共查询到20条相似文献,搜索用时 15 毫秒
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Chi-Bun Ching Wah-Koon Teo Khim-Hoong Chu 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1990,47(4):345-355
The performance of an immobilized packed-bed bioreactor for continuous ethanol fermentation was evaluated. Immobilized yeasts were prepared by entrapment in calcium alginate gel. An axial dispersed plug flow model incorporating the effects of substrate and product inhibition on fermentation kinetics was developed. The model equations were solved by the method of orthogonal collocation and the suitability of the reactor model to predict the conversions obtained in this biocatalytic reaction system was assessed. 相似文献
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Van T. Nguyen Wen K. Shieh 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1992,55(4):339-346
Continuous ethanol fermentation of glucose using fluidized bed technology was studied. Saccharomyces cerevisiae were immobilized and retained on porous microcarriers. Over two-thirds of the total reactor yeast cell mass was immobilized. Ethanol productivity was examined as dilution rate was varied, keeping all other experimental parameters constant. Ethanol yield remained high at an average of 0.36 g ethanol g?1 glucose (71% of theoretical yield) as the dilution rate was increased stepwise from 0.04 h?1 to 0.14 h?1. At a dilution rate of 0.15 h?1, the ethanol yield steeply declined to 0.22 g ethanol g?1 glucose (44% of theoretical yield). The low maximum percentage of theoretical yield is primarily due to an extended mean cell residence time, and possibly due to the inhibitory effect of a high dissolved carbon dioxide concentration, enhanced by the probable intermittent levels of low pH in the reactor. Constant ethanol production was possible at a high glucose loading rate of 840 g dm?3 day?1 (attained at a dilution rate of 0.14 h?1). Although the highest average ethanol concentration (97.14 g dm?3) occurred at the initial dilution rate of 0.04 h?1, the peak average ethanol production rate (2.87 g (g yeast)?1 day?1) was reached at a greater dilution rate of 0.11 h-1. Thus, the optimal dilution rate was determined to be between 0.11 h?1 and 0.14 h?1. Ethanol inhibition on yeast cells was absent in the reactor at average bulk-liquid ethanol concentrations as high as 97.14 g dm?3. In addition, zero-order kinetics on ethanol production and glucose utilization was evident. 相似文献
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Mechanistic kinetic models were formulated based on Langmuir-Hinshelwood-Hougen-Watson and Eley-Rideal approaches to describe the kinetics of hydrogen production by the catalytic reforming of concentrated crude ethanol over a Ni-based commercial catalyst at atmospheric pressure, temperature range of 673-863 K, ratio of weight of catalyst to the molar rate of crude ethanol 3472-34722 kg cat s/kmol crude in a stainless steel packed bed tubular microreactor. One of the models yielded an excellent degree of correlation, and was selected for the simulation of the reforming process which used a pseudo-homogeneous numerical model consisting of coupled material and energy balance equations with reaction. The model was solved using finite elements method without neglecting the axial dispersion term. The crude ethanol conversion predicted by the model was in good agreement with the experimental data (AAD%=4.28). Also, the predicted concentration and temperature profiles for the process in the radial direction indicate that the assumption of plug flow isothermal behavior is justified within certain reactor configurations. However, the axial dispersion term still contributed to the results, and thus, cannot be neglected. 相似文献
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Triantafyllos Roukas 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1994,59(4):387-393
The continuous production of ethanol from carob pod extract by immobilized Saccharomyces cerevisiae in a packed-bed reactor has been investigated. At a substrate concentration of 150 g dm?3, maximum ethanol productivity of 16 g dm?3 h?1 was obtained at D = 0·4 h?1 with 62·3% of theoretical yield and 83·6% sugars′ utilization. At a dilution rate of 0·1 h?1, optimal ethanol productivity was achieved in the pH range 3·5–5·5, temperature range 30–35·C and initial sugar concentration of 200 g dm?3. Maximum ethanol productivity of 24·5 g dm?3 h?1 was obtained at D = 0·5 h?1 with 58·8% of theoretical yield and 85% sugars′ utilization when non-sterilized carob pod extract containing 200 g dm?3 total sugars was used as feed material. The bioreactor system was operated at a constant dilution rate of 0·5 h?1 for 30 days without loss of the original immobilized yeast activity. In this case, the average ethanol productivity, ethanol yield (% of theoretical) and sugars′ utilization were 25 g dm?3 h?1, 58·8% and 85·5%, respectively. 相似文献
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Sheng H. Lin 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1991,50(1):17-26
Optimal feed temperature was determined for a nonisothermal immobilized enzymatic reaction with enzyme deactivation in a packed-bed reactor. The optimal feed temperature was obtained by maximizing the average substrate conversion over a given reaction period. Simulation showed the optimal feed temperature to be strongly dependent on the flow dispersion, the reaction activation energy, the corresponding enzyme inactivation energy and the heat of reaction. It was also observed that in a plug flow reactor the enzyme reaction generally exhibited a lower optimal feed temperature and higher substrate conversion than in a continuously stirred tank reactor. 相似文献
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Ins Joekes Paulo J. S. Moran J. Augusto R. Rodrigues Renato Wendhausen Eduardo Tonella Flvia Cassiola 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1998,73(1):54-58
Saccharomyces cerevisiae (CCT 3174 and commercial baker's yeast) was immobilized by adsorption onto chrysotile. The adsorbed yeast cells were easily washed out, but cells grown in situ were strongly attached by entrapment by chrysotile microfibres. In fermentation experiments with 30% (w/v) glucose solution, the immobilized cells showed a 1·3-fold increase in initial reaction velocity. For immobilized CCT 3174, the final ethanol yield was 26% higher than that with free cells. © 1998 Society of Chemical Industry 相似文献
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F. Gdia C. Casas C. Sol 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1985,35(2):139-144
Ethanol production by yeast cells immobilised in carrageenan gel beads and operated in a continuous tubular reactor reached 15 g dm?3 h?1 with a glucose feed of 165 g dm?3; a glucose residence period of 4.6 h was noted. The minimal cell loading to obtain uniform particles was 104 colony-forming units per g of gel, although particles achieved a content of 108 CFU g?1 independent of the initial cell concentration. Scanning electron and phase contrast microscopy confirmed that growth inside the gel beads was probably limited by substrate diffusion through the denser outer layer observed. 相似文献
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zer G Dursun D
zer M Elibol 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2000,75(11):1061-1065
The growth kinetics and mass transfer characteristics of Saccharomyces cerevisiae in a cocurrent downflow contacting reactor (CDCR) were studied for various glucose concentrations at constant air and liquid flow rates. Increasing glucose concentration increased the biomass concentration thus resulting in an increase in the volumetric oxygen uptake rate. The volumetric mass transfer coefficient, kLa, however, decreased with increasing glucose concentration. It was observed that the growth of S cerevisiae in the CDCR would fit the classical Monod kinetics and the maximum specific growth rate was determined to be 0.545 h−1. © 2000 Society of Chemical Industry 相似文献
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Vanillin is an important flavour. Semi-synthetic vanillin can be produced by the oxidation of lignin. Experimental studies leading to vanillin production in a batch reactor and a structured bubble column reactor (SBCR) lead us to the conclusion that the SBCR could have non-idealities such as dispersion. The radial and axial liquid-phase dispersion within the packed criss-crossing sandwich structures of Mellapak-750Y had been studied. A 2D model accounting for axial and radial velocities and dispersion was formulated and solved. The model predictions were compared with that of an experimental residence time distribution curve. The axial dispersion coefficient of the liquid phase is of the same order of magnitude as the radial dispersion coefficient. The reaction kinetics available in literature is adopted for the present study. Model for the SBCR was formulated and simulated using commercial modeling software. Simulation experiments were conducted in a SBCR. The effect of the following parameters on the yield of vanillin is studied: lignin concentration, lignin molecular weight, oxygen partial pressure and reaction temperature. It can be said that lignin molecular weight is a crucial parameter in vanillin production. 相似文献
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Nasibuddin Qureshi J. S. Pai D. V. Tamhane 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1987,39(2):75-84
Ethanol production by immobilised yeast cells in packed-bed column reactors was significantly affected by the hold-up of CO2 produced during the fermentation. Compartmentalisation of the reactor minimises CO2 hold-up and prevents flotation of immobilised cell beads during operation and bead rupture during shut-down conditions. In a reactor of dimensions 2·2 × 60 cm, a rate of ethanol production of 5·11 g h?1 at a dilution rate of 1·27 h?1 was achieved, when 18% (w/v) glucose solution was fed at the bottom at pH 5·5 and temperature 33–35°C. In larger reactors of sizes 4 ×; 40 cm and 8 × 80 cm the rates of ethanol production and CO2 hold-ups were 5·11 and 5·37 g h?1 and 48·66% and 40·66% and 40·79% of the void volume at dilution rates of 1·27 h?1 and 1·67 h1, respectively. The CO2 hold-ups in column reactors (4 × 40 cm) held in inclined (43° from horizontal) or horizontal positions were 41·33% and 46·67% of the void volume, respectively. Double and triple series reactors (each of dimensions 2·2 × 60 cm) showed better performance than a single verticle reactor (2·2 × 60 cm). 相似文献
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Static mixers were introduced in the draught tube of a three-phase, concentric tube type airlift bioreactor, resulting in a 30% increase in ethanol productivity during glucose fermentation with a highly flocculent strain of Saccharomyces cerevisiae. Increased productivity was obtained as a consequence of the floe size reduction provoked by the new design of the draught tube and of the smaller applied aeration rates, allowing a higher dilution rate to be used. Steady state data at different dilution rates were measured for both systems and the results were compared in terms of specific consumption / production rates and ethanol productivity. An approach based on heterogeneous catalysis principles was used in order to consider the presence of porous yeast flocs. Total glucose conversion was achieved at a dilution rate of 0.34 h?1. The smaller floe size contributed to the higher observed reaction rates by reducing diffusional limitations inside the flocs. The respiratory quotient had a constant value (around 23) at all dilution rates, meaning that the metabolic state of the cells in the flocs remained constant, having a strong fermentative metabolism. 相似文献
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Lowie E. S. Brink Johannes Tramper 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1987,37(1):21-44
The production of propene oxide from propene and oxygen by non-growing cells entrapped in calcium alginate was used to study the behaviour of a packed-bed immobilized-cell reactor operated with an organic solvent as the substrate reservoir. As a result of the high solubility of propene in the solvent used, n-hexadecane, oxygen was considered to be the limiting substrate. Dilution of the biocatalyst bed with small glass particles appeared necessary to attain a high liquid/solid contacting efficiency between the hydrophilic gel particles and the hydrophobic solvent. The bed dilution had the advantage of avoiding bed compaction and reducing pressure drops. The use of an organic solvent as the transport medium prevented oxygen depletion along the length of the packed-bed reactor. This eliminated the need for a separate gas phase in the bioreactor. A mathematical reactor model was developed to describe the combined effects of contacting pattern and external and internal diffusion limitations on the instrinsic kinetics of the immobilized cells. Experiments with the packed-bed immobilized-cell reactor were performed using an aqueous solution or n-hexadecane as the reaction medium. Predicted oxygen conversions compared favourably to the observed values without the need for fitting factors. 相似文献
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Sebastià Puig Marta Coma Mark CM van Loosdrecht Jesús Colprim Maria D Balaguer 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2007,82(10):898-904
BACKGROUND: When organic matter is limiting for biological nutrient removal (BNR) from wastewater, external organic carbon can be added to a wastewater treatment plant (WWTP). This increases the overall treatment cost, so the choice of substrate is critical. The effect of using ethanol as the carbon source for BNR is investigated. RESULTS: The results clearly showed that using ethanol as a carbon source is a promising strategy for removing nutrients from wastewater. Effluent concentrations of 3.0 mg total nitrogen (TN) L?1 (96% N removal efficiency) and 0.05 mg phosphate (P‐PO4) L?1 (99.9% P removal efficiency) were obtained. Furthermore, tests performed in order to identify the carbon source used by polyphosphate‐accumulating organisms (PAOs) showed that the phosphorus release/carbon uptake ratio using ethanol (0.41 mmol P mmol?1 C) was slightly lower than that with acetate (0.50 mmol P mmol?1 C) but close to that with propionate (0.42 mmol P mmol?1 C). CONCLUSION: Therefore, taking into account the results presented for ethanol‐acclimatised biomass and the fact that the cost of ethanol is lower than that of acetate or propionate, ethanol can be considered as an alternative carbon source if one is needed in a WWTP. Copyright © 2007 Society of Chemical Industry 相似文献
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Shoubao Yan Pingchao Wang Zhijun Zhai Jianming Yao 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2011,86(5):731-738
BACKGROUND: Continuous ethanol fermentation of concentrated food waste hydrolysates has been studied. The process was carried out in an immobilized cell reactor with beads of calcium‐alginate containing immobilized Saccharomyces cerevisiae H058 at temperature 30 °C and pH 5.0. RESULTS: The total residual sugar decreased with increase of hydraulic retention time (HRT) under various reducing sugar concentrations. Ethanol production by immobilized cells increased with increase in HRT, regardless of the substrate concentrations employed. The highest ethanol concentration of 89.28 g L?1 was achieved at an HRT of 5.87 h and reducing sugar concentration of 200 g L?1. At an HRT of 1.47 h, the maximum volumetric ethanol productivity of 49.88 g L?1 h?1 and the highest ethanol yield of 0.48 g g?1 were achieved at reducing sugar concentration of 160 and 200 g L?1, respectively. The difference between the fresh and the 30‐day Ca–alginate immobilized cell was also shown by scanning electronic micrographs of beads taken from their outer and inner surfaces. CONCLUSIONS: Continuous ethanol production from concentrated food waste hydrolysates using immobilized yeast cells is promising in view of the high ethanol productivity obtained at relatively high conversion and excellent reactor stability. Copyright © 2011 Society of Chemical Industry 相似文献
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