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Biochemical Engineering Journal (v.22, #3)
Cholesterol recovery from inclusion complex of β-cyclodextrin and cholesterol by aeration at elevated temperatures by Shinjiro Yamamoto; Hajime Kurihara; Takaaki Mutoh; Xin-hui Xing; Hajime Unno (pp. 197-205).
Recovery of cholesterol from an inclusion complex of β-cyclodextrin (βCD) and cholesterol with a βCD/cholesterol molar ratio of three dissolved in water, by dissociation at elevated temperatures, was examined. Free cholesterol released from the inclusion complex was observed as a solid, showing that removal of free cholesterol from the inclusion complex is possible. In order to effectively remove the cholesterol in solution from the inclusion complex, a foam separation method was examined. The free cholesterol was brought up to the surface of the liquid by bubbles due to a hydrophobic interaction, while βCD, which was still dissolved in water, was not concentrated during bubbling. The maximum free cholesterol removal ratio, defined as the maximum free cholesterol concentration reached after bubbling to the initial cholesterol concentration in the complex, increased with increasing temperature. These results indicate that elevated temperatures enhance the removal of cholesterol from the inclusion complex. However, complete removal of cholesterol from the inclusion complex was never achieved, implying that the inclusion complex might have dissociable and undissociable forms. A model was proposed for the free cholesterol release, derived from sequential dissociation of the inclusion complex releasing the βCD dimer, and it successfully expressed the experimental data.
Keywords: Inclusion complex; β-Cyclodextrin; Cholesterol; Foam separation; Modelling; Production kinetics
The recovery of acetic acid with sulfur dioxide by Yonghui Shi; Maohong Fan; Na Li; Robert C. Brown; Shihwu Sung (pp. 207-210).
This paper studies the reaction between SO2 and calcium acetate, which potentially can be used to recover acetic acid from the anaerobic fermentation broth with a SO2 waste stream. The conversion of given amounts of calcium acetate to acetic acid was evaluated under different reaction temperatures and flow rates of SO2. Analyses of concentrations of the produced acetic acid indicated that the reactions between SO2 and calcium acetate were complete under all experimental conditions.
Keywords: Acetic acid; Calcium acetate; Mixing; Separation; Sulfur dioxide; Waste treatment
Application of solid-state fermentation to ligninolytic enzyme production by S. Rodríguez Couto; M A. Sanromán (pp. 211-219).
Solid-state fermentation (SSF) has received new interest not only from researchers but also from industry. This technique has become a very attractive alternative to submerged fermentation (SmF) for specific applications due to the recent improvements in reactor designs. The present paper reviews the production of ligninolytic enzymes by SSF technique.
Keywords: Bioreactors; Filamentous fungi; Enzyme production; Organic wastes; Solid-state fermentation; Support
A low cost porous polyvinylbutyral membrane for BSA adsorption by Deniz Tanyolaç; Hakan Sönmezışık; Ahmet R. Özdural (pp. 221-228).
In this work, a feasible membrane was prepared in uniform thickness for the range 120–145μm from a commercial resin, Mowital® B30HH (polyvinylbutyral) using phase inversion technique. For the production of the membrane, the most appropriate solvent, polymer concentration, temperature and the composition of casting solution were investigated. Macroporous membranes were produced with 6–20% (w/v) polymer concentration using N, N-dimethylacedamid and water as the solvent and casting solution, respectively, at 20°C, determined to be the optimum chemicals and conditions. It was found that pore size, pore density, water permeation rate, water content, and elongation of the membranes decreased while breakpoint stress increased with the increase of polymer concentration. FT-IR studies proved the abundance of hydroxyl groups on the membrane surface, which were activated later by glutaraldehyde for bovine serum albumin (BSA) separation. Preliminary adsorption runs were conducted at pH 5.0, determined to be the optimum for BSA adsorption, with the membrane prepared at 9% polymer concentration in a batch reactor. For 10mg/ml initial BSA concentration, the adsorbed BSA was calculated as 427μg/cm2 (35.44mg/ml membrane) denoting a remarkable capacity for BSA adsorption compare to those of other membranes in literature.
Keywords: Membrane; Phase inversion; Polyvinylbutyral; Bovine serum albumin (BSA); Adsorption
Production of a Rhodococcus erythropolis IGTS8 biocatalyst for DBT biodesulfurization: influence of operational conditions by Carolina H. del Olmo; Victoria E. Santos; Almudena Alcon; Felix Garcia-Ochoa (pp. 229-237).
The influence of operational conditions, such as temperature (from 26 to 36°C), pH (with and without control) and dissolved oxygen concentration (with and without control), has been studied during growth in batch of Rhododoccus erythropolis IGTS8. This bacteria has the ability to convert dibenzothiophene (DBT) into 2-hydroxybyphenyl (HBP), desulfurizing the organic molecule. In order to get the best conditions to obtain desulfurizing cells, a parameter ( DBDS) including both biomass concentration and time to reach a particular percentage of desulfurizing capability ( XBDS) has been employed. The optimum value of DBDS has been obtained under the following working conditions: 30°C of temperature, pH 6.5 and a dissolved oxygen concentration constant value of 10% saturation.A kinetic model based on a logistic equation was applied to describe biomass concentration during R. erythropolis IGTS8 growth. Kinetic model parameters ( μ andCXmax) were obtained under several operational conditions. A model was applied to describe biodesulfurization capability evolution during growth. Predicted values of biomass concentration and biodesulfurizing capability percentage achieved by the cells can be obtained during R. erythropolis IGTS8 growth, with very close values to those found experimentally.
Keywords: Biodesulfurization; Optimisation; Growth kinetic; Modelling; Dibenzothiophene; Rhodococcus erythropolis; IGTS8
Electro-chemically improved bio-degradation of municipal sewage by Lehua Zhang; Jinping Jia; Youchun Zhu; Nanwen Zhu; Yalin Wang; Ji Yang (pp. 239-244).
Biofilm-electrode reactor and activated sludge-electrode reactor were developed based on biofilm reactor and activated sludge reactor. The effect of electro-chemical reaction on the bio-degradation of municipal sewage was examined by the comparison experiments. Denitrification was improved by combining biofilm process with electro-chemical effect in a single novel reactor and sludge bulking was compacted for the introduction of electrode in activated sludge system.
Keywords: Biodegradation; Wastewater treatment; Biofilms; Activated sludge; Bio-electro reactor; Denitrification; Municipal sewage
Transesterification of substituted ethanols - modelling studies by Sunil S. Bhagwat; H.S. Bevinakatti; Mukesh Doble (pp. 253-259).
Kinetic and molecular modeling of transesterification of ethyl acetate and substituted ethanols with porcine pancreatic lipase (PPL) and Candida cylindracea lipase (YL) is studied. Competitive product inhibition model is able to explain the observed behaviour well. The molecular dimensions of the substrates and the products, thermodynamic parameters and charges were estimated by molecular modelling based on minimum energy conformation and semi empirical quantum mechanical calculations. A strong correlation exists in the case of YL between conversion and (a) the cross sectional area of the alcohols, (b) difference between minimum energies of ester and alcohol, and (c) difference between the electrostatic potential volume of ester and alcohol. Only a weak correlation exists between these parameters, in the case of PPL whereas a strong correlation exists for PPL between conversion and charge on the alcohol oxygen of the substrate. Linear regression equations were developed for predicting the conversion based on these factors. Artificial neural networks (ANN) were employed to bring out the dependence of the catalytic activity on the molecular structure of the substituted ethanol. ANN model with charge on oxygen and molecular weight seems to fit the maximum reaction velocity in the case of PPL very closely. In the case of YL, ANN model with electrostatic potential volume difference and van der Waals volume fits the data satisfactorily. The variation of the maximum velocity with these parameters was also predicted using artificial neural network analysis. These studies indicate that both the lipases behave in different manner for the transesterification reaction.
Keywords: Transesterification of substituted ethanols; Lipase catalysis; Structure-property relationship; Minimum energy conformation; Product inhibition model; Semi-empirical quantum mechanics; Artificial neural networks