The Influence of Initial Xylose Concentration, Agitation, and Aeration on Ethanol Production by Pichia stipitis from Rice Straw Hemicellulosic Hydrolysate

Rice straw hemicellulosic hydrolysate was used as fermentation medium for ethanol production by Pichia stipitis NRRL Y-7124. Shaking bath experiments were initially performed aiming to establish the best initial xylose concentration to be used in this bioconversion process. In the sequence, assays were carried out under different agitation (100 to 200 rpm) and aeration (V _flask/V _medium ratio varying from 2.5 to 5.0) conditions, and the influence of these variables on the fermentative parameters values (ethanol yield factor, Y _P/S; cell yield factor, Y _X/S; and ethanol volumetric productivity, Q _P) was investigated through a 2² full-factorial design. Initial xylose concentration of about 50 g/l was the most suitable for the development of this process, since the yeast was able to convert substrate in product with high efficiency. The factorial design assays showed a strong influence of both process variables in all the evaluated responses. The agitation and aeration increase caused a deviation in the yeast metabolism from ethanol to biomass production. The best results (Y _P/S?= 0.37 g/g and Q _P?=?0.39 g/l.h) were found when the lowest aeration (2.5 V _flask/V _medium ratio) and highest agitation (200 rpm) levels were employed. Under this condition, a process efficiency of 72.5% was achieved. These results demonstrated that the establishment of adequate conditions of aeration is of great relevance to improve the ethanol production from xylose by Pichia stipitis, using rice straw hemicellulosic hydrolysate as fermentation medium.     

Selection of a Thermotolerant Kluyveromyces marxianus Strain with Potential Application for Cellulosic Ethanol Production by Simultaneous Saccharification and Fermentation

The development of technologies for cellulosic ethanol production by simultaneous saccharification and fermentation (SSF) depends on the use of microorganisms with high fermentative rates and thermotolerance. In this study, the ability of five Kluyveromyces marxianus strains to produce ethanol from glucose at 45 °C was investigated. The highest fermentative parameters were observed with K. marxianus NRRL Y-6860, which was then further studied. An initial evaluation of the oxygen supply on ethanol production by the selected yeast and a comparison of SSF process from acid pretreated rice straw between K. marxianus NRRL Y-6860 and Saccharomyces cerevisiae at 30 and 45 °C were carried out. Under the lowest evaluated conditions of aeration and agitation, K. marxianus NRRL Y-6860 produced 21.5 g/L ethanol from 51.3 g/L glucose corresponding to Y_P/S of 0.44 g/g and Q_P of 3.63 g/L h. In the SSF experiments, K. marxianus NRRL Y-6860 was more efficient than S. cerevisiae at both evaluated temperatures (30 and 45 °C), attained at the highest temperature an ethanol yield of 0.24 g/g and productivity of 1.44 g/L h.     

Effect of process parameters on production of a biopolymer by Rhizobium sp.

The production of biopolymers by a Rhizobium strain was studied under batch and bioreactor conditions. The best viscosity levels were obtained under low mannitol concentrations as well as low agitation and aeration conditions. Infrared spectra indicated the presence of chemical groups characteristic of microbially produced biopolymers, including C=O and O-acetyl groups. Thermogravimetric analysis showed the characteristic degradation profiles of the exopolysaccharide produced (T _onset=290°C). The experimental design showed that a low substrate concentration (10.0 g/L), and low aeration (0.2 vvm) and agitation (200 rpm) levels should be used. The maximum yield of the process was a Yp/s (g/g) of 0.19±0.1, obtained under optimized conditions.     

A Study of the Effects of Aeration and Agitation on the Properties and Production of Xanthan Gum from Crude Glycerin Derived from Biodiesel Using the Response Surface Methodology

The effects of aeration and agitation on the properties and production of xanthan gum from crude glycerin biodiesel (CGB) by Xanthomonas campestris mangiferaeindicae 2103 were investigated and optimized using a response surface methodology. The xanthan gum was produced from CGB in a bioreactor at 28 °C for 120 h. Optimization procedures indicated that 0.97 vvm at 497.76 rpm resulted in a xanthan gum production of 5.59 g L^?1 and 1.05 vvm at 484.75 rpm maximized the biomass to 3.26 g L^?1. Moreover, the combination of 1.05 vvm at 499.40 rpm maximized the viscosity of xanthan at 0.5 % (m/v), 25 °C, and 25 s^?1 (255.40 mPa s). The other responses did not generate predictive models. Low agitation contributed to the increase of xanthan gum production, biomass, viscosity, molecular mass, and the pyruvic acid concentration. Increases in the agitation contributed to the formation of xanthan gum with high mannose concentration. Decreases in the aeration contributed to the xanthan gum production and the formation of biopolymer with high mannose and glucose concentrations. Increases in aeration contributed to increased biomass, viscosity, and formation of xanthan gum with greater resistance to thermal degradation. Overall, aeration and agitation of CGB fermentation significantly influenced the production of xanthan gum and its properties.     

Two-Staged Temperature and Agitation Strategy for the Production of Transglutaminase from a Streptomyces sp. Isolated from Brazilian Soils

Transglutaminase catalyzes the cross-linking reaction between a glutamine residue and a free amine residue of proteins leading to the formation of protein aggregates. In this research, the effects of temperature, agitation, and aeration on the production of transglutaminase in a bench reactor by a newly isolated Streptomyces sp. from Brazilian soils were investigated using a factorial experimental design. The parameters evaluated influenced the enzyme production, and the data showed that the best conditions to enhance cell growth were different from those leading to enhanced transglutaminase production. Thus, a temperature and agitation shift strategy was adopted to increase transglutaminase productivity. The temperature and agitation were first set at 34 °C and 350 rpm, respectively, and after 24 h decreasing to 26 °C and 150 rpm until the end of fermentation. The transglutaminase activity obtained was 2.18 U/mL after 42 h of fermentation, which was twice than that obtained using a constant temperature and agitation fermentation strategy.     

The Online Morphology Control and Dynamic Studies on Improving Vitamin B<Subscript>12</Subscript> Production by <Emphasis Type="Italic">Pseudomonas denitrificans</Emphasis> with Online Capacitance and Specific Oxygen Consumption Rate

The relationship between the morphological character of Pseudomonas denitrificans and vitamin B₁₂ synthesis based on real-time capacitance measurement and online specific oxygen consumption rate (Q _O2) control was established for enhancing vitamin B₁₂ production. Results demonstrated that the threshold Q _O2 value lower than 2.0 mmol/gDCW/l would greatly stimulate the state transfer from the cell number growth phase to the cell elongation phase and promote rapid vitamin B₁₂ biosynthesis, while the vitamin B₁₂ biosynthesis rate could also be inhibited when the rate of cell’s length-to-width ratio (ratio-LW) was higher than 10:1. Furthermore, the optimal morphology controlling strategy was achieved based on online Q _O2 control, which increases the appropriate active cell numbers at the former phase, and then control the elongation of ratio-LW no more than 10:1 at the vitamin B₁₂ biosynthesis phase. The maximal vitamin B₁₂ production reached 239.7 mg/l at 168 h, which was improved by 14.7 % compared with the control (208 mg/l). This online controlling strategy would be effectively applied for improving industrial vitamin B₁₂ fermentation.     

The Influence of Different Strategies for the Saccharification of the Banana Plant Pseudostem and the Detoxification of Concentrated Broth on Bioethanol Production

Pseudostem of the Musa cavendishii banana plant was submitted to chemical pretreatments with acid (H₂SO₄ 2%, 120 °C, 15 min) and with alkali (NaOH 3%, 120 °C, 15 min), saccharified by commercial enzymes Novozymes® (Cellic CTec2 and HTec2). The influences of the pretreatments on the degradation of the lignin, cellulose and hemicellulose, porosity of the surface, particle crystallinity, and yield in reducing sugars after saccharification (Y _RS), were established. Different concentrations of biomass (70 and 100 g/L in dry matter (dm)), with different physical differences (dry granulated, crushed wet bagasse, and whole pseudostem), were used. The broth with the highest Y _RS among the different strategies tested was evaporated until the concentration of reducing sugars (RS) was to the order of 100 g/L and fermented, with and without prior detoxification with active carbon. Fermentation was carried out in Erlenmeyer flasks, at 30 °C, initial pH 5.0, and 120 rpm. In comparison to the biomass without chemical pretreatment and to the biomass pretreated with NaOH, the acid pretreatment of 70 g/L of dry granulated biomass enabled greater digestion of hemicellulose, lower index of cellulose crystallinity, and higher Y _RS (45.8 ± 0.7%). The RS increase in fermentation broth to 100 g/L, with posterior detoxification, presented higher productivity ethanol (Q _P = 1.44 ± 0.02 g/L/h) with ethanol yield (Y _P/RS) of 0.41 ± 0.02 g/g. The value of Q _P was to the order of 75% higher than Q _P obtained with the same broth without prior detoxification.     

Polyethylene glycol-functionalized polyoctahedral silsesquioxanes as H+-conducting electrolytes

Proton-conducting electrolytes composed of a mixture of MePEG₇SO₃H acid and poly(ethylene) glycol-functionalized polyoctahedral silsesquioxanes (Q₈M₈-MePEG_n) are prepared. Eight MePEG_n (n?=?3, 7, and 12) arms are attached to a (HSiMe₂O)₈Si₈O₁₂ (Q₈M₈ ^H) core in the molecule. These Q₈M₈-MePEG_n compounds show nearly the same fractional free volume (FFV), but show increased volume fractions of PEG (V _f,PEG) and viscosities with longer PEG arms. At low MePEG₇SO₃H acid concentration (0.26 M), V _f,PEG and FFV dominantly affect the ionic conductivity. Q₈M₈-MePEG₁₂ shows the highest conductivity due to the largest V _f,PEG at 0.26 M. At a high acid concentration (1.32 M), the differences of V _f,PEG are much smaller and viscosity becomes more important. Q₈M₈-MePEG₃ reaches the largest conductivity of 1.32?×?10^?4 S cm^?1 at 55 °C at 1.32 M because of the lowest viscosity.     

Dopant depends on morphological and electrochemical characteristics of LiMn 2– X Mo X O4 cathode nanoparticles

For the first time, solid solutions of LiMn_2–X Mo _X O₄ nanoparticles were synthesized by combustion method at 700 °C in air. The synthesized LiMn_2–X Mo _X O₄ (X?=?0.0–0.2) nanoparticles were characterized by X-ray powder diffraction, Fourier transform infrared spectroscopy (FT-IR), Field emission-scanning electron microscopy, and Particle size analysis. The unit-cell constant is increasing from 8.237 to 8.293 Å with the increase of Mo, the presence of Mo at X?≤?0.05 in LiMn_2–X Mo _X O₄ nanoparticles retained the spinel structure (Fd-3m), whereas on increasing the Mo (X?≥?0.05 %), the ordering of Li⁺ ions in both octahedral and tetrahedral cationic position leads to the lowering of symmetry (P4₁32). On increasing the Mo content, prominent peak splitting and broadening are observed at 600–500 and 830 cm^?1 for Li–Mn–O and Mo–O respectively in the FT-IR spectra. The TG/DTA spectrum reveals that the convenient formation of Li mangano-molybdate is at 700 °C. The voltammograms of all the samples show two redox peaks centered around 4 V except for the sample with higher Mo doping (X?=?0.2). The sample with X?=?0.03 shows higher redox peak current values. A marginal increase of 146 Ω R _ct value was found for the LiMn_1.97Mo_0.03O₄ nanomaterial after 10th cycle which is rather high for the rest of the materials. A discharge capacity retention of 88 % at 50th cycle is observed for X?=?0.03 sample, while the other samples exhibit drastically reduced capacity. The LiMn_1.97Mo_0.03O₄ nanoparticle can able to deliver higher and constant discharge capacity, and it may be a good alternative for the existing cathode materials.     

Overproduction of riboflavin by anArthrobacter sp. mutant resistant to 5-fluorouracil

Effects of pH and dissolved oxygen concentration on batchwise riboflavin production by a 5-fluorouracil (5-FU)-resistant mutant ofArthrobacter sp. were investigated. The reaction was carried out in a jar fermentor. The optimal pH of culture medium was around 7.3. Dissolved oxygen concentration was almost constant during fermentation at 600 rpm of agitation rate. Production of riboflavin reached a maximum of 160 mg/L after 70 h fermentation under the agitation rate of 600 rpm, aeration rate of 1.0 L/min, and pH 7.0.     

Production of Mycophenolic Acid by <Emphasis Type="Italic">Penicillium brevicompactum</Emphasis> Using Solid State Fermentation

Solid-state fermentation using the microfungus Penicillium brevicompactum for the production of mycophenolic acid is reported in this paper. Of the initial substrates tested (whole wheat, cracked wheat, long grain Basmati rice, and short grain Parmal rice), Parmal rice proved to be the best. Under initial conditions, using steamed Parmal rice with 80% (w/w) initial moisture content, a maximum mycophenolic acid concentration of 3.4 g/kg substrate was achieved in 12 days of fermentation at 25 °C. The above substrate was supplemented with the following additional nutrients (g/L packed substrate): glucose 40.0, peptone 54.0, KH₂PO₄ 8.0, MgSO4?7H₂O 2.0, glycine 7.0, and methionine 1.65 (initial pH 5.0). A small amount of a specified trace element solution was also added. The final mycophenolic acid concentration was increased to nearly 4 g/kg substrate by replacing glucose with molasses. Replacing Parmal rice with rice bran as substrate further improved the mycophenolic acid production to nearly 4.5 g/kg substrate.     

Maximizing the xylitol production from sugar cane bagasse hydrolysate by controlling the aeration rate

Batch fermentations of sugar cane bagasse hemicellulosic hydrolysate treated for removing the inhibitors of the fermentation were performed byCandida guilliermondii FTI20037 for xylitol production. The fermentative parameters agitation and aeration rate were studied aiming the maximization of xylitol production from this agroindustrial residue. The maximal xylitol volumetric productivity (0.87 g/L h) and yield (0.67 g/g) were attained at 400/min and 0.45 v.v.m. (K_La 27/h). According to the results, a suitable control of the oxygen input permitting the xylitol formation from sugar cane bagasse hydrolysate is required for the development of an efficient fermentation process for large-scale applications.     

Revisiting structure of silica gels from water glass: an 1H and 29Si MAS and CP-MAS NMR study

The silica gels, derived from water glass solution with pH adjusted at 3.0 and 9.9, were revisited to investigate their constitution, although water glass has been studied for last tens of decades on gelation. Solid-state nuclear magnetic resonance spectroscopy was applied to the nuclei ¹H and ²⁹Si, by the use of magic angle spinning (MAS), ¹H → ²⁹Si CP-MAS (CP: cross-polarization), and modern techniques such as 2D HETCOR (two dimensional heteronuclear correlation), and variable-contact time CP techniques. Gelation time (t_gel) showed U-letter shape dependence on pH. All gels consisted of Qⁿ groups (n: 2, 3, and 4), where Qⁿ stands for a silicate unite [(O_1/2)_nSi (–O^?)_4?n] (n: 0–4). The analysis of the ¹H → ²⁹Si CP kinetics and ¹H-²⁹Si HETCOR spectra elucidated the presence of four kinds of ¹H nuclei, i.e., those giving a peak at 6.9 ppm in chemical shift δ: ¹H–OSi hydrogen bonded to H₂O molecules; one at 4.3 ppm: ¹H of adsorbed water molecules, hydrogen-bonded to the silanol groups; one at 1.7 ppm: ¹H–OSi confined in the gel lattice, including that forming aggregations like Si–O^H/_NaO–Si; and one at 4.2 ppm: ¹H of water molecules on the outermost hydration layer.     

Vibrational assignments of crystalline waters in some uranyl halide complexes

To establish the vibrational assignments of the bands near 450 and 320 cm⁻¹ in the hydrated uranyl halide complexes, M₂UO₂X₄·nH₂O (M = Na, K, Rb, Cs, NH₄; X = Cl, Br)m, their IR spectra have been measured in the region from 500 to 200 cm⁻¹ and investigated in some detail by making use of deuteration effect. The results show that the former band is evidently assigned to water libration (wagging vibration) and the latter to MO stretching vibration. Some possible structure of water coordination in the hydrated complexes is estimated on the basis of the spectral results.     

Investigation of hydrogen desorption from CaSiH by means of calorimetric method

The present work deals with the study of the reaction of hydrogen desorption from the CaSiH_X hydride by means of the calorimetric method. The dehydrogenation of the CaSiH_X hydride was carried out at 548 K. For a calorimetric study, the installation composed of the differential heat-conducting Tian–Calvet type calorimeter connected with a conventional Sieverts-type apparatus was employed. Such installation permitted us to obtain simultaneously the P-X isotherms (P—equilibrium hydrogen pressure, X = H/CaSi) and variation of the partial molar enthalpies of the reaction of hydrogen desorption from CaSiH_X with the hydrogen concentration in the metallic matrix. It was ascertained that in the CaSi-H₂ system there was one region where values of the partial molar enthalpy of the reaction of hydrogen desorption from the CaSiH_X hydride remained constant. This means that formation of one hydride phase in the CaSi-H₂ system took place. The enthalpy and entropy values for the reaction of hydrogen desorption from the CaSiH_X in the plateau range are ΔH _des = 53.8 ± 1.2 kJ mol^?1 H₂ and ΔS _des = 94.2 ± 2.7 J mol^?1 H₂ K^?1 (ΔH _des and ΔS _des—the differential molar enthalpy and entropy desorption, respectively).     

Copper Crystallization from Aqueous Solution: Initiation and Evolution of the Polynuclear Clusters

The initial steps of copper electrocrystallization process from aqueous solutions have been studied at DFT level of theory. It has been shown that Cu(H₂O) unit is the final product of Cu²⁺-ions electroreduction. From this particle clusters Cu_n·aq are formed and grow. Aggregation of copper atoms to the Cu_n·aq clusters consists of two steps. The first step includes condensation of Cu(H₂O) units to hydrated clusters Cu_n(H₂O)_n (n = 2–6). At the second step bonding of Cu(H₂O) particles is accompanied by dehydration of clusters yielding Cu_n(H₂O)_m structures (n > m). Cluster Cu₇·aq has been singled out as key structure based on calculated values of energies and Cu–Cu bond distances of Cu_n·aq clusters. This cluster is of D_5h symmetry which is typical for copper microcrystals formed from aqueous solutions in electrocrystallization processes on foreign surface. This key particle could be considered as a critical nucleus. Number of copper atoms therein matches average dimension of critical nucleus.     

Optimization of Oil-in-Water Emulsion Stability: Experimental Design,Multiple Light Scattering,and Acoustic Attenuation Spectroscopy

To find an optimal formulation of oil-in-water (O/W) emulsions (φ_o = 0.05), the effect of emulsifier nature and concentration, agitation speed, emulsifying time, storage temperature and their mutual interactions on the properties and behavior of these dispersions is evaluated by means of an experimental design (Nemrodw software). Long-term emulsion stability is monitored by multiple light scattering (Turbiscan ags) and acoustic attenuation spectroscopy (Ultrasizer). After matching surfactant HLB and oil required HLB, a model giving the Sauter diameter as a function of emulsifier concentration, agitation speed and emulsification time is proposed. The highest stability of C₁₂E₄-stabilized O/W emulsions is observed with 1% emulsifier.     

Production of xylitol byCandida mogii from rice straw hydrolysate

The influence of aeration level, initial pH, initial cell concentration, and fermentation time on the xylitol production from rice straw hemicellulose hydrolysate byCandida mogii was studied. A multifactorial experimental design was adopted to evaluate this influence. A statistical analysis of the results showed that the aeration level and the initial pH had significant effects on yield factor, volumetric productivity, and xylose consumption. For the latter, fermentation time was also a significant variable. Based on the response surface methodology, models for the range investigated were proposed. The maximum values for the yield factor (Y_p/s) and volumetric productivity (Q_p) were, respectively, 0.71 g/g and 0.46 g(Lh).     

Estimation of enzymatic,microbial, and chemical properties in Brown soil by microcalorimetry

The study was conducted with the objective to assess soil enzymatic, microbial, and chemical properties by customary methods and results obtained by conventional methods, corroborated with microcalorimetry. The experiment was laid out in a randomized complete block design with ten treatments in triplicates. The RS and GM were used at three rates (0, 5, and 25 mg g^?1 soil, respectively). The soils were maintained at two water levels 25 % (W1) and 200 % (W2) of soil water-holding capacity. All soil enzymatic, microbial, and chemical properties were measured by standard methods. The incorporation of GM and RS, especially at high rates and water levels, 25 % (W1) and 200 % (W2) significantly (p < 0.05) affected the soil enzymatic, microbial, and chemical properties compared to controls. The microcalorimetric parameters P _max and k were positively correlated, whereas t _max negatively linked with the results of enzymatic, microbial, and chemical properties at p < 0.01. Conversely, Q elucidated non-significant correlation (p < 0.05) to urease (0.248), neutral phosphatase (0.281), dehydrogenase (0.291), MBC (0.283), MBP (0.277), DOC (0.269), DON (0.190), SOM (0.284), and pH (0.047). Our results suggested that calorimetric parameters P _max, t _max, and k are highly sensitive and could be used as indices of soil enzymatic, microbial, and chemical properties, while Q is an indigent indicator.     

Neutron Diffraction Study on the Structure of Aqueous LiNO3 Solutions

Neutron diffraction measurements were carried out at 25 °C for aqueous LiNO₃ heavy water solutions, (*LiNO₃) _x (D₂O)_1?x where x = 0.1, 0.05 and 0.01, in which the ⁶Li/⁷Li isotopic ratios were varied. Structural information on intermolecular nearest neighbor Li⁺···D₂O interactions in the extensive concentration range was derived from the first-order difference function, ?_Li(Q), obtained from the difference in scattering cross sections between ⁶Li- and ⁷Li-enriched sample solutions. The nearest neighbor Li⁺···O distance and coordination number for sample solution with x = 0.1 were determined to be r _LiO = 1.969 (8) Å and n _LiO = 4.12 (6), respectively, corresponding to the four-coordinated Li⁺ ion in the solution. On the other hand, those obtained for the solution with x = 0.01 are r _LiO = 2.00 (2) Å and n _LiO = 6.0 (2), respectively, indicating that hexaaqua Li⁺ is dominant in the dilute solution. These results clearly indicate that a concentration dependence of the hydration number of Li⁺ occurs in the aqueous solutions.