Electrodialysis of acetate fermentation broths

Electrodialysis (ED) shows good potential for downstream processing of acetate fermentation broths, to separate acetic acid while unreacted glucose and other nutrients are partially recycled back to the fermenter. With conventional anion- and cation-exchange membranes, higher current increased acetate flux, water flux, and energy consumption. Multiple ED stacks connected in series with unequal initial volumes for a batch process maximized acetate concentration in the concentrating stream to 134g/L calcium-magnesium acetate (CMA) in the fermentation broth at pH 6.8. Back-transport of acetate from the product into the feed stream and water transport limit the maximum concentration possible. Cost of ED is about $295/ton acetate for the CMA broth.     

Recovery of organic acids from fermentation broths

Rising concerns over the use of fossil resources have generated renewed interest in the production of commodity chemicals via fermentation. Organic acids are a particularly attractive target because their functionality enables downstream catalytic upgrading to a variety of compounds. In this article, we survey how common technical issues are addressed in the recovery schemes for several organic acids. We present results for the recovery of acetate using a new method based on amine complexation. Our reactive separation scheme produces a high-purity product, is energy efficient, and avoids the coproduction of a waste salt coproduct, all prerequisites for a large-scale production process.     

Modelling the clarification of lactic acid fermentation broths by cross-flow microfiltration

This work is focused on modelling microfiltration for clarifying fermentation broths for the production of lactic acid. The hydraulic resistance-in-series model was used with membrane resistance, bacterial cell cake resistance, adsorption resistance and solute concentration polarisation resistance. Most of the model parameters were determined from independent experiments. This model was applied for microfiltrations operated either under constant transmembrane pressure or under constant permeate flux. Resistances due to adsorption and to solute concentration polarisation dominated. Bacterial cake resistance was found to be very low or equal to zero when microfiltration was below the critical flux.     

Rheological behavior of fermentation broths in antibiotic industry

An experimental study of rheological behavior of three morphological types of fermentation broths in relation to process conditions was carried out in industrial and pilot-plant bioreactors. Three industrially manufactured antibiotic broths were studied: Cephalosporin C (fungal), tylosin (actinomycetic), and apramycin (proactinomycetic), in which the rheology may cause real problems. A viscometer with coaxial cylinders and six-blade impeller was used for rheological measurements. The shear rates range in which both the instruments give similar results was determined. During the experiments rheological and morphological behavior, pH, activity, biomass concentration, fats, glucose, and nitrogen concentrations were studied. All the broths studied exhibited nonNewtonian behavior, which could be described with Ostvald-de-Waele power-law model. It was found that the rheological behavior of the broths during the process is closely related to biomass concentration and morphological changes of mycelia, so that viscosity could be used as a parameter for process monitoring and regulation. A set of experiments on oxygentransfer improvement in the case of the most viscous tylosin broths by water addition was also done.     

Downstream processing of lactic acid-whey permeate fermentation broths by hollow fiber ultrafiltration

Membrane filtration is a suitable method for cell harvesting and clarification of fermentation broths. Hollow fiber ultrafilters gave essentially 100% rejection ofL. bulgaricus cells from a whey permeate fermentation broth. A combination of low pressures and high velocity generally gave the best permeate flux. Fermentation media components (in this case, from the whey permeate) contributed significantly to fouling. Considering the pressure limitations of the current generation of asymmetric hollow fiber modules and the changes in physical properties of the fermentation broths, a cell concentration of 100–150 g/L could be obtained with the flux still relatively high (above 20LMH), although the chemical compatibility of the membrane module itself under long-term exposure to high acid conditions should be considered.     

Simple and rapid gas-chromatographic determination of volatile metabolites in fermentation broths

Bacillus subtilis K (AJ 1992) responds very rapidly to variations in oxygen supply, excreting volatile acetoin and meso-2,3-butanediol; their relative amounts are determined by the supply of dissolved oxygen. A complex medium was used to grow B. subtilis. Initially, packed-column gas chromatography was used. The samples were centrifuged and then directly injected. The precision was about 5%. A complete analysis lasted about 22 min. To get better results a wide-bore capillary column was used. Problems with reproducibility were encountered when split injection was used, whereas a packed-column inlet and autosampler/injection gave precise results for clean samples (s.d. 0.7% for acetoin, 3.3% for 2,3-butanediol). Slight nonlinearities were observed for butanediol below 0.5 gl^?1. A complete analysis was then possible within 10 min. Both types of column allowed meso- and d,l-2,3-butanediol to be distinguished. High concentration of molasses and larger amounts of silicone antifoam agent caused peak area drift, especially for butanediol. Data evaluation based on 2 to 3 reference injections, and linear interpolation allowed an accuracy better than ± 5% for both volatile components. Total culture broth including cells could be injected directly. Samples containing xanthan gum could be injected without any pretreatment. The method developed may be applicable in many bioprocesses where volatile components have to be determined.     

An integrated platform for gas-diffusion separation and electrochemical determination of ethanol on fermentation broths

An integrated platform was developed for point-of-use determination of ethanol in sugar cane fermentation broths. Such analysis is important because ethanol reduces its fuel production efficiency by altering the alcoholic fermentation step when in excess. The custom-designed platform integrates gas diffusion separation with voltammetric detection in a single analysis module. The detector relied on a Ni(OH)₂-modified electrode. It was stabilized by uniformly depositing cobalt and cadmium hydroxides as shown by XPS measurements. Such tests were in accordance with the hypothesis related to stabilization of the Ni(OH)₂ structure by insertion of Co²⁺ and Cd²⁺ ions in this structure. The separation step, in turn, was based on a hydrophobic PTFE membrane, which separates the sample from receptor solution (electrolyte) where the electrodes were placed. Parameters of limit of detection and analytical sensitivity were estimated to be 0.2% v/v and 2.90 μA % (v/v)⁻¹, respectively. Samples of fermentation broth were analyzed by both standard addition method and direct interpolation in saline medium based-analytical curve. In this case, the saline solution exhibited ionic strength similar to those of the samples intended to surpass the tonometry colligative effect of the samples over analyte concentration data by attributing the reduction in quantity of diffused ethanol vapor majorly to the electrolyte. The approach of analytical curve provided rapid, simple and accurate analysis, thus contributing for deployment of point-of-use technologies. All of the results were accurate with respect to those obtained by FTIR method at 95% confidence level.     

Lactic acid fermentation and adsorption on PVP

Applied Biochemistry and Biotechnology - Lactic acid was produced by immobilizedLactobacillus delbreückii cells in a fixedbed reactor and then separated by a column packed with...     

Spreading of proteins and its effect on adsorption and desorption kinetics

The kinetics of adsorption of lysozyme and alpha-lactalbumin from aqueous solution on silica and hydrophobized silica has been studied. The initial rate of adsorption of lysozyme at the hydrophilic surface is comparable with the limiting flux. For lysozyme at the hydrophobic surface and alpha-lactalbumin on both surfaces, the rate of adsorption is lower than the limiting flux, but the adsorption proceeds cooperatively, as manifested by an increase in the adsorption rate after the first protein molecules are adsorbed. At the hydrophilic surface, adsorption saturation (reflected in a steady-state value of the adsorbed amount) of both proteins strongly depends on the rate of adsorption, but for the hydrophobic surface no such dependency is observed. It points to structural relaxation ("spreading") of the adsorbed protein molecules, which occurs at the hydrophobic surface faster than at the hydrophilic one. For lysozyme, desorption has been studied as well. It is found that the desorbable fraction decreases after longer residence time of the protein at the interface.     

Polymer adsorption and its effect on the stability of hydrophobic colloids

Summary As a first step in a study on the interaction between polymers and hydrophobic colloids we investigated in detail the adsorption of polyvinyl alcohol (PVA) on aqueous silver iodide sols. The adsorption is irreversible. Adsorption isotherms are of the highaffinity type. The amount adsorbed increases with molecular weight and with the fraction of acetate groups in the PVA chain. The effective thickness of the adsorbed layer was determined viscosimetrically and independently checked by an electrophoretic method. Double layer studies enabled the determination of the occupancy of the first layer on the surface by polymer segments. It was found that even at maximal coverage with polymer this layer is still about 30% void. The combination of these data enabled the assessment of the polymer segment distribution. It was found that with not too low coverages the distribution isHoeve- like. The distribution, thus obtained reflects itself in the flocculation of AgI sols by PVA.Presented at the 25th Colloid-Meeting in Munich, October 13–15, 1971     

Modeling of oxygen adsorption on silver

Different adsorption forms of oxygen on silver are discussed. Four main types of oxygen forming at different temperatures and oxygen pressures have been distinguished. A kinetic model describing the formation and transformations of the oxygen forms and taking into account the surface amorphization has been proposed. Numerical modeling of stationary concentrations using this model gives evidence for a temperature window ΔT=500–800 K, where a quasimolecular oxygen state (E=530.5 eV, T_des=800–900 K) can exist at high oxygen pressures.     

Dissociative adsorption of oxygen on aluminum

The initial steps of aluminum oxidation were studied by scanning tunnel microscopy (STM). A procedure was proposed and implemented for obtaining information on the migration of atoms formed by dissociative adsorption from the measurement of distances between adsorbed atoms visible in STM images.Translated from Kinetika i Kataliz, Vol. 46, No. 1, 2005, pp. 137–140. Original Russian Text Copyright © 2005 by Andreev, Grishin, Dalidchik, Kovalevskii, Shub.     

High performance liquid chromatographic analysis of fermentation broths: cephalosporin C and tylosin.

Procedures are described for the analysis of cephalosporin C or tylosin in fermentation broths by high performance liquid chromatography (HPLC). Quantitation of the major components in cephalosporin C broths was done by a system involving separation by an ion-pair technique. Tylosin data were obtained using a reverse phase method. A method of equating uv potency of tylosin to microbiological potency is discussed. A comparison of HPLC with a microbiological method for the determination of tylosin concentration is also made.     

The effect of doping of the ultradispersed nickel powder by pyrocarbon on oxygen adsorption and Oads + CO reaction

Oxygen adsorption and chemisorption and the kinetics of interaction between adsorbed oxygen and CO on nickel ultradispersed powder (average size of particles, 20 nm) are studied. The ultradispersed nickel powder was dosed by the products of pyrolysis of chemisorbed ethylene (pyrocarbon) in the amount of 0.1–1.6 of a monolayer. The spectra of ferromagnetic resonance of the ultradispersed nickel powder before and after ethylene adsorption and pyrolysis and after adsorption and chemisorption of oxygen and its reduction by hydrogen are recorded. The magnetization of ultradispersed nickel powder increases upon dosing the surface with ethylene (C₂H_4ads) and pyrocarbon in the amount of 0.5 of a monolayer. Pyrocarbon inhibits the O_ads + CO reaction. The reaction orders with respect to O_ads and CO and the experimental activation energy change. The effects of small (less than a monolayer) and large (more than a monolayer) amounts of the modifying agent are different.     

Recovery and purification of lactic acid from fermentation broth by adsorption

Applied Biochemistry and Biotechnology - Riedel-de-Haen VI-15, Dowex MWA-1 and Amberlite IRA-35 were employed for lactic acid recovery using model fermentation broth. The broth was first acidified...     

Sulfur fixation on bagasse activated carbon by chemical treatment and its effect on acid dye adsorption

Heteroatoms are known to introduce specific surface functionalities that can enhance the adsorption properties of carbons. Sulfur fixation on bagasse-activated carbon was conducted by a low temperature chemical treatment with sulfuric acid followed by physical activation with CO₂ at 900?°C. The effect of sulfur fixation on the surface chemical properties of bagasse-activated carbons were investigated and on their subsequent acid dye removal (CIBA AB80) behavior. Surface chemical development were examined and followed using Fourier transform infrared spectroscopy (FTIR), heteroatom analysis and carbon surface acidity. Functional group stability with thermal treatment was also investigated. The textural properties of the activated carbons were characterized by nitrogen adsorption. Chemical pre-treatment and gasification was able to fix up to 0.2 wt% of sulfur on the activated carbon. Although the sulfur fixed by chemical treatment is low, this method introduced several advantages in comparison to fixation by thermal methods. The chemical method did not interfere with the textural development of the carbon, as found in thermal methods. In addition, the surface chemistry generated by these levels of sulfur groups was sufficient to increase the uptake of acid blue dyes by more than 700% based on adsorption capacities normalized by the surface area of the carbon.     

MFI zeolite as adsorbent for selective recovery of hydrocarbons from ABE fermentation broths

1-Butanol and butyric acid are two interesting compounds that may be produced by acetone, butanol, and ethanol fermentation using e.g. Clostridium acetobutylicum. The main drawback, restricting the commercialization potential of this process, is the toxicity of butanol for the cell culture resulting in low concentrations of this compound in the broth. To make this process economically viable, an efficient recovery process has to be developed. In this work, a hydrophobic MFI type zeolite with high silica to alumina ratio was evaluated as adsorbent for the recovery of butanol and butyric acid from model solutions. Dual component adsorption experiments revealed that both butanol and butyric acid showed a high affinity for the hydrophobic MFI zeolite when adsorbed from aqueous model solutions. Multicomponent adsorption experiments using model solutions, mimicking real fermentation broths, revealed that the adsorbent was very selective to the target compounds. Further, the adsorption of butyric and acetic acid was found to be pH dependent with high adsorption below, and low adsorption above, the respective pKa values of the acids. Thermal desorption of butanol from MFI type zeolite was also studied and a suitable desorption temperature was identified.