Carnitine acetyltransferase was purified from the citric acid producingA. niger mycelium with a protein band showing a relative molecular weight of 77,000 and a pH optimum of 7.3. TheKm values for the purified enzyme for acetyl-CoA and for carnitine were 0.1 mM and 1 mM, respectively. Carnitine acetyltransferase
was located both in the mitochondria and in the cytosol. Both mitochondrial and cytosolic enzyme were purified using ammonium
sulfate precipitation, Mono Q and Superose 12 separation. Regarding the localization, except for maximum velocity, there were
no differences observed in substrate specificity and inhibition. Inhibition of the enzyme with micromolar concentrations of
Cu2+ could contribute to a greater citric acid biosynthesis. Carnitine acetyltransferase can be considered as an enzyme necessary
for the transport of acetyl groups through mitochondrial membrane in both directions. 相似文献
The polyhydroxylated ergostane‐type sterol 9 , its derivatives 10 – 15 , and the fatty acid esters 1 – 8 were isolated from a fungus strain which was collected from mangrove areas at Wenchang, Hainan Province, P. R. China, exhibited potent cytotoxic activity, and was identified as Aspergillus awamori. The structures of 1 – 15 were elucidated by spectroscopic and chemical methods. Among them, the six steryl esters 1 – 6 of fatty acids were new compounds, i.e., (3β,5α,6α,22E)‐ergosta‐7,22‐diene‐3,5,6‐triol 6‐palmitate ( 1 ), (3β,5α,6α,22E)‐ergosta‐7,22‐diene‐3,5,6‐triol 6‐stearate ( 2 ), (3β,5α,6α,22E)‐ergosta‐7,22‐diene‐3,5,6‐triol 6‐oleate ( 3 ), (3β,5α,6α,22E)‐ergosta‐7,22‐diene‐3,5,6‐triol 6‐linoleate ( 4 ), (3β,5α,6β,22E)‐ergosta‐7,22‐diene‐3,5,6‐triol 6‐palmitate ( 5 ), and (3β,5α,6β,22E)‐ergosta‐7,22‐diene‐3,5,6‐triol 6‐stearate ( 6 ). The related known fatty acids stearic acid (=octadecanoic acid) and palmitic acid (=octadecanoic acid) were also obtained. A speculative biogenetic relationship of the metabolites is proposed. The known polyhydroxylated sterols and derivatives showed cytotoxic activities, in agreement with earlier reports. The cytotoxic activities against B16 and SMMC‐7721 cell lines of the new steryl esters 1 – 6 by the MTT method were weak. 相似文献
AbstractEssential oils from aerial parts of Senecio nutans, Senecio viridis, Tagetes terniflora and Aloysia gratissima were analysed by GC-MS and their antifungal activities were assayed on toxigenic Fusarium and Aspergillus species. Sabinene (27.6?±?0.1%), α-phellandrene (15.7?±?0.3%), o-cymene (9.6?±?0.2%) and β-pinene (6.1?±?0.2%) in S. nutans, 9,10-dehydrofukinone (92.7?±?0.2%) in S. viridis, β-thujone (36.1?±?0.1%), α-thujone (32.2?±?0.2%), 1,8-cineol (10.7?±?0.1%) and sabinene (6.2?±?0.2%) in A. gratissima, and cis-tagetone (33.6?±?0.2%), cis-β-ocimene (17.1?±?0.2%), trans-tagetone (17.0?±?0.1%), cis-ocimenone (8.0?±?0.2%) and trans-ocimenone (8.2?±?0.1%) in T. terniflora. The oils showed moderate antifungal activity (1.2?mg/mL?>?MIC >0.6?mg/mL) on the Fusarium species and a weak effect on Aspergillus species. The antifungal activity was associated on F. verticillioides to the high content of cis-tagetone, trans-tagetone, cis-β-ocimene, cis-ocimenone, trans-ocimenone and on F. graminearum due to the total content of oxygenated sesquiterpenes and 9,10- dehydrofukinone. The oil of S. viridis synergized the effect of fungicides and food preservatives on F. verticillioides. 相似文献
Rapid and sensitive determination of citric acid in fermentation media by pyrolysis mass spectrometry (Py–MS) is proposed. Owing to high specificity of this method, distinguishing the citric acid from the matrix and by-products formed in the Krebs cycle is possible. Selected ion monitoring (SIM) mode is used for quantitative measurements, in which mass to charge (m/z) values of 175 of citric acid and 138 of 3-nitroaniline as internal standard are chosen. Limit of detection (LOD) for this method has been found to be 1 ng ml−1 and the linear working range was 10 ng ml−1–100 mg ml−1. Relative standard deviation (R.S.D.) of the method for five replicates was 0.84%. Results of Py–MS are compared with those obtained by UV–vis spectrophotometric method. Also, factor analysis is used for evaluating the influence of pH, molasses concentration, time and shaker intensity on the production of citric acid by Aspergillus niger. 相似文献
Inhibition of radial growth and spore germination of Aspergillus niger in media with added chitosan were detected. The highest radial growth inhibition (73%) was determined at 24 h with 3 g · L?1 of chitosan, and the percent inhibition of spore germination was 40% after 13 h of inoculation. Further, the CC50, that is, the concentration at which spore germination is inhibited by 50%, was estimated by probit analysis (3.5 g · L?1). The activation energies, EA were estimated by an Arrhenius model in control and amended chitosan media, obtaining 35.6 and 36.6 kcal · mol?1, respectively. These values were in the same order of magnitude because chitosan as inhibitor was more effective at low temperature (≤ 18 °C). Hence synergism of temperature and chitosan were only observed at 12 and 18 °C. Therefore, the maximal percentage of germinated spores, Smax was also affected by low temperatures in chitosan‐amended media with estimated values lower than 70% at temperatures < 37 °C whereas in control media Smax reached values close to 100%. Scanning electron micrographs showed that chitosan produced spore aggregation and morphological anomalies affecting swelling, germ tube emergence, and polarization.
Germinated spores percentages of Aspergillus niger in Czapeck media at several chitosan concentrations and 30 °C. 相似文献
Convenient expression systems for efficient heterologous production of different laccases are needed for their characterization
and application. The laccase cDNAs lcc1 and lcc2 from Trametes versicolor were expressed in Pichia pastoris and Aspergillus niger under control of their respective glyceraldehyde-3-phosphate dehydrogenase promoters and with the native secretion signal
directing catalytically active laccase to the medium. P. pastoris batch cultures in shake-flasks gave higher volumetric activity (1.3 U/L) and a better activity to biomass ratio with glucose
than with glycerol or maltose as carbon source. Preliminary experiments with fed-batch cultures of P. pastoris in bioreactors yielded higher activity (2.8 U/L) than the shake-flask experiments, although the levels remained moderate
and useful primarily for screening purposes. With A. niger, high levels of laccase (2700 U/L) were produced using a minimal medium containing sucrose and yeast extract. Recombinant
laccase from A. nigher harboring the lcc2 cDNA was purified to homogeneity and it was found to be a 70-kDa homogeneous enzyme with biochemical and catalytic properties
similar to those of native T. versicolor laccase A. 相似文献
Production of cellulolytic enzymes on bagasse under solid state fermentation by coculture ofAspergillus ellipticus andAspergillus fumigatus was studied. Cocultivation ofA. ellipticus andA. fumigatus showed improved hydrolytic and Β-glucosidase activities as compared to the occasions when they were used separately. Various
pretreatment methods were used to make cellulose accessible to enzymatic attack. Best results were obtained through pretreatment
with 2% (w/v) calcium hydroxide. Maximum enzyme production was obtained after 8 d of fermentation process. 相似文献
The aliphatic heterocycles piperidine and morpholine are core structures of well-known antifungals such as fenpropidin and fenpropimorph, commonly used as agrofungicides, and the related morpholine amorolfine is approved for the treatment of dermal mycoses in humans. Inspired by these lead structures, we describe here the synthesis and biological evaluation of 4-aminopiperidines as a novel chemotype of antifungals with remarkable antifungal activity. A library of more than 30 4-aminopiperidines was synthesized, starting from N-substituted 4-piperidone derivatives by reductive amination with appropriate amines using sodium triacetoxyborohydride. Antifungal activity was determined on the model strain Yarrowia lipolytica, and some compounds showed interesting growth-inhibiting activity. These compounds were tested on 20 clinically relevant fungal isolates (Aspergillus spp., Candida spp., Mucormycetes) by standardized microbroth dilution assays. Two of the six compounds, 1-benzyl-N-dodecylpiperidin-4-amine and N-dodecyl-1-phenethylpiperidin-4-amine, were identified as promising candidates for further development based on their in vitro antifungal activity against Candida spp. and Aspergillus spp. Antifungal activity was determined for 18 Aspergillus spp. and 19 Candida spp., and their impact on ergosterol and cholesterol biosynthesis was determined. Toxicity was determined on HL-60, HUVEC, and MCF10A cells, and in the alternative in vivo model Galleria mellonella. Analysis of sterol patterns after incubation gave valuable insights into the putative molecular mechanism of action, indicating inhibition of the enzymes sterol C14-reductase and sterol C8-isomerase in fungal ergosterol biosynthesis. 相似文献
In the previous report on bioactive secondary metabolites from the sponge-associated fungus Aspergillus versicolor (Vuill) Tirab, the bioassay guiding fractionation led to isolation of six new compounds with unusual skeleton based on chromone ring system from the inculated fungus which was isolated from fresh samples of marine sponge Xestospongia exigua, collected along coast line of Bali, Indonesia in 19971. In the continuation of our chemical investigation on the marine fungus, four compou… 相似文献
Different factors affecting the efficiency of the ultrasonic depolymerization of the high-molecular-weight carboxymethylated chitin–glucan prepared from the fungal mycelium of Aspergillus niger have been investigated. The influence of the following parameters was examined: concentration of the chitin–glucan complex, duration of ultrasonic irradiation, reaction temperature and volume of the ultrasonicated solution. The optimized conditions for the efficient ultrasonic depolymerization include: polysaccharide concentration – 0.2 mg ml−1; volume of the sonicated solution – 25 ml; duration of the sonication – 10 min; and constant cooling of the sonicated sample in an ice–water bath. 相似文献