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1.
The effect of agitation and aeration on the growth and antibiotic production by Xenorhabdus nematophila YL001 grown in batch cultures were investigated. Efficiency of aeration and agitation was evaluated through the oxygen mass
transfer coefficient (K
L
a). With increase in K
L
a, the biomass and antibiotic activity increased. Activity units of antibiotic and dry cell weight were increased to 232 U ml−1 and 19.58 g l−1, respectively, productivity in cell and antibiotic was up more than 30% when K
L
a increased from 115.9 h−1 to 185.7 h−1. During the exponential growth phase, DO concentration was zero, the oxygen supply was not sufficient. So, based on process
analysis, a three-stage oxygen supply control strategy was used to improved the DO concentration above 30% by controlling
the agitation speed and aeration rate. The dry cell weight and activity units of antibiotic were further increased to 24.22 g l−1 and 249 U ml−1, and were improved by 24.0% and 7.0%, compared with fermentation at a constant agitation speed and a constant aeration rate
(300 rev min−1, 2.5 l min−1). 相似文献
2.
da Silva TL Mendes A Mendes RL Calado V Alves SS Vasconcelos JM Reis A 《Journal of industrial microbiology & biotechnology》2006,33(6):408-416
The potential use of n-dodecane as an oxygen vector for enhancement of Crypthecodinium cohnii growth and docosahexaenoic acid (DHA) production was studied. The volumetric fraction of oxygen vector influenced the gas–liquid volumetric mass transfer coefficient k
L
a positively. The k
L
a increased almost linearly with the increase of volumetric fraction of n-dodecane up to 1%. The stirring rate showed a higher influence on the k
L
a than the aeration rate. The effects of this hydrocarbon on C. cohnii growth and DHA production were then investigated. A control batch fermentation without n-dodecane addition (CF) and a batch fermentation where n-dodecane 1% (v/v) was added (DF) were carried out simultaneously under the same experimental conditions. It was found that, before 86.7 h of fermentation, the biomass concentration, the specific growth rate, the DHA, and total fatty acids (TFA) production were higher in the CF. After this fermentation time, the biomass concentration, the DHA and TFA production were higher in the DF. The highest DHA content of biomass (6.14%), DHA percentage of TFA (51%), and DHA production volumetric rate r
DHA (9.75 mg l−1 h−1) were obtained at the end of the fermentation with n-dodecane (135.2 h). The dissolved oxygen tension (DOT) was always higher in the DF, indicating a better oxygen transfer due to the oxygen vector presence. However, since the other C. cohnii unsaturated fatty acids percentages did not increase with the oxygen availability increase due to the n-dodecane presence, a desaturase oxygen-dependent mechanism involved in the C. cohnii DHA biosynthesis was not considered to explain the DHA production increase. A selective extraction through the n-dodecane was suggested. 相似文献
3.
Enhancement of oxygen mass transfer in stirred bioreactors using oxygen-vectors. 1. Simulated fermentation broths 总被引:4,自引:0,他引:4
Oxygen mass transfer represents the most important parameter involved in the design and operation of mixing-sparging equipment for bioreactors. It can be described and analyzed by means of the mass transfer coefficient, kLa. The kLa values are affected by many factors such as geometrical and operational characteristics of the vessels, media composition, type, concentration and microorganism morphology, and biocatalysts properties. The efficiency of oxygen transfer could be enhanced by adding oxygen-vectors in broths, such as hydrocarbons or fluorocarbons, without increasing the energy consumption for mixing or aeration. The experimental results obtained for simulated broths indicated a considerable increase of kLa in the presence of n-dodecane, and the existence of a certain value of n-dodecane concentration that corresponds to a maximum mass transfer rate of oxygen. The magnitude of the positive effect of n-dodecane depends both on the broths characteristics and operational conditions of the bioreactor.Notation d stirrer diameter, mm - d oxygen electrode diameter, mm - D bioreactor diameter, mm - h distance from the inferior stirrer to the bioreactor bottom, mm - H bioreactor height, mm - kLa oxygen mass transfer coefficient, s-1 - l impeller blade length, mm - I oxygen electrode immersed length, mm - P power consumption for mixing of non-aerated broths, W - Pa power consumption for mixing of aerated broths, W - (Pa/V) specific power input, W/m3 - s baffle width, mm - vS superficial air velocity, m/s - V volume of medium, m3 - w impeller blade height, mm - volumetric fraction of oxygen-vector - a apparent viscosity, Pa*s - density, kg/m3 相似文献
4.
Aguedo M Gomes N Garcia EE Waché Y Mota M Teixeira JA Belo I 《Biotechnology letters》2005,27(20):1617-1621
Yarrowia lipolytica converts methyl ricinoleate to γ-decalactone, a high-value fruity aroma compound. The highest amount of 3-hydroxy-γ-decalactone
produced by the yeast (263 mg l-1) occurred by increasing the kLa up to 120 h−1 at atmospheric pressure; above it, its concentration decreased, suggesting a predominance of the activity of 3-hydroxyacyl-CoA
dehydrogenase. Cultures were grown under high-pressure, i.e., under increased O2 solubility, but, although growth was accelerated, γ-decalactone production decreased. However, by applying 0.5 MPa during
growth and biotransformation gave increased concentrations of dec−2-en-4-olide and dec-3-en-4-olide (70 mg l−1). 相似文献
5.
Ducros E Ferrari M Pellegrino M Raspanti C Bogni C 《Bioprocess and biosystems engineering》2009,32(1):143-148
The modified rotating simplex method has been successfully used to determine the best combination of agitation rate and aeration
rate for maximum production of extracellular proteases by Staphylococcus aureus mutant RC128, in a stirred tank bioreactor operated in a discontinuous way. This mutant has shown altered exoprotein production,
specially enhanced protease production. Maximum production of proteases (15.28 UP/ml), measured using azocasein as a substrate,
was obtained at exponential growth phase when the bioreactor was operated at 300 rpm and at 2 vvm with a volumetric oxygen
transfer coefficient (K
L
a) of 175.75 h−1. These conditions were found to be more suitable for protease production. 相似文献
6.
Giandra Volpato Rafael C. Rodrigues Júlio Xandro Heck Marco Antônio Záchia Ayub 《Biotechnology and Bioprocess Engineering》2009,14(1):105-111
The principal objectives of this study were to evaluate the kinetics of lipase production by Staphylococcus warneri EX17 under different oxygen volumetric mass transfer coefficients (kLa) and pH conditions in submerged bioreactors, using glycerol (a biodiesel by-product) as a carbon source. Cultivations were
conducted at different kLa (26, 38, 50, and 83 h−1) and pH values (6.0, 7.0, and 8.0). The optimal kLa and pH were 38 h−1 and 7.0, respectively. Under these conditions, the maximal cell production obtained was 8.0 g/L, and the volumetric and specific
lipase production reached high levels of activity, approximately 800 U/L and 150 U/g cell, respectively, after 12 h of cultivation.
This result was approximately five times higher than that obtained in the shake flask cultures. The relationship between cell
growth and lipase production was found to be associated with growth by the Luedeking-Piret model. 相似文献
7.
Jesús Adolfo Jiménez Nieves Alonso-Blázquez Dolores López-Vela Cristina Celestino Mariano Toribio Jesus Alegre 《In vitro cellular & developmental biology. Plant》2011,47(5):578-588
Somatic embryogenesis can be induced in the leaves of cork oak (Quercus suber L.) trees. The use of this propagation system in multivarietal forestry requires the mass production of cloned plants at
low cost. Investigations were made into the influence of three types of Erlenmeyer flask and three orbiting speeds (60, 110,
and 160 rpm) on oxygen transfer rate (KL
a), the shear force index (SFI), biomass production, and the proliferation of embryogenic clumps (EMCs) in cultures during
the proliferation phase. KL
a varied between 0.11 and 1.47 h−1 without biomass production being limited by oxygen availability. The EMCs grew even in hypoxic conditions, although the suppression
of gaseous exchange strongly reduced biomass production. Cultures with different levels of hydrodynamic stress and SFI values
(1.4·10−3–8.8·10−3 cm min−1) were obtained. Proliferation rates of EMCs increased with agitation rate and the SFI. The largest number of EMCs was obtained
in baffled flasks agitated at 160 rpm (KL
a of 1.47 h−1, and SFI of 8.8·10−3 cm min−1) with mild hydrodynamic stress enhancing growth. Biomass production increased with agitation and hydrodynamic stress, but
only when the SFI value was below 5·10−3 cm min−1. The greatest biomass production was obtained in smooth 100 ml flasks agitated at 160 rpm. The differentiation of embryos
was favoured by the lowest KL
a (0.11 h−1) and SFI (1.40·103 cm min−1) values, achieved using these flasks when agitated at 60 rpm. 相似文献
8.
Diversity of juvenile fish assemblages in the pelagic waters of Lebanon (eastern Mediterranean) 总被引:1,自引:0,他引:1
Oxygen consumption rates of nauplii of the brine shrimp Artemia franciscana Kellogg 1906 were determined over a range of salinities from 10 to 110 ppm, in temperatures from 0 to 30°C, using a multi-factorial
design. The oxygen micro-sensors employed have a fast response time and are capable of accurately measuring oxygen concentrations
at temperatures well below 0°C. Oxygen uptake rate ranged from 0.03 to 0.66 μmol O2 mg−1 h−1 and was sensitive to changes in both salinity and temperature. Temperature was the dominant factor affecting oxygen consumption
rates, which showed a significant increase with increasing temperature. A slight decrease was measured in oxygen consumption
with increasing salinity related to differential solubility of oxygen in waters of different salinities. Thermal sensitivity
of oxygen consumption determined from calculations of Q
10, indicated physiological adaptation of Artemia nauplii to the ranges of temperatures tested.
Handling editor: A. van Kerchove 相似文献
9.
The ability of an ecosystem to retain anthropogenic nitrogen (N) deposition is dependent upon plant and soil sinks for N,
the strengths of which may be altered by chronic atmospheric N deposition. Sugar maple (Acer saccharum Marsh.), the dominant overstory tree in northern hardwood forests of the Lake States region, has a limited capacity to take
up and assimilate NO3−. However, it is uncertain whether long-term exposure to NO3− deposition might induce NO3− uptake by this ecologically important overstory tree. Here, we investigate whether 10 years of experimental NO3− deposition (30 kg N ha−1 y−1) could induce NO3− uptake and assimilation in overstory sugar maple (approximately 90 years old), which would enable this species to function
as a direct sink for atmospheric NO3− deposition. Kinetic parameters for NH4+ and NO3− uptake in fine roots, as well as leaf and root NO3− reductase activity, were measured under conditions of ambient and experimental NO3− deposition in four sugar maple-dominated stands spanning the geographic distribution of northern hardwood forests in the
Upper Lake States. Chronic NO3− deposition did not alter the V
max or K
m for NO3− and NH4+ uptake nor did it influence NO3− reductase activity in leaves and fine roots. Moreover, the mean V
max for NH4+ uptake (5.15 μmol 15N g−1 h−1) was eight times greater than the V
max for NO3− uptake (0.63 μmol 15N g−1 h−1), indicating a much greater physiological capacity for NH4+ uptake in this species. Additionally, NO3− reductase activity was lower than most values for woody plants previously reported in the literature, further indicating
a low physiological potential for NO3− assimilation in sugar maple. Our results demonstrate that chronic NO3− deposition has not induced the physiological capacity for NO3− uptake and assimilation by sugar maple, making this dominant species an unlikely direct sink for anthropogenic NO3− deposition. 相似文献
10.
Corynebacterium acetoacidophilum RYU3161 was cultivated in al-histidine-limited fed-batch culture. To investigate the effect of cell growth on thel-proline production, 5l fed-batch culture was performed using an exponential feeding rate to obtain the specific growth rates (μ) of 0.04, 0.06,
0.08, and 0.1 h−1. The results show that the highest production ofl-proline was obtained at μ=0.04 h−1. The specificl-proline production rate (Qp) increased proportionally as a function of the specific growth rate, but decreased after it revealed the maximum value at
μ=0.08 h−1. Thus, the highest productivity ofl-proline was 1.66 g L−1 h−1 at μ=0.08 h−1. The results show that the production of L-proline inC. acetoacidophilum RYU3161 has mixed growth-associated characteristics. 相似文献
11.
The effects of glycerol and the oxygen transfer rate on the xylitol production rate by a xylitol dehydrogenase gene (XYL2)-disrupted mutant of Candida tropicalis were investigated. The mutant produced xylitol near the almost yield of 100% from d-xylose using glycerol as a co-substrate for cell growth and NADPH regeneration: 50 g d-xylose l−1 was completely converted into xylitol when at least 20 g glycerol l−1 was used as a co-substrate. The xylitol production rate increased with the O2 transfer rate until saturation and it was not necessary to control the dissolved O2 tension precisely. Under the optimum conditions, the volumetric productivity and xylitol yield were 3.2 g l−1 h−1 and 97% (w/w), respectively. 相似文献
12.
The differences in pigment levels, photosynthetic activity and the chlorophyll fluorescence decrease ratio R
Fd (as indicator of photosynthetic rates) of green sun and shade leaves of three broadleaf trees (Platanus acerifolia Willd., Populus alba L., Tilia cordata Mill.) were compared. Sun leaves were characterized by higher levels of total chlorophylls a + b and total carotenoids x + c as well as higher values for the weight ratio chlorophyll (Chl) a/b (sun leaves 3.23–3.45; shade leaves: 2.74–2.81), and lower values for the ratio chlorophylls to carotenoids (a + b)/(x + c) (with 4.44–4.70 in sun leaves and 5.04–5.72 in shade leaves). Sun leaves exhibited higher photosynthetic rates P
N on a leaf area basis (mean of 9.1–10.1 μmol CO2 m−2 s−1) and Chl basis, which correlated well with the higher values of stomatal conductance G
s (range 105–180 mmol m−2 s−1), as compared to shade leaves (G
s range 25–77 mmol m−2 s−1; P
N: 3.2–3.7 μmol CO2 m−2 s−1). The higher photosynthetic rates could also be detected via imaging the Chl fluorescence decrease ratio R
Fd, which possessed higher values in sun leaves (2.8–3.0) as compared to shade leaves (1.4–1.8). In addition, via R
Fd images it was shown that the photosynthetic activity of the leaves of all trees exhibits a large heterogeneity across the
leaf area, and in general to a higher extent in sun leaves than in shade leaves. 相似文献
13.
Kaarel Adamberg Petri-Jaan Lahtvee Kaspar Valgepea Kristo Abner Raivo Vilu 《Antonie van Leeuwenhoek》2009,95(3):219-226
Quasi steady state growth of Lactococcus
lactis IL 1403 was studied in glucose-limited A-stat cultivation experiments with acceleration rates (a) from 0.003 to 0.06 h−2 after initial stabilization of the cultures in chemostat at D = 0.2–0.3 h−1. It was shown that the high limit of quasi steady state growth rate depended on the acceleration rate used—at an acceleration
rate 0.003 h−2 the quasi steady state growth was observed until μ
crit = 0.59 h−1, which is also the μ
max value for the culture. Lower values of μ
crit were observed at higher acceleration rates. The steady state growth of bacteria stabilized at dilution rate 0.2 h−1 was immediately disrupted after initiating acceleration at the highest acceleration rate studied—0.06 h−2. Observation was made that differences [Δ(μ − D)] of the specific growth rates from pre-programmed dilution rates were the lowest using an acceleration rate of 0.003 h−2 (< 4% of preset changing growth rate). The adaptability of cells to follow preprogrammed growth rate was found to decrease
with increasing dilution rate—it was shown that lower acceleration rates should be applied at higher growth rates to maintain
the culture in the quasi steady state. The critical specific growth rate and the biomass yields based on glucose consumption
were higher if the medium contained S
0 = 5 g L−1 glucose instead of S
0 = 10 g L−1. It was assumed that this was due to the inhibitory effect of lactate accumulating at higher concentrations in the latter
cultures. Parallel A-stat experiments at the same acceleration and dilution rates showed good reproducibility—Δ(μ − D) was less than 5%, standard deviations of biomass yields per ATP produced (Y
ATP), and biomass yields per glucose consumed (Y
XS) were less than 15%. 相似文献
14.
The biokinetics of glucose metabolism were evaluated in Aeromonas hydrophila during growth in an anaerobic biosystem. After approx 34 h growth, A. hydrophila metabolized 5,000 mg glucose l−1 into the end-products ethanol, acetate, succinate and formate. The maximum growth rate, μ
m, half saturation coefficients, K
s, microbial yield coefficient, Y, cell mass decay rate coefficient, k
d, and substrate inhibition coefficient, K
si were 0.25 ± 0.03 h−1, 118 ± 31 mg glucose l−1, 0.12 μg DNA mg glucose−1, 0.01 h−1, and 3,108 ± 1,152 mg glucose l−1, respectively. These data were used to predict the performance of a continuous growth system with an influent glucose concentration
of 5,000 mg l−1. Results of the analysis suggest that A. hydrophila will metabolize glucose at greater than 95% efficiency when hydraulic retention times (HRTs) exceed 7 h, whereas the culture
is at risk of washing out at an HRT of 6.7 h. 相似文献
15.
Decolourization of anaerobically digested and polyaluminium chloride treated distillery spentwash was studied in a fungal
stirred tank aerobic reactor without dilution of wastewater. Aspergillus niger isolate IITB-V8 was used as the fungal inoculum. The main objectives of the study were to optimize the stirrer speed for
achieving maximum decolourization and to determine the kinetic parameters. A mathematical model was developed to describe
the batch culture kinetics. Volumetric oxygen transfer coefficient (k
L
a) was obtained using dynamic method. The maximum specific growth rate and growth yield of fungus were determined using Logistic
equation and using Luedeking–Piret equation. 150 rpm was found to be optimum stirrer speed for overall decolourization of
87%. At the optimum stirrer speed, volumetric oxygen transfer coefficient (k
L
a) was 0.4957 min−1 and the maximum specific growth rate of fungus was 0.224 h−1. The values of yield coefficient (Y
x/s) and maintenance coefficient (m
s) were found to be 0.48 g cells (g substrate)−1 and 0.015 g substrate (g cells)−1 h−1. 相似文献
16.
Daniela de Araújo Viana Marques Beatriz Rivas Torres Ana Lúcia Figueiredo Porto Adalberto Pessoa-Júnior Attilio Converti 《Biochemical Engineering Journal》2009,47(1-3):122-126
Aeration and agitation are important variables to ensure effective oxygen transfer rate during aerobic bioprocesses; therefore, the knowledge of the volumetric mass transfer coefficient (kLa) is required. In view of selecting the optimum oxygen requirements for extractive fermentation in aqueous two-phase system (ATPS), the kLa values in a typical ATPS medium were compared in this work with those in distilled water and in a simple fermentation medium, in the absence of biomass. Aeration and agitation were selected as the independent variables using a 22 full factorial design. Both variables showed statistically significant effects on kLa, and the highest values of this parameter in both media for simple fermentation (241 s−1) and extractive fermentation with ATPS (70.3 s−1) were observed at the highest levels of aeration (5 vvm) and agitation (1200 rpm). The kLa values were then used to establish mathematical correlations of this response as a function of the process variables. The exponents of the power number (N3D2) and superficial gas velocity (Vs) determined in distilled water (α = 0.39 and β = 0.47, respectively) were in reasonable agreement with the ones reported in the literature for several aqueous systems and close to those determined for a simple fermentation medium (α = 0.38 and β = 0.41). On the other hand, as expected by the increased viscosity in the presence of polyethylene glycol, their values were remarkably higher in a typical medium for extractive fermentation (α = 0.50 and β = 1.0). A reasonable agreement was found between the experimental data of kLa for the three selected systems and the values predicted by the theoretical models, under a wide range of operational conditions. 相似文献
17.
Scott GR Keir KR Schulte PM 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2005,175(7):499-510
We have explored the possible mechanisms by which mineralocorticoid (MR) and glucocorticoid (GR) receptors regulate the response
to freshwater transfer in the gills of the euryhaline killifish Fundulus heteroclitus. Killifish were implanted with RU486 (GR antagonist) or spironolactone (MR antagonist) at doses of 0.1–1.0 mg g−1, and subsequently transferred from 10‰ brackish water to freshwater. Compared to brackish water sham fish, mRNA expression
of CFTR and NKCC1 decreased in the gills of sham fish transferred to freshwater, whereas Na+,K+–ATPase α1a
mRNA expression and α protein abundance, as well as cell proliferation (detected using BrdU) increased. Spironolactone inhibited
the normal increase in cell proliferation and Na+,K+-ATPase expression after freshwater transfer. RU486 increased plasma cortisol levels and may have slightly inhibited Na+,K+–ATPase activity, but did not change α 1a
expression. RU486 had no effect on cell proliferation in the non-lamellar region of the gills, but increased proliferation
in the lamellar region. Neither antagonist inhibited the suppression of CFTR or NKCC1 expression after freshwater transfer.
Glucocorticoid receptor expression was reduced in all sham and antagonist treatments compared to untreated controls, but no
other consistent differences were observed. The effects of spironolactone suggest that MR is important for regulating ion
transport in killifish gills after freshwater transfer. 相似文献
18.
Liu Y Sha Q Wu S Wang J Yang L Sun W 《Journal of industrial microbiology & biotechnology》2006,33(4):274-282
A microorganism with the ability to catalyze the resolution of racemic phenyloxirane was isolated and identified as Aspergillus niger SQ-6. Chiral capillary electrophoresis was successfully applied to separate both phenyloxirane and phenylethanediol. The
epoxide hydrolase (EH) involved in this resolution process was (R)-stereospecific and constitutively expressed. When whole cells were used during the biotransformation process, the optimum
temperature and pH for stereospecific vicinal diol production were 35°C and 7.0, respectively. After a 24-h conversion, the
enantiomer excess of (R)-phenylethanediol produced was found to be >99%, with a conversion rate of 56%. In fed-batch fermentations at 30°C for 44 h,
glycerol (20 g L−1) and corn steep liquor (CSL) (30 g L−1) were chosen as the best initial carbon and nitrogen sources, and EH production was markedly improved by pulsed feeding of
sucrose (2 g L−1 h−1) and continuous feeding of CSL (1 g L−1 h−1) at a fermentation time of 28 h. After optimization, the maximum dry cell weight achieved was 24.5±0.8 g L−1; maximum EH production was 351.2±13.1 U L−1 with a specific activity of 14.3±0.5 U g−1. Partially purified EH exhibited a temperature optimum at 37°C and pH optimum at 7.5 in 0.1 M phosphate buffer. This study
presents the first evidence for the existence of a predicted epoxide racemase, which might be important in the synthesis of
epoxide intermediates. 相似文献
19.
Collopy-Junior I Kneipp LF da Silva FC Rodrigues ML Alviano CS Meyer-Fernandes JR 《Archives of microbiology》2006,185(5):355-362
In this work, we characterized an ecto-ATPase activity in intact mycelial forms of Fonsecaea pedrosoi, the primary causative agent of chromoblastomycosis. In the presence of 1 mM EDTA, fungal cells hydrolyzed adenosine-5′-triphosphate (ATP) at a rate of 84.6 ± 11.3 nmol Pi h−1 mg−1 mycelial dry weight. The ecto-ATPase activity was increased at about five times (498.3 ± 27.6 nmol Pi h−1 mg−1) in the presence of 5 mM MgCl2, with values of V
max and apparent K
m for Mg-ATP2−corresponding to 541.9 ± 48.6 nmol Pi h−1 mg−1 cellular dry weight and 1.9 ± 0.2 mM, respectively. The Mg2+-stimulated ecto-ATPase activity was insensitive to inhibitors of intracellular ATPases such as vanadate (P-ATPases), bafilomycin A1 (V-ATPases), and oligomycin (F-ATPases). Inhibitors of acid phosphatases (molybdate, vanadate, and fluoride) or alkaline phosphatases (levamizole) had no effect on the ecto-ATPase activity. The surface of the Mg2+-stimulated ATPase in F. pedrosoi was confirmed by assays in which 4,4′-diisothiocyanostylbene-2,2′-disulfonic acid (DIDS), a membrane impermeant inhibitor, and suramin, an inhibitor of ecto-ATPase and antagonist of P2 purinoreceptors. Based on the differential expression of ecto-ATPases in the different morphological stages of F. pedrosoi, the putative role of this enzyme in fungal biology is discussed. 相似文献
20.
Abrunhosa L Costa M Areias F Venâncio A Proença F 《Journal of industrial microbiology & biotechnology》2007,34(12):787-792
The activity on Aspergillus spp. growth and on ochratoxin A production of two novel chromene dimers (3) was evaluated. The results of the bioassays indicate that the chromene dimer 3a inhibited mycelia growth by approximately 50% (EC50) at 140.1 μmol L−1 for A. niger, 384.2 μmol L−1 for A. carbonarius, 69.1 μmol L−1 for A. alliaceus and 559.1 μmol L−1 for A. ochraceus. When applied at concentrations of 2 mmol L−1, 3a totally inhibited the growth of all Aspergillus spp. tested. Furthermore, ochratoxin A production by A. alliaceus was reduced by about 94% with a 200 μmol L−1 solution of this compound. A moderate inhibitory effect was observed for the analogous structure 3b on ochratoxin A production but not in mycelia growth. No inhibition was registered for compounds 2a and 2b, used as synthetic precursors of the dimeric species 3. 相似文献