Evaluation of production and characterization of polygalacturonase by Aspergillus niger ATCC 9642

The aim of our study was to evaluate polygalacturonase (PG) production and characterization by Aspergillus niger ATCC 9642. The maximum PG activity (51.82 U/mL) was obtained using pectin, l-asparagine, and, iron sulphate concentrations of 32 g/L, 2 g/L, 0.06 g/L and 1.0 g/L, respectively; 180 rpm of stirring rate, 25 °C and an initial pH of 4.0. The kinetic study showed that the highest enzyme activity was achieved at 27 h of fermentation. The evaluation of the optimum pH and temperature permitted us to observe that highest PG activities were achieved at 37 °C and pH of 5.5. The enzymatic extract presented higher stability at 55 °C and pH of 5.0. The results showed that at low temperatures the enzyme extract kept the initial activity until 40 days of storage. The experimental design methodology permitted us to optimize the PG activity and an important aspect of this study is the characterization of the PG in terms of optimum temperature and pH using experimental design technique and also, the characterization of enzyme stability at low temperature. Such studies are very scarce in the literature and should be helpful to understand the true potentialities of pectinases in its industrial applications.     

The effect of pH on bioremediation potential for the removal of direct violet textile dye by Aspergillus niger

Alkaline and acidic media have been used in the textile dye industry, depending on the fabric nature. The bioremoval of textile direct violet dye by Aspergillus niger fungal strain was studied. The effect of pH on dye bioremoval was investigated at a pH range from 2 to 11. The direct violet dye bioremoval reached maximum with 92.4%, 64.0%, 91.4%, and 62.3 % at pH values of 2, 3, 8, and 9, respectively, at 24 h of incubation. The percentages of removal rate after 72 h incubation were 98.9, 97.3, 94.0, 95.0, 97.0, and 97.3 at pH 2, 3, 6, 7, 8, and 9, respectively. The optimum pH values were 2, 3, 8, and 9 for direct dye removal. At the end of the experiments, the treatment with fungal strain could reduce COD value of synthetic dye solution by 76-91%. Pseudo first and second order kinetic models were applied to evaluate differences in the biosorption rates and uptakes of textile dye. Pre-equilibrium biosorption of direct violet dye onto fungus under different dye concentrations followed a pseudo second order kinetic model with a high degree of correlation coefficients (R² > 0.99), and the calculated values of q_e nearly matched the experimental values of textile dye during the biotreatment process.     

Pulverized coal combustion and NOx emissions in high temperature air from circulating fluidized bed

A new technique of achieving high temperature air was adopted by combustion in high excess air ratio in a circulating fluidized bed (CFB). Experiments on pulverized coal combustion in high temperature air from the CFB were made in a down-fired combustor with the diameter of 220 mm and the height of 3000 mm. High temperature air with lower oxygen concentrations can be achieved steadily and continuously by combustion in the circulating fluidized bed. Pulverized coal combustion in high temperature air shows a uniform temperature profile along the axis of the down-fired combustor and the combustion efficiency is 99.8%. The NO_x emission is 390 mg/m³, 13% lower than the regulation for thermal power plants in China. The HCN and NH₃ emissions, as well as N₂O, are about zero in the exhaust.     

Rich bioactive phenolic extract production by microbial biotransformation of Brazilian Citrus residues

Flavanones in Citrus are molecules that play an important role in antioxidant activities in nutraceutical products. Recent studies indicate that molecules of the simplest classes of phenolics have higher biological activity and absorption capacity. However, the molecules that have been shown to be very important bioactive compounds of Citrus, such as hesperetin, naringenin and ellagic acid, are found in trace concentrations in the fruit. An interesting environmentally friendly alternative that deserves attention regarding phenolic compound obtaining is the biotransformation of these molecules. The aim of this study was to develop a process of biotransformation of phenolics from Brazilian Citrus residues by solid-state fermentation with the microorganism Paecilomyces variotii. The optimized fermentation conditions were 10 g of Citrus residues (2.0 mm of substrate particle size), 20 mL distilled water, at 32 °C after 48 h of incubation. The development of this process has generated, simultaneously, an increase of 900, 1400 and 1330% of hesperetin, naringenin and ellagic acid concentration, respectively, and an increase of 73% of the antioxidant capacity. These results give strong evidence that microbial biotransformation does not only produce phenolic compounds but also compounds with high biological activity, such as hesperetin and naringenin.     

Low temperature air oxidation of n-alkanes in the presence of Na-smectite

This paper is the continuation of a study concerning the catalytic effects of clay on organic matter and especially n-alkanes during oxidation carried out at low temperature. The influences of clay minerals were investigated to understand their role better during natural oxidation of organic matter.n-Alkanes oxidation experiments in presence of Na-smectite were carried out at 100 °C during 512 h and reveal an important production of oxygen-bearing molecules to the detriment of initial n-alkanes. Thus, Na-smectite allows to initiate the auto-oxidation of n-alkanes due to its chemical (charged sheets) and/or physical (high specific area) properties. The evolution of oxygen-bearing molecules distribution enables to distinguish two competitive chemical pathways. On one hand, alcohols and ketones are produced with an aliphatic chain length similar to the starting n-alkanes. On the other hand, aliphatic chain cleavages occur and principally produce 1-alcohols, 2-ketones, carboxylic acids and 3-substitued γ-lactones. These oxygen-bearing compounds are more and more preponderant and evidence the fact that cleavage mechanisms become progressively dominant.     

Generation and relaxation of large stress in the photoinduced solid-state polymerization reaction of diethyl muconate detected by simultaneous time-resolved measurement of X-ray diffraction and Raman spectra

Simultaneous measurement of X-ray diffraction and Raman spectra has been performed for studying the structural changes in the photoinduced solid-state polymerization reaction of diethyl Z,Z-muconate (EMU) single crystal. As the reaction proceeded, the X-ray reflections coming from the polymer species started to appear and shifted the positions toward those of the finally attained polymer product. The Raman bands of the polymer species were also found to shift their frequencies toward those of the final polymer. From these experimental data, combined with the previously reported information on crystal structure and Raman shift data collected for stressed polymer single crystal, it was deduced reasonably that the polymer chains generated in the initial stage of reaction were strongly stressed because of the geometrical constraints coming from the surrounding monomer matrix and that the stress was gradually relaxed as the reaction proceeded.     

Successful Treatment of Liver Aspergilloma by Caspofungin Acetate First-Line Therapy in a Non-Immunocompromised Patient

Aspergillosis remains to be a life-threatening complication in immunocompromised patients. However, Aspergillus infection can be observed in non-immunocompromised individuals in rare cases. We report a case of liver aspergilloma in a chronic aplastic anemia patient under relatively intact immune status. Therapeutic strategy for this rare condition was extensively discussed and caspofungin acetate single agent first-line therapy was applied after careful consideration. Encouraging clinical and radiologic improvements were achieved in response to the antifungal salvage. Our long-term follow-up study also revealed a favorable prognosis. Based on this experience, we suggest caspofungin acetate as first-line therapy for treatment plans of liver aspergilloma.     

Assessment of Aspergillus fumigatus in Guinea Pig Bronchoalveolar Lavages and Pulmonary Tissue by Culture and Realtime Polymerase Chain Reaction Studies

In this study we pursued a diagnostic target in Aspergillus fumigatus (AF) by using qualitative Realtime PCR combined with proprietary DNA primers and a hydrolysis probe specific for this fungal target. Qualitative Realtime PCR is a diagnostic tool that utilizes Realtime PCR technology and detects the presence or absence target specific DNA within a predetermined detection range. Respiratory tissue and fluids from experimentally infected guinea pigs were tested by extracting DNA from the samples which were amplified and detected using AF specific DNA primers and probe. This study included qualitative evaluations of all specimens for the presence of the DNA of AF. The findings in the tissues after AF infection were compared to the numbers of spores in aerosolized samples used to inoculate the animals. Results demonstrated that the specific probe and primer set could detect the presence or absence of AF DNA in the sample. The qualitative detection limit of the assay ranged from 6 × 10(4) copies to 6 copies. Since blood cultures are rarely positive for Aspergillosis, our data indicate that qualitative Realtime PCR, in combination with the appropriate DNA primers and probe can serve as an effective diagnostic tool in the early detection of fungal infections.     

Electrochemical characterizations of Fe-substituted LiNiO2 synthesized in air by the combustion method

The phases that appear in the intermediate reaction steps for the formation of lithium nickel oxide were deduced from XRD and DTA analyses. XRD analysis and electrochemical measurements were performed for LiNi_1−yFe_yO₂ (0.000 ≤ y ≤ 0.300) samples calcined in air after preheating in air at 400 °C for 30 min. Rietveld refinement of the LiNi_1−yFe_yO₂ XRD patterns (0.000 < y ≤ 0.100) was carried out from a [Li,Ni]_3b[Li,Ni,Fe]_3a[O₂]_6c starting structure model. The samples of LiNi_1−yFe_yO₂ with y = 0.025 and 0.050 had higher first discharge capacities when compared with LiNiO₂ and exhibited better or similar cycling performance at a 0.1 C rate in the voltage range of 2.7–4.2 V. The LiNi_0.975Fe_0.025O₂ sample had the highest first discharge capacity of 176.5 mAh/g and a discharge capacity of 121.0 mAh/g at n = 100. With the exception of Co-substituted LiNiO₂, such a high first discharge capacity has not been previously reported.     

Thermally- and solvent-induced crystallization kinetics of syndiotactic polystyrene viewed from time-resolved measurements of infrared spectra at the various temperatures (1) estimation of glass transition temperature shifted by solvent absorption

syndiotactic Polystyrene (sPS) glass crystallizes into the α form when it is heated above the glass transition temperature (T_g, about 100 °C). sPS can be crystallized also into the δ form in the solvent atmosphere at room temperature. In order to trace the structural evolution process, the time-resolved infrared spectral measurements have been performed in the isothermal crystallization from the glass to α form and in the solvent-induced crystallization from the glass to δ form at the various temperatures. Absorbance of crystallization-sensitive infrared bands was plotted against time, from which the crystallization kinetics were analyzed on the basis of Avrami equation: X(t)=1−exp[−(kt)ⁿ] where X is a normalized crystallinity, n is an index, k is a rate constant, and t is a time. The isothermal crystallization was investigated also by carrying out the temperature jump experiment of DSC thermograms, giving almost the same results as the infrared spectral measurements. The Avrami index n was 2-5 depending on the crystallization temperature (T_c). The k was also dependent on the T_c, about 10⁻¹-10⁻⁴ s⁻¹ and could be fitted reasonably by the equation of crystallization kinetics. An extrapolation of the k vs T_c plot to the negligibly small k value allowed us to predict the temperature at which no crystallization should occur, ca. 100 °C, in good agreement with the observed T_g value. On the other hand, the solvent-induced crystallization was investigated for the first time at the various temperatures from 50 to 9 °C by the time-resolved measurement of infrared spectra. Compared with the experiment at room temperature, the crystallization was highly accelerated at 40-50 °C, while the crystallization rate was reduced remarkably at such a low temperature as 9 °C. The time dependence of infrared absorbance was analyzed for the crystallization-sensitive bands on the basis of Avrami equation as the first approximation, although the crystallization mechanism was more complicated than the isothermal crystallization case. The logarithm of the k value was found to change almost linearly with temperature and an extrapolation to infinitesimally small k value gave a T_g of about −15 °C. That is to say, the glass transition temperature was estimated to shift remarkably from 100 to −15 °C by absorbing solvent molecules or by a plasticizing effect.     

Optimization of citric acid production by <Emphasis Type="Italic">Aspergillus niger</Emphasis> NRRL 567 grown in a column bioreactor

Citric acid production using Aspergillus niger NRRL 567 grown on peat moss has been optimized in a column bioreactor using a statistically based method. A 23 full factorial design with eight fermentation conditions was applied to evaluate significance on citric acid production and their interactions between variables, where the three independent variables evaluated were aeration rate, bed depth and temperature. Aeration rate and fermentation temperature were identified to be significant variables. Citric acid production markedly increases with aeration rate and fermentation temperature; however, the bed depth of solid substrate showed an insignificant effect on citric acid production. The optimum fermentation condition for citric acid production in a column bioreactor consisted of aeration rate of 0.84 vvm, bed depth of 22 cm and fermentation temperature of 32 °C. Under a given condition, a maximum citric acid production of 120.6 g/l was predicted and matched well with the experimental value of 123.9 g/kg.     

Control of plant-parasitic nematodes by a nematicidal strain ofAspergillus niger

An isolate ofAspergillus niger (designated PD-42) was evaluated in laboratory, greenhouse, and field trials for efficacy in controlling plant-parasitic nematodes. In greenhouse experiments, PD-42 drenches containing spores of PD-42 on oatmeal significantly reduced galling on tomato due to root-knot nematode as compared to untreated controls. In a one-half acre field experiment, PD-42 incorporated in seed coats was associated with significantly increased yield and decreased root-knot galling on pepper. In a second one-half acre field experiment, PD-42 drenches significantly reduced tomato and pepper root galling due toMeloidogyne incognita, and nonsignificant yield increases occurred. In each field experiment, treatment with PD-42 reducedRotylenchulus reniformis populations. The nematicidal components of theA. niger culture filtrates include citric acid, oxalic acid, and undetermined molecules larger than 8000 MW.     

Short-wavelength light beam in situ monitoring growth of InGaN/GaN green LEDs by MOCVD

In this paper, five-period InGaN/GaN multiple quantum well green light-emitting diodes (LEDs) were grown by metal organic chemical vapor deposition with 405-nm light beam in situ monitoring system. Based on the signal of 405-nm in situ monitoring system, the related information of growth rate, indium composition and interfacial quality of each InGaN/GaN QW were obtained, and thus, the growth conditions and structural parameters were optimized to grow high-quality InGaN/GaN green LED structure. Finally, a green LED with a wavelength of 509 nm was fabricated under the optimal parameters, which was also proved by ex situ characterization such as high-resolution X-ray diffraction, photoluminescence, and electroluminescence. The results demonstrated that short-wavelength in situ monitoring system was a quick and non-destroyed tool to provide the growth information on InGaN/GaN, which would accelerate the research and development of GaN-based green LEDs.     

Use of surface response methodology to optimize culture conditions for iturin A production by Bacillus subtilis in solid-state fermentation

Response surface methodology (RSM) was employed to optimize the cultivation conditions of Bacillus subtilis S3 for the enhancement of iturin A, a lipopeptide antibiotic used as biological pesticide, production in solid-state fermentation (SSF). The statistic experimental model predicted a maximum iturin production of 11.435 mg/g-wet solid material. Verification of the calculated maximum was done with experiments that were performed in the culture media representing the optimum combination found, and the iturin A production of 11.447 mg/g-wet solid material (average of three repeats) was obtained when B. subtilis S3 was cultivated at 25 °C for 5 days in solid fermentation containing high gluten flour 10 g and rice bran 50 g in addition to glucose 1.15%, KH₂PO₄ 1.27 mM, MgSO₄ 5.08 mM, peanut oil 1.01%, inoculum 19.49% and water content 44.97%. The iturin A production by B. subtilis S3 was increased significantly by 23%, from 9.26 mg/g-wet solid material to 11.447 mg/g-wet solid material when the strain was cultivated in the optimal medium developed by surface response methodology, as compared to medium conventionally developed by one-factor-at-a-time. The yield of iturin A (11.447 mg/g-wet solid material, with 45% moisture content) produced by B. subtilis S3 reported in this study is the highest reported to date for B. subtilis species in SSF. In addition, the use of rice bran as a substrate in solid-state fermentation for iturin A production by B. subtilis is unique.     

Assessment of a redox alkaline/iron-chelate absorption process for the removal of dilute hydrogen sulfide in air emissions

The oxidative absorption of hydrogen sulfide (H₂S) into a solution of ferric chelate of trans-1,2- diaminocyclohexanetetraacetate (CDTA) was studied in a counter-current laboratory column randomly packed with 15 mm plastic Ralu rings. The present investigation takes concern about the Kraft pulping situation where dilute H₂S concentrations are omnipresent in large-volume gas effluents. A fractional two-level factorial approach was instigated to determine the significance of six operating variables, namely the solution's alkalinity (pH; 8.5-10.5), the liquid mass flow rate (L;1.73-), the solution's ionic strength (I_C;0.01-), the gas mass flow rate (G;0.19-), the inlet H₂S concentration (C_H2S,0;70-430 ppm) and the initial ferric CDTA concentration (C_Fe,0;100 -). Initially, a Plackett-Burman design matrix of seven duplicated experiments revealed that pH is the leading factor controlling the H₂S conversion rate while the ionic strength and ferric CDTA concentration effects remained negligible within the factorial domain. Surface response analysis based on 11 duplicated factorial experiments plus 10 central composite trials revealed that the H₂S conversion significantly increases with liquid flow rate but decreases with growing H₂S load up. Further examination about the influence of ferric CDTA on H₂S absorption rate was set up over a broader concentration range (C_Fe,0;0- at pH of 9.5 and 10.5. It showed good potential at as H₂S conversion increased by a significant 25% for both pH values in comparison to pure alkaline solutions containing no ferric CDTA.