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1.
Potent antioxidative hydroxyflavanones were produced with Aspergillus saitoi from hesperidin or naringin, which are flavanone glycosides in citrus fruit with weak antioxidative activity. The hydroxyflavanone produced from hesperidin was identified as 8-hydroxyhesperetin (8-HHE), a novel substance, and those from naringin were identified as carthamidin (6-hydroxynaringenin) and isocarthamidin (8-hydroxynaringenin) by FAB-MS, 1H-NMR and 13C-NMR analyses. The antioxidative activity of these hydroxyflavanones was examined by using the free radical-scavenging system of 1,1-diphenyl-2-picrylhydrazyl (DPPH) and the methyl linoleate oxidation system. The hydroxyflavanones (8-HHE, carthamidin, and isocarthamidin) exhibited stronger activity than the flavanone glycosides (hesperidin or naringin) and their aglycones (hesperetin or naringenin). The activity of 8-HHE and isocarthamidin was comparable to that of α-tocopherol, and that of carthamidin was weaker than that of isocarthamidin. The hydroxyflavanones, which were hydroxylated on A ring of flavanone by Aspergillus saitoi, were obtained as potent antioxidants.  相似文献   

2.
Potent antioxidative hydroxyflavanones were produced with Aspergillus saitoi from hesperidin or naringin, which are flavanone glycosides in citrus fruit with weak antioxidative activity. The hydroxyflavanone produced from hesperidin was identified as 8-hydroxyhesperetin (8-HHE), a novel substance, and those from naringin were identified as carthamidin (6-hydroxynaringenin) and isocarthamidin (8-hydroxynaringenin) by FAB-MS, 1H-NMR and 13C-NMR analyses. The antioxidative activity of these hydroxyflavanones was examined by using the free radical-scavenging system of 1,1-diphenyl-2-picrylhydrazyl (DPPH) and the methyl linoleate oxidation system. The hydroxyflavanones (8-HHE, carthamidin, and isocarthamidin) exhibited stronger activity than the flavanone glycosides (hesperidin or naringin) and their aglycones (hesperetin or naringenin). The activity of 8-HHE and isocarthamidin was comparable to that of alpha-tocopherol, and that of carthamidin was weaker than that of isocarthamidin. The hydroxyflavanones, which were hydroxylated on A ring of flavanone by Aspergillus saitoi, were obtained as potent antioxidants.  相似文献   

3.
Biosorption is an eco-friendly and cost-effective method for treating the dye house effluents. Aspergillus niger and Trichoderma sp. were cultivated in bulk and biomasses used as biosorbents for the biosorption of an azo dye Orange G. Batch biosorption studies were performed for the removal of Orange G from aqueous solutions by varying the parameters like initial aqueous phase pH, biomass dosage, and initial dye concentration. It was found that the maximum biosorption was occurred at pH 2. Experimental data were analyzed by model equations such as Langmuir and Freundlich isotherms, and it was found that both the isotherm models best fitted the adsorption data. The monolayer saturation capacity was 0.48 mg/g for Aspergillus niger and 0.45 mg/g for Trichoderma sp. biomasses. The biosorption kinetic data were tested with pseudo first-order and pseudo second-order rate equations, and it was found that the pseudo second-order model fitted the data well for both the biomasses. The rate constant for the pseudo second-order model was found to be 10–0.8 (g/mg min−1) for Aspergillus niger and 8–0.4 (g/mg min−1) for Trichoderma sp. by varying the initial dye concentrations from 5 to 25 mg/l. It was found that the biomass obtained from Aspergillus niger was a better biosorbent for the biosorption of Orange G dye when compared to Trichoderma sp.  相似文献   

4.
Flavonoids glycosylated with UDP-glucuronic acid and UDP-xylose are spatially distributed in nature. To produce these glycosides, E. coli was engineered to overexpress biosynthetic gene clusters of UDP-sugars (galU from E. coli K12, UDP-glucose dehydrogenase (calS8), and UDP-glucuronic acid decarboxylase (calS9) from Micromonospora echinospora spp. calichensis). Flavonoids were glycosylated by overexpression of the glycosyltransferase gene (atGt-5) from Arabidopsis thaliana. Finally, metabolically engineered host E. coli (US89Gt-5) was generated. Production of flavonoid glycosides was observed in a biotransformation system consisting of flavonoids (naringenin and quercetin) exogenously fed to host cells. The glycosylated derivatives 7-O-glucuronyl naringenin (m/z+ 449), 7-O-xylosyl naringenin (m/z+ 405), and 7-O-glucuronyl quercetin (m/z+ 479) were detected and confirmed by ESI-MS/MS, ESI-MS/MS and LC/MS-MS analysis, respectively.  相似文献   

5.
An oleandomycin glycosyltransferase (OleD GT) gene from Streptomyces antibioticus was functionally expressed in Escherichia coli BL21 (DE3) with various molecular chaperones. The purified recombinant OleD GT catalyzed glycosylation of various flavonoids: apigenin, chrysin, daidzein, genistein, kaempferol, luteolin, 4-methylumbelliferone, naringenin, quercetin and resveratrol with UDP–glucose. 4.6 μg OleD GT was readily immobilized onto 1 mg hybrid nanoparticles of Fe3O4/silica/NiO on the basis of the affinity between His-tag and NiO nanoparticles with retention of 90% activity. In batch reaction, more than 90% naringenin (20 μM) was converted to its glycoside in 5 h. The immobilized OleD GT was efficiently reused for seven times whilst maintaining >60% of the residual activity in repeated glycosylation of naringenin.  相似文献   

6.
Flavonoid glycosides are known for their medicinal properties and potential use as natural sweeteners. In this study, Saccharomyces cerevisiae expressing a flavonoid glucosyltransferase from Dianthus caryophyllus was used as a whole-cell biocatalyst. The yeast system’s performance was characterized using the flavanone naringenin as a model substrate for the production of naringenin glycosides. It was found that final naringenin glycoside yields increased in a dose-dependent manner with increasing initial naringenin substrate concentrations. However, naringenin concentrations >0.5 mM did not give further enhancements in glycoside yield. In addition, a method for controlling overall selectivity was discovered where the glucose content in the culture medium could be altered to control the selectivity, making either naringenin-7-O-glucoside (N7O) or naringenin-4′-O-glucoside (N4O) the major products. The highest yields achieved were 87 mg/L of N7O and 82 mg/L of N4O using 40MSGI and 2xMSGI media, respectively. The effects of two intermediates involved in UDP-glucose biosynthesis, uridine 5′-monophosphate (UMP) and orotic acid, on glycoside yields were also determined. Addition of UMP to the culture medium significantly decreased glycoside yield. In contrast, addition of orotic acid to the culture medium significantly enhanced the glycoside yield and shifted the selectivity toward N7O. The highest naringenin glycoside yield achieved using 10 mM orotic acid in the 40MSGI media was 155 mg/L, a 71% conversion of substrate to product.  相似文献   

7.
Commercial lipase preparations and mycelium bound lipase from Aspergillus niger NCIM 1207 were used for esterification of acetic acid with isoamyl alcohol to obtain isoamyl acetate. The esterification reaction was carried out at 30°C in n-hexane with shaking at 120 rpm. Initial reaction rates, conversion efficiency and isoamyl acetate concentration obtained using Novozyme 435 were the highest. Mycelium bound lipase of A. niger NCIM 1207 produced maximal isoamyl acetate formation at an alcohol/acid ratio of 1.6. Acetic acid at higher concentrations than required for the critical alcohol/acid ratio lower than 1.3 and higher than 1.6 resulted in decreased yields of isoamyl acetate probably owing to lowering of micro-aqueous environmental pH around the enzyme leading to inhibition of enzyme activity. Mycelium bound A. niger lipase produced 80 g/l of isoamyl acetate within 96 h even though extremely less amount of enzyme activity was used for esterification. The presence of sodium sulphate during esterification reaction at higher substrate concentration resulted in increased conversion efficiency when we used mycelium bound enzyme preparations of A. niger NCIM 1207. This could be due to removal of excess water released during esterification reaction by sodium sulphate. High ester concentration (286.5 g/l) and conversion (73.5%) were obtained within 24 h using Novozyme 435 under these conditions.  相似文献   

8.
West TP 《Biotechnology letters》2011,33(12):2463-2467
The ability of Aspergillus strains to utilize thin stillage to produce malic acid was compared. The highest malic acid was produced by Aspergillus niger ATCC 9142 at 17 g l−1. Biomass production from thin stillage was similar with all strains but ATCC 10577 was the highest at 19 g l−1. The highest malic acid yield (0.8 g g−1) was with A. niger ATCC 9142 and ATCC 10577 on the stillage. Thus, thin stillage has the potential to act as a substrate for the commercial production of food-grade malic acid by the A. niger strains.  相似文献   

9.
Transforming naringin using the mycelium of Trichoderma harzianum CGMCC 1523 produces two metabolites, 3′,4′,5,7-tetrahydroxy flavanone-7-rhamnoglucoside (3′-OHN) and 3′,4′,5′,5,7-pentahydroxy flavanone-7-rhamnoglucoside (3′,5′-DOHN), both of which were characterized by ESI–MS, 1H NMR and 13C NMR analyses. The time course of the biotransformation by T. harzianum showed that 3′-OHN and 3′,5′-DOHN appeared simultaneously at 6 h, and the conversion yield (32.6%) of 3′,5′-DOHN was higher (10.6%) than that of 3′-OHN at 56 h. The optimal biotransformation temperature was 30 °C, the optimal pH was 5.0, and the optimal concentration of naringin was 400 mg/l. The bigger volume of biotransformation mixture and lower shaking speed did not favor hydroxylation reactions. The radical scavenging activity of naringin at 2000 μM was 11.1%, whereas activity of 3′-OHN at 100 μM could reach 38.4%, which is 68.6 times more than naringin. Antioxidative activity of 3′,5′-DOHN was increased 13.5% at 100 μM compared to 3′-OHN.  相似文献   

10.
Aims: To evaluate the potential of apple pomace (AP) supplemented with rice husk for hyper citric acid production through solid‐state fermentation by Aspergillus niger NRRL‐567. Optimization of two key parameters, such as moisture content and inducer (ethanol and methanol) concentration was carried out by response surface methodology. Methods and Results: In this study, the effect of two crucial process parameters for solid‐state citric acid fermentation by A. niger using AP waste supplemented with rice husk were thoroughly investigated in Erlenmeyer flasks through response surface methodology. Moisture and methanol had significant positive effect on citric acid production by A. niger grown on AP (P < 0·05). Higher values of citric acid on AP by A. niger (342·41 g kg?1 and 248·42 g kg?1 dry substrate) were obtained with 75% (v/w) moisture along with two inducers [3% (v/w) methanol and 3% (v/w) ethanol] with fermentation efficiency of 93·90% and 66·42%, respectively depending upon the total carbon utilized after 144 h of incubation period. With the same optimized parameters, conventional tray fermentation was conducted. The citric acid concentration of 187·96 g kg?1 dry substrate with 3% (v/w) ethanol and 303·34 g kg?1 dry substrate with 3% (v/w) methanol were achieved representing fermentation efficiency of 50·80% and 82·89% in tray fermentation depending upon carbon utilization after 120 h of incubation period. Conclusions: Apple pomace proved to be the promising substrate for the hyper production of citric acid through solid‐state tray fermentation, which is an economical technique and does not require any sophisticated instrumentation. Significance and Impact of the Study: The study established that the utilization of agro‐industrial wastes have positive repercussions on the economy and will help to meet the increasing demands of citric acid and moreover will help to alleviate the environmental problems resulting from the disposal of agro‐industrial wastes.  相似文献   

11.
The microbial hydroxylation of 10-deoxoartemisinin was investigated with the aim of obtaining preparative yields of hydroxy derivatives. During 14 d at 28°C and pH 6.5 Aspergillus niger transformed 10-deoxoartemisinin (500 mg l–1) to 15-hydroxy-10-deoxoartemisinin (26%) and 7-hydroxy-10-deoxoartemisinin (69%).  相似文献   

12.
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   

13.
A general in vitro cloning system was established for four Helleborus species: H. argutifolius, H. foetidus, H. niger and H. orientalis. The plant material was introduced in vitro from axillary buds. A Murashige and Skoog (MS)—based medium (Murashige and Skoog 1962) was used supplemented with 2% (w/v) sucrose, 2-isopentenyladenine (2-iP) and 6-benzylaminopurine (BA). Multiplication rates depended on the genotype and varied from 1.3 for H. foetidus till 3.8 for H. niger. The first results showed that the rooting phase could be done ex vitro. Rooting was induced by a drench for one week in a solution of indole-3-butyric acid (IBA -3 mg l−1) and 1-naphthaleneacetic acid (NAA-1 mg l−1) at 5°C.  相似文献   

14.
Rare sugars have many applications in food industry, as well as pharmaceutical and nutrition industries. Xylitol dehydrogenase (XDH) can be used to synthesize various rare sugars enzymatically. However, the immobilization of XDH has not been performed to improve the industrial production of rare sugars. In this study, silica nanoparticles which have high immobilization efficiency were selected from among several carriers for immobilization of recombinant Rhizobium etli CFN42 xylitol dehydrogenase (ReXDH) and subjected to characterization. Among four different chemical modification methods to give different functional groups, the silica nanoparticle derivatized with epoxy groups showed the highest immobilization efficiency (92%). The thermostability of ReXDH was improved more than tenfold by immobilization on epoxy-silica nanoparticles; the t 1/2 of the ReXDH was enhanced from 120 min to 1,410 min at 40 °C and from 30 min to 450 min at 50 °C. The K m of ReXDH was slightly altered from 17.9 to only 19.2 mM by immobilization. The immobilized ReXDH had significant reusability, as it retained 81% activity after eight cycles of batch conversion of xylitol into l-xylulose. A ∼ 71% conversion and a productivity of 10.7 g h-1 l-1 were achieved when the immobilized ReXDH was employed to catalyze the biotransformation of xylitol to l-xylulose, a sugar that has been used in medicine and in the diagnosis of hepatitis. These results suggest that immobilization of ReXDH onto epoxy-silica nanoparticles has potential industrial application in rare sugar production.  相似文献   

15.
Two oxygen-containing monoterpene substrates, menthol or geraniol (25 mg l−1), were added to Anethum graveolens hairy root cultures to evaluate the influence of the biotransformation capacity on growth and production of volatile compounds. Growth was assessed by the dissimilation method and by fresh and dry weight measurement. The volatiles were analyzed by GC and GC–MS. The total constitutive volatile component was composed, in more than 50%, by falcarinol (17–52%), apiole (11–24%), palmitic acid (7–16%), linoleic acid (4–9%), myristicin (4-8%) and n-octanal (2-5%). Substrate addition had no negative influence on growth. The relative amount of menthol quickly decreased 48 h after addition, and the biotransformation product menthyl acetate was concomitantly formed. Likewise, the added geraniol quickly decreased over 48 h alongside with the production of the biotransformation products. The added geraniol was biotransformed in 10 new products, the alcohols linalool, α-terpineol and citronellol, the aldehydes neral and geranial, the esters citronellyl, neryl and geranyl acetates and linalool and nerol oxides. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.  相似文献   

16.
The operational stabilities of nitrilases from Aspergillus niger K10 and Fusarium solani O1 were examined with 4-cyanopyridine as the substrate in continuous-stirred membrane reactors (CSMRs). The former enzyme was fairly stable at 30 °C with a deactivation constant (k d) and enzyme half-life of 0.014 h−1 and 50 h, respectively, but the latter exhibited an even higher stability characterized by k d = 0.008 h−1 and half-life of 87 h at 40 °C. Another advantage of this enzyme was its high chemoselectivity, i.e., selective transformation of nitriles into carboxylic acids, while the amide formed a high ratio of A. niger K10 nitrilase product. High conversion rates (>90%) were maintained for about 52 h using the nitrilase from F. solani O1 immobilized in cross-linked enzyme aggregates (CLEAs). The purity of isonicotinic acid was increased from 98% to >99.9% by using two CSMRs connected in series, the first one containing the F. solani O1 nitrilase and the second the amidase from Rhodococcus erythropolis A4 (both enzymes as CLEAs), the amidase hydrolyzing the by-product isonicotinamide.  相似文献   

17.
A closed gas loop bioprocess was developed to improve fungal biotransformation of monoterpenes. By circulating monoterpene-saturated process gas, the evaporative loss of the volatile precursor from the medium during the biotransformation was avoided. Penicillium solitum, isolated from kiwi, turned out to be highly tolerant towards monoterpenes and to convert α-pinene to a range of products including verbenone, a valuable aroma compound. The gas loop was mandatory to reproduce the production of 35 mg L−1 verbenone obtained in shake flasks and also in the bioreactor. Penicillium digitatum DSM 62840 regioselectively converted (+)-limonene to the aroma compound α-terpineol, but shake flask cultures revealed a pronounced growth inhibition when initial concentrations exceeded 1.9 mM. In the bioreactor, toxic effects on P. digitatum during biotransformation were alleviated by starting a sequential feeding of non-toxic limonene portions after a preceding growth phase. Closing the precursor-saturated gas loop during the biotransformation allowed for an additional replenishment of limonene via the gas phase. The gas loop system led to a maximum α-terpineol concentration of 1,009 mg L−1 and an average productivity of 8–9 mg L−1 h−1 which represents a doubling of the respective values previously reported. Furthermore, a molar conversion yield of up to 63% was achieved. M. Pescheck and M. A. Mirata have contributed equally to this work.  相似文献   

18.
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   

19.

Steroid C25 dehydrogenase (S25DH) from Sterolibacterium denitrificans Chol-1S is a molybdenum oxidoreductase belonging to the so-called ethylbenzene dehydrogenase (EBDH)-like subclass of DMSO reductases capable of the regioselective hydroxylation of cholesterol or cholecalciferol to 25-hydroxy products. Both products are important biologically active molecules: 25-hydroxycholesterol is responsible for a complex regulatory function in the immunological system, while 25-hydroxycholecalciferol (calcifediol) is the activated form of vitamin D3 used in the treatment of rickets and other calcium disorders. Studies revealed that the optimal enzymatic synthesis proceeds in fed-batch reactors under anaerobic conditions, with 6–9 % (w/v) 2-hydroxypropyl-β-cyclodextrin as a solubilizer and 1.25–5 % (v/v) 2-methoxyethanol as an organic co-solvent, both adjusted to the substrate type, and 8–15 mM K3[Fe(CN)6] as an electron acceptor. Such thorough optimization of the reaction conditions resulted in high product concentrations: 0.8 g/L for 25-hydroxycholesterol, 1.4 g/L for calcifediol and 2.2 g/L for 25-hydroxy-3-ketosterols. Although the purification protocol yields approximately 2.3 mg of pure S25DH from 30 g of wet cell mass (specific activity of 14 nmol min−1 mg−1), the non-purified crude extract or enzyme preparation can be readily used for the regioselective hydroxylation of both cholesterol and cholecalciferol. On the other hand, pure S25DH can be efficiently immobilized either on powder or a monolithic silica support functionalized with an organic linker providing NH2 groups for enzyme covalent binding. Although such immobilization reduced the enzyme initial activity more than twofold it extended S25DH catalytic lifetime under working conditions at least 3.5 times.

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20.
Plant cell cultures of Peganum harmala converted geranyl acetate to geraniol. Although the reaction started immediately after feeding, there was disappearance of both product and substrate. Geranyl acetate at 100 mg l–1 when fed to 100 ml Peganum harmala suspensions (16% packed cell volume) was completely used within 24 h without accumulation of any product. Similarly, linalyl acetate and its biotransformation products, linalool and -terpineol, disappeared. Controlled-release polymer discs made from poly-2-hydroxyethyl methacrylate and containing concentrations of geranyl acetate or linalyl acetate produced greatly extended concentrations of these substrates and their biotransformation products (from about 1 day to over 12 days). The concentrations of substrates remained at around 5 mg l–1throughout the experiments, while the concentrations of biotransformation products increased from 10 mg l–1to 55.5 mg l–1 for geraniol, from 5 mg l–1 to 14 mg l–1 for linalool, and 5 mg l–1 to 12 mg l–1 for -terpineol compared to the control value. Also low concentrations (30–200 g/disc) of product were taken up by the polymer over 10 days.  相似文献   

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