steroid-type saponins in a Sphingobium isolate from tomato roots, RC1. A comparative genomic analysis of Sphingobium revealed the limited distribution of genes for saponin degradation in our saponin-degrading isolates and several other isolates, suggesting the possible involvement of the saponin degradation pathway in the root colonization of Sphingobium spp. The genes that participate in the catabolism of sapogenins could be applied to the development of new industrially valuable sapogenin molecules.

Enhancing the inhibition of cell proliferation and induction of apoptosis in H22 hepatoma cells through biotransformation of notoginsenoside R1 by Lactiplantibacillus plantarum S165 into 20(S/R)-notoginsenoside R2

Notoginsenoside R2 is a crucial active saponin in Panax notoginseng (Burk.) F. H. Chen, but its natural content is relatively low. In this study, we investigated the biotransformation of notoginsenoside R1 to 20(S/R)-notoginsenoside R2 using Lactiplantibacillus plantarum S165, compared the inhibitory effects on cancer cell proliferation and conducted a mechanistic study. Notoginsenoside R1 was transformed using Lactiplantibacillus plantarum S165 at 37 °C for 21 days. The fermentation products were identified using a combination of HPLC, UPLC-MS/MS, and 13C-NMR methods. The inhibition effects of 20(S/R)-notoginsenoside R2 on H22 hepatoma cells were assessed by CCK-8 and TUNEL assays, and the underlying mechanism was investigated by Western blotting. Lactiplantibacillus plantarum S165 could effectively transform notoginsenoside R1 to 20(S/R)-notoginsenoside R2 with a conversion yield of 82.85%. Our results showed that 20(S/R)-notoginsenoside R2 inhibited H22 hepatoma cells proliferation and promoted apoptosis. The apoptosis of H22 hepatoma cells was promoted by 20(S/R)-notoginsenoside R2 through the blockade of the PI3K/AKT/mTOR signaling pathway. The biotransformation method used in this study resulted in the production of 20(S)-notoginsenoside R2 and 20(R)-notoginsenoside R2 from notoginsenoside R1, and the anti-tumor activity of the transformed substance markedly improved.

Structures, Biochemical Characteristics, and Functions of β-Xylosidases

The complete degradation of abundant xylan derived from plants requires the participation of β-xylosidases to produce the xylose which can be converted to xylitol, ethanol, and other valuable chemicals. Some phytochemicals can also be hydrolyzed by β-xylosidases into bioactive substances, such as ginsenosides, 10-deacetyltaxol, cycloastragenol, and anthocyanidins. On the contrary, some hydroxyl-containing substances such as alcohols, sugars, and phenols can be xylosylated by β-xylosidases into new chemicals such as alkyl xylosides, oligosaccharides, and xylosylated phenols. Thus, β-xylosidases shows great application prospects in food, brewing, and pharmaceutical industries. This review focuses on the molecular structures, biochemical properties, and bioactive substance transformation function of β-xylosidases derived from bacteria, fungi, actinomycetes, and metagenomes. The molecular mechanisms of β-xylosidases related to the properties and functions are also discussed. This review will serve as a reference for the engineering and application of β-xylosidases in food, brewing, 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.

Alicyclobacillus mali FL18 as a Novel Source of Glycosyl Hydrolases: Characterization of a New Thermophilic β-Xylosidase Tolerant to Monosaccharides

A thermo-acidophilic bacterium, Alicyclobacillus mali FL18, was isolated from a hot spring of Pisciarelli, near Naples, Italy; following genome analysis, a novel putative β-xylosidase, AmβXyl, belonging to the glycosyl hydrolase (GH) family 3 was identified. A synthetic gene was produced, cloned in pET-30a(+), and expressed in Escherichia coli BL21 (DE3) RIL. The purified recombinant protein, which showed a dimeric structure, had optimal catalytic activity at 80 °C and pH 5.6, exhibiting 60% of its activity after 2 h at 50 °C and displaying high stability (more than 80%) at pH 5.0-8.0 after 16 h. AmβXyl is mainly active on both para-nitrophenyl-β-D-xylopyranoside (K_M 0.52 mM, k_cat 1606 s^-1, and k_cat/K_M 3088.46 mM^-1·s^-1) and para-nitrophenyl-α-L-arabinofuranoside (K_M 10.56 mM, k_cat 2395.8 s^-1, and k_cat/K_M 226.87 mM^-1·s^-1). Thin-layer chromatography showed its ability to convert xylooligomers (xylobiose and xylotriose) into xylose, confirming that AmβXyl is a true β-xylosidase. Furthermore, no inhibitory effect on enzymatic activity by metal ions, detergents, or EDTA was observed except for 5 mM Cu²⁺. AmβXyl showed an excellent tolerance to organic solvents; in particular, the enzyme increased its activity at high concentrations (30%) of organic solvents such as ethanol, methanol, and DMSO. Lastly, the enzyme showed not only a good tolerance to inhibition by xylose, arabinose, and glucose, but was activated by 0.75 M xylose and up to 1.5 M by both arabinose and glucose. The high tolerance to organic solvents and monosaccharides together with other characteristics reported above suggests that AmβXyl may have several applications in many industrial fields.

Progress in research of glycoside hydrolases in the intestine

Glycoside hydrolases are a class of enzymes that hydrolyze glycosides and play an important role in the metabolic transformation of glycosides in the intestine, but the number of glycoside hydrolases encoded and expressed in the body is limited, and most glycoside hydrolases are produced from intestinal bacteria genes. Gut microbiota and the secreted glycoside hydrolases participate in the deglycosylation of glycosides and improve their bioavailability. In this paper, we review the definition and types of glucoside hydrolases, their sources from the gut microbiota, and transformation of glycosides by the gut microbiota. We also discuss the relationship between the gut microbiota, glucoside hydrolases, and glucoside deglycosylation transformation products, with an aim to provide a reference for efficient production of enzymes and glycoside conversion products, and mining of new drug resources.

Enzymatic hydrolysis of lignocellulosic biomass using a novel, thermotolerant recombinant xylosidase enzyme from Clostridium clariflavum: a potential addition for biofuel industry

The present study describes the cloning, expression, purification and characterization of the xylosidase gene (1650 bp) from a thermophilic bacterium Clostridium clariflavum into E. coli BL21 (DE3) using the expression vector pET-21a(+) for utilization in biofuel production. The recombinant xylosidase enzyme was purified to homogeneity by heat treatment and immobilized metal ion affinity chromatography. SDS-PAGE determined that the molecular weight of purified xylosidase was 60 kDa. This purified recombinant xylosidase showed its maximum activity at a temperature of 37 °C and pH 6.0. The purified recombinant xylosidase enzyme remains stable up to 90 °C for 4 h and retained 54.6% relative activity as compared to the control. The presence of metal ions such as Ca²⁺ and Mg²⁺ showed a positive impact on xylosidase enzyme activity whereas Cu²⁺ and Hg²⁺ inhibit its activity. Organic solvents did not considerably affect the stability of the purified xylosidase enzyme while DMSO and SDS cause the inhibition of enzyme activity. Pretreatment experiments were run in triplicate for 72 h at 30 °C using 10% NaOH. Saccharification experiment was performed by using 1% substrate (pretreated plant biomass) in citrate phosphate buffer of pH 6.5 loaded with 150 U mL⁻¹ of purified recombinant xylosidase enzyme along with ampicillin (10  μg mL⁻¹). Subsequent incubation was carried out at 50 °C and 100 rpm in a shaking incubator for 24 h. Saccharification potential of the recombinant xylosidase enzyme was calculated against both pretreated and untreated sugarcane bagasse and wheat straw as 9.63% and 8.91% respectively. All these characteristics of the recombinant thermotolerant xylosidase enzyme recommended it as a potential candidate for biofuel industry.

The present study describes the cloning, expression, purification and characterization of a xylosidase gene from Clostridium clariflavum into E. coli BL21 (DE3) using the expression vector pET-21a(+) for utilization in biofuel production.

Highly Efficient Biotransformation of Notoginsenoside R1 into Ginsenoside Rg1 by Dictyoglomus thermophilum β-xylosidase Xln-DT

Notoginsenoside R1 and ginsenoside Rg1 are the main active ingredients of Panax notoginseng, exhibiting anti-fatigue, anti-tumor, anti-inflammatory, and other activities. In a previous study, a GH39 β-xylosidase Xln-DT was responsible for the bioconversion of saponin, a natural active substance with a xylose group, with high selectivity for cleaving the outer xylose moiety of notoginsenoside R1 at the C-6 position, producing ginsenoside Rg1 with potent anti-fatigue activity. The optimal bioconversion temperature, pH, and enzyme dosage were obtained by optimizing the transformation conditions. Under optimal conditions (pH 6.0, 75°C, enzyme dosage 1.0 U/ml), 1.0 g/l of notoginsenoside R1 was converted into 0.86 g/l of ginsenoside Rg1 within 30 min, with a molar conversion rate of approximately 100%. Furthermore, the in vivo anti-fatigue activity of notoginsenoside R1 and ginsenoside Rg1 were compared using a suitable rat model. Compared with the control group, the forced swimming time to exhaustion was prolonged in mice by 17.3% in the Rg1 high group (20 mg/kg·d). Additionally, the levels of hepatic glycogen (69.9-83.3% increase) and muscle glycogen (36.9-93.6% increase) were increased. In the Rg1 group, hemoglobin levels were also distinctly increased by treatment concentrations. Our findings indicate that treatment with ginsenoside Rg1 enhances the anti-fatigue effects. In this study, we reveal a GH39 β-xylosidase displaying excellent hydrolytic activity to produce ginsenoside Rg1 in the pharmaceutical and food industries.

Cordyceps sinensis-mediated biotransformation of notoginsenoside R1 into 25-OH-20(S/R)-R2 with elevated cardioprotective effect against DOX-induced cell injury

Notoginsenoside R1 is a dammarane saponin in Panax notoginseng with promising cardioprotective effects. The bioactivity–structure relationship of such saponins suggested that the presence of a hydroxyl group at C25 could elevate its performance. To fulfill that goal, bioconversion of notoginsenoside R1 was mediated by a biocatalytic system of Cordyceps sinensis that had successfully produced multiple 25-OH derivatives from ginsenoside Re and Rg1. The major metabolic products of notoginsenoside R1 were identified as 25-OH-20(S/R)-R2 via the techniques of HRMS, ¹³C-NMR, ¹H-NMR, HSQC and HMBC. Time-course experiments were designed to monitor the reaction process, establishing a biocatalytic pathway of “R1→20(S/R)-R2→25-OH-20(S/R)-R2”. The bioconversion rate of these 25-OH derivatives added up to 69.87% which greatly precedes the previous report. Afterwards, the effect of these biocatalytic products against doxorubicin-induced cardiotoxicity was evaluated, indicating a significant increase in efficacy after the hydration of the C24–C25 double bond on the dammarane skeleton. In conclusion, the biocatalytic system employed in this paper is able to harvest 25-OH-20(S/R)-R2 in high yield from notoginsenoside R1, which will provide lead compounds or drug candidates to alleviate myocardial injury caused by doxorubicin.

The biocatalytic system in this paper preferably yielded 25-OH notoginsenoside R2 from R1 in a regioselective manner. Such a process significantly elevated the effects of these 25-OH derivatives against DOX-induced cardiomyocyte injury.

High-level expression of a novel multifunctional GH3 family β-xylosidase/α-arabinosidase/β-glucosidase from Dictyoglomus turgidum in Escherichia coli

A novel β-xylosidase Dt-2286 from Dictyoglomus turgidum was cloned and overexpressed in Escherichia coli BL21 (DE3). Dt-2286 belonging to glycoside hydrolase (GH) family 3 encodes a polypeptide with 762 amino acid residues with a molecular weight of 85.1 kDa. By optimization of the growth and induction conditions, the activity of β-xylosidase reached 273 U/mL, which is the highest yield reported to date from E. coli in a shake-flask. The optimal activities of the purified Dt-2286 were found at pH 5.0 and 98 °C. It also shows excellent thermostable/haloduric/organic solvent-tolerance. Dt-2286 was revealed to be a multifunctional enzyme with β-xylosidase, α-arabinofuranoside, α-arabinopyranoside and β-glucosidase activities, and K_cat/K_m was 5245.316 mM^-1 s^-1, 2077.353 mM^-1 s^-1, 1626.454 mM^-1 s^-1, and 470.432 mM^-1 s^-1 respectively. Dt-2286 showed significant synergistic effects on the degradation of xylans, releasing more reduced sugars (up to 15.08 fold) by simultaneous addition with endoxylanase. Moreover, this enzyme has good activity in the hydrolysis of epimedium B, demonstrating its versatility in practical applications.

Crystal structure of Dictyoglomus thermophilum β-d-xylosidase DtXyl unravels the structural determinants for efficient notoginsenoside R1 hydrolysis

Dictyoglomus thermophilum β-d-xylosidase DtXyl is attractive as a potential thermostable biocatalyst able to produce biologically active ginsenosides intermediates from β-(1,2)-D-xylosylated compounds, including Notoginsenoside-R1. DtXyl was expressed as an active N-terminal His-tagged protein, and its crystal structure was solved in presence or absence of d-xylose product. Modelling of notoginsenoside R1 in DtXyl active site led to the identification of several hydrophobic residues interacting in close contact to the substrate hydrophobic core. Unlike other residues involved in substrate binding, these residues are not conserved among GH39 xylosidase family, and their physico-chemical properties can be correlated to the efficient binding and subsequent hydrolysis of Notoginsenoside R1.

Cloning and characterization of the β-xylosidase from Dictyoglomus turgidum for high efficient biotransformation of 10-deacetyl-7-xylosltaxol

With the aim of finding an extracellular biocatalyst that can efficiently remove the C-7 xylose group from 10-deacetyl-7-xylosltaxol, a Dictyoglomus turgidum β-xylosidase was cloned and expressed in Escherichia coli BL21 (DE3). The molecular mass of purified Dt-Xyl3 was approximately 84 kDa. The recombinant Dt-Xyl3 was most active at pH 5.0 and 75 °C, retaining 88% activity at 65 °C for 1 h, and displaying excellent stability over pH 4.0-7.5 for 24 h. In terms of kinetic parameters, the K_m and V_max values for pNPX were 0.8316 mM and 5.0178 μmol/mL·min, respectively. Moreover, Dt-Xyl3 was activated by Mn²⁺ and Ba²⁺ and inhibited by Cu²⁺, Ni⁺ and Al³⁺. In particular, it displayed high tolerance to salts with 60.8% activity in 20% (w/v) NaCl. Ethanol and methanol at 5-15% showed little effect on the enzymatic activity. Dt-Xyl3 demonstrated multifunctional activities followed by pNPX, pNPAraf and pNPG and had a high selectivity for cleaving the outer xylose moieties of 10-deacetyl-7-xylosltaxol with K_cat/K_m 110.87 s^-1/mM, which produced 10-deacetyl-taxol to semi-synthesize paclitaxel. Under the optimized conditions (60 °C, pH 4.5, enzyme dosage of 0.5 U/mL), 1 g of 10-deacetyl-7-xylosltaxol was transformed to its corresponding aglycone 10-deacetyl-taxol within 30 min, with a molar conversion of 98%. This is the first report that Dictyoglomus turgidum can produce extracellular GH3 β-xylosidase with highly specific activity for 10-deacetyl-7-xylosltaxol biotransformation, thus leading to the application of β-xylosidase Dt-Xyl3 as a biocatalyst in biopharmaceutics.

Glycoside Hydrolase Family 39 β-Xylosidases Exhibit β-1,2-Xylosidase Activity for Transformation of Notoginsenosides: A New EC Subsubclass

β-1,2-Xylosidase activity has not been recorded as an EC subsubclass. In this study, phylogenetic analysis and multiple sequence alignments revealed that characterized β-xylosidases of glycoside hydrolase family (GH) 39 were classified into the same subgroup with conserved amino acid residue positions participating in substrate recognition. Protein-ligand docking revealed that seven of these positions were probably essential to bind xylose-glucose, which is linked by a β-1,2-glycosidic bond. Amino acid residues in five of the seven positions are invariant, while those in two of the seven positions are variable with low frequency. Both the wild-type β-xylosidase rJB13GH39 and its mutants with mutation at the two positions exhibited β-1,2-xylosidase activity, as they hydrolyzed o-nitrophenyl-β-d-xylopyranoside and transformed notoginsenosides R₁ and R₂ to ginsenosides Rg₁ and Rh₁, respectively. The results suggest that all of these characterized GH 39 β-xylosidases probably show β-1,2-xylosidase activity, which should be assigned an EC number with these β-xylosidases as representatives.

Glycoside Hydrolase Family 39 β-Xylosidase of Sphingomonas Showing Salt/Ethanol/Trypsin Tolerance, Low-pH/Low-Temperature Activity, and Transxylosylation Activity

Mining for novel enzymes from new microorganisms is a way to obtain β-xylosidases with promising applications. A Sphingomonas β-xylosidase was expressed in Escherichia coli. The purified recombinant enzyme (rJB13GH39) was most active at pH 4.5 and 50 °C, retaining 10%-50% of its maximum activity at 0-20 °C. Most salts and chemical reagents including 3.0%-20.0% (w/v) NaCl showed little or no effect on the enzymatic activity. rJB13GH39 exhibited 71.9% and 55.2% activity in 10.0% and 15.0% (v/v) ethanol, respectively. rJB13GH39 was stable below 60 °C in 3.0%-30.0% (w/v) NaCl, 3.0%-20.0% (v/v) ethanol, and 2.2-87.0 mg/mL trypsin. The enzyme transferred one xylosyl moiety to certain sugars and alcohols. The salt/ethanol tolerance and low-temperature activity of the enzyme may be attributed to its high structural flexibility caused by high proportions of small amino acids ACDGNSTV and random coils.

Characterization of a novel thermostable and xylose-tolerant GH 39 β-xylosidase from Dictyoglomus thermophilum

Background

β-D-xylosidase is a vital exoglycosidase with the ability to hydrolyze xylooligosaccharides to xylose and to biotransform some saponins by cleaving outer β-xylose. β-D-xylosidase is widely used as one of the xylanolytic enzymes in a diverse range of applications, such as fuel, food and the pharmaceutical industry; therefore, more and more studies have focused on the thermostable and xylose-tolerant β-D-xylosidases.

Results

A thermostable β-xylosidase gene (xln-DT) of 1509 bp was cloned from Dictyoglomus thermophilum and expressed in E.coli BL21. According to the amino acid and phylogeny analyses, the β-xylosidase Xln-DT is a novel β-xylosidase of the GH family 39. The recombinant β-xylosidase was purified, showing unique bands on SDS-PAGE, and had a protein molecular weight of 58.7 kDa. The β-xylosidase Xln-DT showed an optimal activity at pH 6.0 and 75 °C, with p-nitrophenyl-β-D-xylopyranoside (pNPX) as a substrate. Xln-DT displayed stability over a pH range of 4.0-7.5 for 24 h and displayed thermotolerance below 85 °C. The values of the kinetic parameters K_m and V_max for pNPX were 1.66 mM and 78.46 U/mg, respectively. In particular, Xln-DT displayed high tolerance to xylose, with 60% activity in the presence of 3 M xylose. Xln-DT showed significant effects on the hydrolyzation of xylobiose. After 3 h, all the xylobiose tested was degraded into xylose. Moreover, β-xylosidase Xln-DT had a high selectivity for cleaving the outer xylose moieties of natural saponins, such as notoginsenoside R1 and astragaloside IV, which produced the ginsenoside Rg1 with stronger anti-fatigue activity and produced cycloastragenol with stronger anti-aging activity, respectively.

Conclusion

This study provides a novel GH 39 β-xylosidase displaying extraordinary properties of highly catalytic activity at temperatures above 75 °C, remarkable hydrolyzing activity of xylooligosaccharides and rare saponins producing ability in the pharmaceutical and commercial industries.

Electronic supplementary material

The online version of this article (10.1186/s12896-018-0440-3) contains supplementary material, which is available to authorized users.

A literature update elucidating production of Panax ginsenosides with a special focus on strategies enriching the anti-neoplastic minor ginsenosides in ginseng preparations

Ginseng, an oriental gift to the world of healthcare and preventive medicine, is among the top ten medicinal herbs globally. The constitutive triterpene saponins, ginsenosides, or panaxosides are attributed to ginseng's miraculous efficacy towards anti-aging, rejuvenating, and immune-potentiating benefits. The major ginsenosides such as Rb1, Rb2, Rc, Rd., Re, and Rg1, formed after extensive glycosylations of the aglycone "dammaranediol," dominate the chemical profile of this genus in vivo and in vitro. Elicitations have successfully led to appreciable enhancements in the production of these major ginsenosides. However, current research on ginseng biotechnology has been focusing on the enrichment or production of the minor ginsenosides (the less glycosylated precursors of the major ginsenosides) in ginseng preparations, which are either absent or are produced in very low amounts in nature or via cell cultures. The minor ginsenosides under current scientific scrutiny include diol ginsenosides such as Rg3, Rh2, compound K, and triol ginsenosides Rg2 and Rh1, which are being touted as the next "anti-neoplastic pharmacophores," with better bioavailability and potency as compared to the major ginsenosides. This review aims at describing the strategies for ginsenoside production with special attention towards production of the minor ginsenosides from the major ginsenosides via microbial biotransformation, elicitations, and from heterologous expression systems.

Classification of glycosidases that hydrolyze the specific positions and types of sugar moieties in ginsenosides

Ginsenosides are the main compounds with pharmacological activities in ginseng. Deglycosylated ginsenosides, which are more pharmacologically active than glycosylated ginsenosides, can be produced by the specific or nonspecific hydrolysis of the sugar moieties in glycosylated ginsenosides using glycosidases. The enzymes that hydrolyze specifically ginsenosides with different types can be classified according to the enzymatic activity on the positions, inner and outer residues and types of sugar moieties in ginsenosides. Glycosylated ginsenosides are also hydrolyzed to deglycosylated ginsenosides with different hydrolytic pathways by cell conversion or fermentation. The biochemical properties of glycosidases involved in ginsenoside hydrolysis - ginsenosidases - were newly arranged and reviewed in accordance with different types. The combination of different-type ginsenosidases is suggested herein as an efficient tool to produce industrially important ginsenosides.