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1.
JG Hou JJ Xue MQ Sun CY Wang L Liu DL Zhang MR Lee LJ Gu CL Wang YB Wang Y Zheng W Li CK Sung 《Journal of applied microbiology》2012,113(4):807-814
Aims
This study examined the biotransformation pathway of ginsenoside Rb1 by the fungus Esteya vermicola CNU 120806.Methods and Results
Ginsenosides Rb1 and Rd were extracted from the root of Panax ginseng. Liquid fermentation and purified enzyme hydrolysis were employed to investigate the biotransformation of ginsenoside Rb1. The metabolites were identified and confirmed using NMR analysis as gypenoside XVII and gypenoside LXXV. A mole yield of 95·4% gypenoside LXXV was obtained by enzymatic conversion (pH 5·0, temperature 50°C). Ginsenoside Rd was used to verify the transformation pathway under the same reaction condition. The product Compound K (mole yield 49·6%) proved a consecutive hydrolyses occurred at the C‐3 position of ginsenoside Rb1.Conclusions
Strain CNU 120806 showed a high degree of specific β‐glucosidase activity to convert ginsenosides Rb1 and Rd to gypenoside LXXV and Compound K, respectively. The maximal activity of the purified glucosidase for ginsenosides transformation occurred at 50°C and pH 5·0. Compared with its activity against pNPG (100%), the β‐glucosidase exhibited quite lower level of activity against other aryl‐glycosides. Enzymatic hydrolysate, gypenoside LXXV and Compound K were produced by consecutive hydrolyses of the terminal and inner glucopyranosyl moieties at the C‐3 carbon of ginsenoside Rb1 and Rd, giving the pathway: ginsenoside Rb1→ gypenoside XVII → gypenoside LXXV; ginsenoside Rd→F2→Compound K, but did not hydrolyse the 20‐C, β‐(1‐6)‐glucoside of ginsenoside Rb1 and Rd.Significance and Impact of the Study
The results showed an important practical application on the preparation of gypenoside LXXV. Additionally, this study for the first time provided a high efficient preparation method for gypenoside LXXV without further conversion, which also gives rise to a potential commercial enzyme application. 相似文献2.
Chun Yan Wang Zhe Ming Fang Zhen Wang Dong Liang Zhang Li Juan Gu Mi Ra Lee Lei Liu Chang Keun Sung 《BioControl》2011,56(1):91-100
Esteya vermicola (Ophiostomataceae) is the first reported endoparasitic fungus of the pinewood nematode (PWN), Bursaphelenchus xylophilus (Nematoda: Aphelenchoidoidea). It has high in vitro infectivity. In this study, the nematocidal effect of E. vermicola in logs was investigated and evaluated. Two months after inoculation of pine wilt-killed Pinus densiflora logs with E. vermicola conidia suspensions of 3 × 108 and 3 × 106 ml−1, the density of nematodes decreased by approximately 79% and 47%, respectively. When the fungus was sprayed on to four-year-old
pine seedlings one month before PWN inoculation, the survival index of seedlings reached 0.67 compared with only 0.067 for
control seedlings without fungal spraying. These results suggest that conidia spraying of E. vermicola can, to some extent, protect pine trees from wilt disease. Moreover, infected nematodes and hyphae of E. vermicola were observed in the treated wood sections. 相似文献
3.
Xuesong Zhao Juan Wang Jie Li Ling Fu Juan Gao Xiuli Du Hongtao Bi Yifa Zhou Guihua Tai 《Journal of industrial microbiology & biotechnology》2009,36(5):721-726
Fourteen phytopathogenic fungi were tested for their ability to transform the major ginsenosides to the active minor ginsenoside
Rd. The transformation products were identified by TLC and HPLC, and their structures were assigned by NMR analysis. Cladosporium fulvum, a tomato pathogen, was found to transform major ginsenoside Rb1 to Rd as the sole product. The following optimum conditions for transforming Rd by C. fulvum were determined: the time of substrate addition, 24 h; substrate concentration, 0.25 mg ml−1; temperature, 37°C; pH 5.0; and biotransformation period, 8 days. At these optimum conditions, the maximum yield was 86%
(molar ratio). Further, a preparative scale transformation with C. fulvum was performed at a dose of 100 mg of Rb1 by a yield of 80%. This fungus has potential to be applied on the preparation for Rd in pharmaceutical industry. 相似文献
4.
Jin-Huan Su Jian-He Xu Hui-Lei Yu Yu-Cai He Wen-Ya Lu Guo-Qiang Lin 《Journal of Molecular Catalysis .B, Enzymatic》2009,57(1-4):278-283
A novel β-glucosidase from Fusarium proliferatum ECU2042 (FPG) was successfully purified to homogeneity with a 506-fold increase in specific activity. The molecular mass of the native purified enzyme (FPG) was estimated to be approximately 78.7 kDa, with two homogeneous subunits of 39.1 kDa, and the pI of this enzyme was 4.4, as measured by two-dimensional electrophoresis. The optimal activities of FPG occurred at pH 5.0 and 50 °C, respectively. The enzyme was stable at pH 4.0–6.5 and temperatures below 60 °C, and the deactivation energy (Ed) for FPG was 88.6 kJ mo1−1. Moreover, it was interesting to find that although the purified enzyme exhibited a very low activity towards p-nitrophenyl β-d-glucoside (pNPG), and almost no activity towards cellobiose, a relatively high activity was observed on ginsenoside Rg3. The enzyme hydrolyzed the 3-C, β-(1 → 2)-glucoside of ginsenoside Rg3 to produce ginsenoside Rh2, but did not sequentially hydrolyze the β-d-glucosidic bond of Rh2. The Km and Vmax values of FPG for ginsenoside Rg3 were 2.37 mM and 0.568 μmol (h mg protein)−1, respectively. In addition, this enzyme also exhibited significant activities towards various alkyl glucosides, aryl glucosides and several natural glycosides. 相似文献
5.
Wang CY Fang ZM Sun BS Gu LJ Zhang KQ Sung CK 《Journal of microbiology (Seoul, Korea)》2008,46(4):380-389
Esteya vermicola, as the first recorded endoparasitic fungus of pinewood nematodes, exhibits great potential as a biological agent against nematodes. However, only two strains of this species have been described so far. In this study, we identified a novel endoparasitic fungal strain, CNU 120806, isolated from infected nematodes in forest soil samples during a survey of nematophagous fungi in Korea. This strain showed similar morphological characteristics and infection mode with the two previously described strains of E. vermicola. All strains are characterized by the ability to produce two types of conidiogenous cells and conidia, and to parasitize nematodes with lunate adhesive conidia. Moreover, the CNU 120806 strain showed 100% identity with E. vermicola CBS 115803 when their partial sequences of 28S rRNA gene were compared. Molecular phylogenetic analysis further identified CNU 120806 as a strain of E. vermicola, by clustering CNU 120806 and E. vermicola CBS 115803 into a single subclade. Culture medium influenced the proportion of dimorphic CNU 120806 conidia, and further changed the adhesive and mortality rates of nematodes. The CNU 120806 strain exhibits high infection activity against nematodes on nutrient-rich PDA medium. Almost all tested nematodes were killed within 8 approximately 10 days after inoculation. This study provides justification for further research of E. vermicola, and the application and formulation of this fungus as a bio-control agent against nematodes. 相似文献
6.
Zhen Wang Chunyan Wang Min Liu Yongan Zhang Jianjie Xue Yunbo Wang 《Biocontrol Science and Technology》2011,21(12):1485-1493
Esteya vermicola, an endoparasitic fungus of pinewood nematode, exhibits great potential as a biological agent against nematodes. In this study, various mineral supplements, such as chloride salts (KCl, CaCl2, MgCl2, FeCl2, and FeCl3) and calcium salts (CaCl2, CaCO3, and CaSO4) were evaluated for their ability to enhance the growth, sporulation and virulence of E. vermicola. Of the cations tested, CaCl2 provided the greatest enhancement of growth speed and sporulation. Of the anions tested, CaCO3 produced the highest proportion of lunate conidia, and CaCl2 produced the highest adhesive rate and mortality against the nematode, Bursaphelenchus xylophilus. The optimum concentration of CaCl2 for optimization of sporulation and virulence was 0.4–0.6%. In conclusion, CaCl2 is highly effective in enhancing growth, sporulation and virulence of Esteya vermicola. 相似文献
7.
Jianjie Xue Jingang Hou Yongan Zhang Yuzhu Wang Chunyan Wang Zhen Wang Yunbo Wang Changkeun Sung 《Journal of Phytopathology》2013,161(5):353-358
Esteya vermicola is the first recorded endoparasitic fungus of the pinewood nematode, Bursaphelenchus xylophilus, which is the causal agent for the pine wilt disease. Culture on modified agar media with herbal extraction (0.5%) was found to be able to induce resistance to UV radiation, heat and drought conditions in Esteya vermicola. Herba Houttuyniae, Tatraxacum officinale and Scutellaria baicalensis Georgi exhibited the highest improvement on environmental competence of Esteya vermicola at all the tested time points under the stress conditions. In addition, improved quality and effective viability of Esteya vermicola were observed amended with the three herbal extractions in culture media. Enhanced stress resistance was associated with herbal metabolites. These findings provided a green, feasible, economical method for developing an open‐field spay application of fungal biocontrol agents against pine wilt disease. 相似文献
8.
Calcium is a known signalling molecule in eukaryotic cells and plays a central role in the regulation of many cellular processes.
In the following study, we report on the effect of external calcium treatments on the biotransformation of ginsenoside Rb1
to ginsenoside Rd by Paecilomyces bainier 229-7. We observed that the intracellular calcium content of P. bainier 229-7 mycelia was increased in response to exposure to high external Ca2+ concentrations. Both ginsenoside Rd biotransformation and β-glucosidase activity were both found to be dependent on the external
calcium concentration. At an optimal Ca2+ concentration of 45 mM, maximal ginsenoside Rd bioconversion rate of 92.44% was observed and maximal β-glucosidase activity
of 0.1778 U was reached in a 72-h biotransformation. The Ca2+ channel blocker Verapamil blocked the trans-membrane influx of calcium and decreased ginsenoside Rd biotransformatiom. In
addition, β-glucosidase activity and ginsenoside Rd content decreased by 36.0 and 29.2% respectively after a 72-h incubation
in the presence of 0.05 mM Calmodulin (CaM) antagonist Perphenazine. These results suggest that both Ca2+ channels and CaM are involved in ginsenoside Rd biotransformation via regulation of β-glucosidase activity. This is the first
report regarding the effects of calcium signal transduction on biotransformation and enzyme activity in fungi. 相似文献
9.
Chen GT Yang M Song Y Lu ZQ Zhang JQ Huang HL Wu LJ Guo DA 《Applied microbiology and biotechnology》2008,77(6):1345-1350
Preparative-scale fermentation of ginsenoside Rb1 (1) with Acremonium strictum AS 3.2058 gave three new compounds, 12β-hydroxydammar-3-one-20 (S)-O-β-d-glucopyranoside (7), 12β, 25-dihydroxydammar-(E)-20(22)-ene-3-O-β-d-glucopyranosyl-(1→2)-β-d-glucopyranoside (8), and 12β, 20 (R), 25-trihydroxydammar-3-O-β-d-glucopyranosyl-(1→2)-β-d-glucopyranoside (9), along with five known compounds, ginsenoside Rd (2), gypenoside XVII (3), ginsenoside Rg3 (4), ginsenoside F2 (5), and compound K (6). The structural elucidation of these metabolites was based primarily on one- and two-dimensional nuclear magnetic resonance
and high-resolution electron spray ionization mass spectra analyses. Among these compounds, 2–6 are also the metabolites of ginsenoside Rb1 in mammals. This result demonstrated that microbial culture parallels mammalian metabolism; therefore, A. strictum might be a useful tool for generating mammalian metabolites of related analogs of ginsenosides for complete structural identification
and for further use in pharmaceutical research in this series of compounds. In addition, the biotransformation kinetics was
also investigated. 相似文献
10.
Three new triterpenoid saponins, named ginsenoside‐Rh23 ( 1 ), ginsenoside‐Rh24 ( 2 ), and ginsenoside‐Rh25 ( 3 ), were isolated from notoginseng medicinal fungal substance. Their structures were elucidated by a combination of 1D‐ and 2D‐NMR, MS and chemical analysis. Compounds 1 – 3 exhibited moderate cytotoxic activity against MCF‐7 and NCI‐H460 cancer cell lines. 相似文献
11.
A medicinal mushroom, Phellinus linteus, was successfully cultivated using a cheese-processing waste, whey, and the optimal bioconversion conditions for the maximum
mycelial growth rate was also estimated through solid-state cultivation experiments. Response surface analysis with a face-centered
design (center point replication = 5) was applied to statistically approximate the simultaneous effects of the three variables,
i.e., substrate concentration (10–30 g lactose l−1), temperature (20–30°C), and pH (4–6), on the mycelial growth rate of P. linteus. The following is a partial cubic model where η is the mycelial growth rate (K
r
) and x
k
is the corresponding variable term (k = substrate concentration, temperature, and pH in order): η = −23.8 + 8.67 × 10−2
x
1 + 1.48x
2 + 1.77x
3 + 8.00 × 10−4
x
1
x
2 + 7.25 × 10−2
x
1
x
3 + 5.13 × 10−2
x
2
x
3 −1.28 × 10−2
x
12 –3.18 × 10−2
x
22. −2.64 × 10−1
x
32 −3.28 × 10−3
x
1
x
2
x
3 + 4.68 × 10−4
x
12
x
2. The produced response surface model proved to be significant (r
2 > 0.99, P-value <0.0001, coefficient of variation <5%) to describe the explored space. Temperature was found to be the most significant
factor of dominant effects on the mycelial growth rate, and other variables such as temperature2, pH, pH2, and (substrate concentration2 × temperature) also showed significant effects on the model output. The maximum mycelial growth rate was predicted to be
2.80 mm d−1 at 29.7 g lactose l−1, 26.2°C, and pH 5. Our results proved a good potential of whey to serve as an alternative growth medium for cultivating P. linteus mycelia. This may provide another potential for managing this nutrient-rich waste in a cost-effective way. 相似文献
12.
Juan Wang Wen-Yuan Gao Jian Zhang Tao Huang Tian-Tian Wen Lu-Qi Huang 《Acta Physiologiae Plantarum》2011,33(3):861-866
Lactoalbumin hydrolysate (LH) at 100 mg L−1 with methyl jasmonate (MJ) at 2 mg L−1 synergistically stimulated ginsenoside accumulation in Panax quinquefolium cells compared with 100 mg L−1 LH. Combination elicitors led to higher ginsenoside productivity (45.93 mg L−1) than single treatment of 100 mg L−1 LH (31.37 mg L−1). This present result will be helpful in providing a tool for enhancing the productivity of ginsenoside by Panax quinquefolium cell cultures on a commercial scale. 相似文献
13.
van Hellemond EW van Dijk M Heuts DP Janssen DB Fraaije MW 《Applied microbiology and biotechnology》2008,78(3):455-463
A gene encoding a putrescine oxidase (PuORh, EC 1.4.3.10) was identified from the genome of Rhodococcus erythropolis NCIMB 11540. The gene was cloned in the pBAD vector and overexpressed at high levels in Escherichia coli. The purified enzyme was shown to be a soluble dimeric flavoprotein consisting of subunits of 50 kDa and contains non-covalently
bound flavin adenine dinucleotide as a cofactor. From all substrates, the highest catalytic efficiency was found with putrescine
(K
M = 8.2 μM, k
cat = 26 s−1). PuORh accepts longer polyamines, while short diamines and monoamines strongly inhibit activity. PuORh is a reasonably thermostable enzyme with t
1/2 at 50°C of 2 h. Based on the crystal structure of human monoamine oxidase B, we constructed a model structure of PuORh, which hinted to a crucial role of Glu324 for substrate binding. Mutation of this residue resulted in a drastic drop (five
orders of magnitude) in catalytic efficiency. Interestingly, the mutant enzyme showed activity with monoamines, which are
not accepted by wt-PuORh.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
14.
Under optimum conditions (pH 5, 75°C, and 0.2 U purified enzyme ml−1), 4 mg ginsenoside Rd was produced from 5 mg reagent-grade ginsenoside Rb1 in 5 ml after 30 min by β-glucosidase from Thermus caldophilus GK24. Using a ginseng root extract containing 1 mg ginsenoside Rb1 ml−1 and 3.2 mg additional ginsenosides ml−1, 1.23 mg ginsenoside Rd ml−1 was produced after 18 h; the concentrations of ginsenosides Rb1, Rb2, and Rc used for ginsenoside Rd production were 0.77, 0.17, and 0.19 mg ml−1, respectively. 相似文献
15.
Hongzhen Zhang Fengli Zhang Zhiyong Li 《World journal of microbiology & biotechnology》2009,25(7):1267-1274
Gene cloning, optimized production and property of marine lipase from Bacillus pumilus B106 associated with South China Sea sponge Halichondria rugosa were investigated in this paper. A lipase gene with whole ORF encoding 215 amino acids was obtained by PCR, protein domain
prediction suggested that the deduced lipase belongs to α/β hydrolases family. Based on single factor Seriatim-Factorial test
and Plackett–Burman experimental design, the optimal medium consisted of (per l) 12.5 ml maize oil, 5.0 g beef extract, 2.0 g
PO4
3− (0.6 g KH2PO4, 1.4 g K2HPO4), 17.15 g Mg2+, 5.0 g yeast extract, 2.282 g CaCl2 and 5.0 ml Tween80 with artificial sea water. Using this optimum medium, lipase activity and cell concentration were increased
by 3.54- and 1.31-fold over that of the basal medium, respectively. This lipase showed tolerance to high salinity, pH and
temperature. About 10–20% methanol exhibited a stimulatory effect on the lipase activity, while activity was inhibited by
30–40% methanol, 2-propanol, DMSO, and ethanol. This study provides a valuable resource for marine lipase production and extends
our understanding of the possible role of sponge-associated bacteria in the biotransformation of chemical compounds for the
sponge host. 相似文献
16.
A. Pérez C. Carvajal S. Trejo M. J. Torres M. I. Martin J. C. Lorenzo C. L. Natalucci M. Hernández 《The protein journal》2010,29(4):225-233
Penduliflorain I, a new plant endopeptidase, was isolated and characterized from Hohenbergia penduliflora. Crude extract was obtained from stems. A partially purified enzyme preparation was obtained by ethanol precipitation. This
preparation showed maximum activity between pH 7.5 and 8.5, was stable at ionic strength (20% decrease in proteolytic activity
could be detected after 2 h in 0.4 M sodium chloride solution), and exhibited high thermal stability (inactivation required
heating for 20 min at 75 °C). Inhibition and activation assays indicated the cysteine nature of the enzymatic preparation.
Penduliflorain I was purified by anion exchange chromatography (Q-Sepharose HP) by FPLC system. Homogeneity was confirmed
by mass spectroscopy. Molecular mass of the enzyme was 23 412.847 Da (MALDI-TOF–MS). Kinetic parameters were determined for
PFLNA (K
m = 0.3227 mM and k
cat = 4.27 s−1). The N-terminal sequence (AVPQSIDWRDYGAVTTDKNQ) of isolated protease showed considerable similarity to other cysteine proteases
obtained from stems or fruits of different Bromeliaceae species. 相似文献
17.
The production of compound K and aglycon protopanaxadiol (APPD) from ginsenoside Rd and ginseng root extract was performed
using a recombinant β-glycosidase from Pyrococcus furiosus. The activity for Rd was optimal at pH 5.5 and 95°C with a half-life of 68 h at 95°C. β-Glycosidase converted Rb1, Rb2, Rc, and Rd to APPD via compound K. With increases in the enzyme activity, the productivities of compound K and APPD increased.
The substrate concentration was optimal at 4.0 mM Rd or 10% (w/v) ginseng root extract; 4 mM of Rd was converted to 3.3 mM compound K with a yield of 82.5% (mol/mol) and a productivity of
2,010 mg l−1 h−1 at 1 h and was hydrolyzed completely to APPD with 364 mg l−1 h−1 after 5 h. Rb1, Rb2, Rc, and Rd at 3.9 mM in 10% ginseng root extract were converted to 3.1 mM compound K with 79.5% and 1,610 mg l−1 h−1 at 1.2 h and were hydrolyzed completely to APPD with 300 mg l−1 h−1 after 6 h. The concentrations and productivities of compound K and APPD in the present study are the highest ever reported. 相似文献
18.
An DS Cui CH Sung BH Yang HC Kim SC Lee ST Im WT Kim SG 《Applied microbiology and biotechnology》2012,94(3):673-682
The gene encoding an α-l-arabinofuranosidase that could biotransform ginsenoside Rc {3-O-[β-d-glucopyranosyl-(1–2)-β-d-glucopyranosyl]-20-O-[α-l-arabinofuranosyl-(1–6)-β-d-glucopyranosyl]-20(S)-protopanaxadiol} to ginsenoside Rd {3-O-[β-d-glucopyranosyl-(1–2)-β-d-glucopyranosyl]-20-O-β-d-glucopyranosyl-20(S)-protopanaxadiol} was cloned from a soil bacterium, Rhodanobacter ginsenosidimutans strain Gsoil 3054T, and the recombinant enzyme was characterized. The enzyme (AbfA) hydrolyzed the arabinofuranosyl moiety from ginsenoside
Rc and was classified as a family 51 glycoside hydrolase based on amino acid sequence analysis. Recombinant AbfA expressed
in Escherichia coli hydrolyzed non-reducing arabinofuranoside moieties with apparent K
m values of 0.53 ± 0.07 and 0.30 ± 0.07 mM and V
max values of 27.1 ± 1.7 and 49.6 ± 4.1 μmol min−1 mg−1 of protein for p-nitrophenyl-α-l-arabinofuranoside and ginsenoside Rc, respectively. The enzyme exhibited preferential substrate specificity of the exo-type
mode of action towards polyarabinosides or oligoarabinosides. AbfA demonstrated substrate-specific activity for the bioconversion
of ginsenosides, as it hydrolyzed only arabinofuranoside moieties from ginsenoside Rc and its derivatives, and not other sugar
groups. These results are the first report of a glycoside hydrolase family 51 α-l-arabinofuranosidase that can transform ginsenoside Rc to Rd. 相似文献
19.
This study was conducted to investigate the expression patterns of pathogenesis-related proteins (chitinase, β-1,3-glucanase
and peroxidase) using activity staining of native-polyacrylamide gel electrophoresis (PAGE) and sodium dodecyl sulfate (SDS)-PAGE
during germination of rape seed (Brassica napus L. cv. Saturnin). The crude enzymes were extracted by distilled water (DW, pH 6.0) and 100 mM K-PO4 buffer (pH 7.0). The expression patterns of chitinase isozymes changed clearly on 10% native-PAGE gel with DW and K-PO4 buffer extract and on 12% SDS-PAGE gel with K-PO4 buffer extract, except for 12% SDS-PAGE conducted using DW during germination. The active bands of the chitinase isozymes
were observed as four major bands (ch1, ch2, 86, and 78 kDa) and three minor bands (71, 60, and 54 kDa) on 10% native-PAGE
gel conducted using DW and K-PO4 buffer extract. The two active bands on the 12% (w/v) SDS-PAGE gel presented as 34 and 29 kDa with DW extract, whereas one
active band of 34 kDa was observed when the K-PO4 buffer extract was used. Active bands of β-1,3-glucanase isozymes changed slightly on 10% native-PAGE gel with DW and K-PO4 buffer extract during germination. The active band of β-1,3-glucanase isozymes were shown to have a high molecular weight
(G1 and G2) on native-PAGE gel with DW extract at 0, 1, 2, and 3 days after germination, but not at 4 and 5 days. One active
band of β-1,3-glucanase presented as G1 in the K-PO4 buffer extract. Active staining of peroxidase was stronger earlier in the DW extract than K-PO4 buffer extract at 2 days. The active bands showed as P1 and P2 in both DW and K-PO4 buffer extract at 5 days after germination. 相似文献
20.
Juan Gao Yanbo Hu Yue Meng Fanlin Meng Xiaoqing Guo Nan Wang 《Biocatalysis and Biotransformation》2015,33(1):51-60
A novel ginsenoside-hydrolyzing strain was isolated from ginseng-cultivation soil in Changbai Mountain (China). The strain was identified as Cellulosimicrobium sp. 21 by 16S rDNA sequencing. Using the β-glucosidases secreted from Cellulosimicrobium sp. 21, protopanaxatriol-type ginsenoside Re was converted to the highly active neuroprotective molecule (S)-Rg2 by removal of the C-20-glucopyranosyl residue. The α-L-rhamnopyranosyl-(1→2)-β-D-glucopyranose at the C-6 position of Rg2 was not further attacked by Cellulosimicrobium sp. 21, so the transformation shows high specificity. To simplify the transformation and product-preparation process, a simple and efficient transformation system was developed in a phosphate buffer system instead of organic media. The optimum conditions for transforming ginsenoside Re into Rg2 by Cellulosimicrobium sp. 21 were determined through single-factor experiments and response surface methodology. Under the optimized conditions: transformation buffer, 50 mM phosphate buffer, at pH: 7.00; temperature: 27.6°C; substrate concentration: 0.50 mg/ml; biotransformation period: 12 h; the biotransformation efficiency reached 89.8% (molar ratio) in 2-L reaction system. This simple biotransformation with high specificity and efficiency has potential for use in Rg2 preparation in the pharmaceutical industry. 相似文献