Hollow fiber membrane based H2 diffusion for efficient in situ biogas upgrading in an anaerobic reactor

Bubbleless gas transfer through a hollow fiber membrane (HFM) module was used to supply H₂ to an anaerobic reactor for in situ biogas upgrading, and it creates a novel system that could achieve a CH₄ content higher than 90 % in the biogas. The increase of CH₄ content and pH, and the decrease of bicarbonate concentration were related with the increase of the H₂ flow rate. The CH₄ content increased from 78.4 % to 90.2 % with the increase of the H₂ flow rate from 930 to 1,440 ml/(l?day), while the pH in the reactor remained below 8.0. An even higher CH₄ content (96.1 %) was achieved when the H₂ flow rate was increased to 1,760 ml/(l?day); however, the pH increased to around 8.3 due to bicarbonate consumption which hampered the anaerobic process. The biofilm formed on the HFM was found not to be beneficial for the process since it increased the resistance of H₂ diffusion to the liquid. The study also demonstrated that the biofilm formed on the membrane only contributed 22–36 % to the H₂ consumption, while most of the H₂ was consumed by the microorganisms in the liquid phase.     

Ethanol extraction by supported liquid membrane during fermentation

A supported liquid membrane system was developed for the extraction of ethanol during semicontinuous fermentation of Saccharomyces bayanus. it consisted of a porous Teflon sheet as support, soaked with isotridecanol. This assembly permitted combining biocompatibility, permeation efficiency, and stability. The removal of ethanol from the cultures led to decreased inhibition and, thus, to a gain in conversion of 452 g/L glucose versus 293 g/L glucose without extraction. At the same time, the ethanol volumetric productivity was enhanced 2.5 times, due to an improvement of yeast viability, while the substrate conversion yield was maintained above 95% of its theoretical value. Besides these improvements in fermentation performances, the process resulted in ethanol purification, since the separation was selective towards microbial cells and carbon substrate, and likely selective to mineral ions present in the fermentation broth. For pervaporation, a concentration of ethanol four times greater was obtained in the collected permeate.     

Computer modeling of antibiotic fermentation with on-line product removal

The fermentation of Streptomyces griseus for the production of cycloheximide is similar to other antibiotic fermentations in that product synthesis is subject to feedback regulation and the desired product is degraded in the fermentation broth. The productivity of this fermentation can thus be dramatically increased by removing the antibiotic from the whole broth as it is produced. One means for effecting this on-line product removal is to contact the whole fermentation broth with neutral polymeric resin immobilized in hydrogel beads. The antibiotic adsorbs to the immobilized resin via hydrophobic interactions. In this work, the adsorption of the antibiotic onto the immobilized resin was characterized. A biochemical model of the fermentation was then used to describe the time profiles of biomass, substrate, and antibiotic in a fermentation system in which whole broth is circulated from the fermentor through a continuously stirred extractor containing the adsorbent beads. Various operating conditions were examined to optimize the productivity of the fermentation.     

Determination of short-chain fatty acids in serum by hollow fiber supported liquid membrane extraction coupled with gas chromatography

A method based on hollow fiber supported liquid membrane extraction coupled with a gas chromatograph equipped with flame ionization detector (GC-FID) was developed for the determination of six short-chain fatty acids including acetic acid, propionic acid, i-butyric acid, n-butyric acid, i-valeric acid and n-valeric acid in serum. Hollow fiber supported liquid membrane extraction was employed for preconcentration and clean-up of the samples. The fatty acids were extracted from the acidic donor (diluted serum) into a liquid membrane formed in the wall of the hollow fiber with 10% tri-n-octylphoshphine oxide (TOPO) in di-n-hexyl ether, and then extracted back into a basic acceptor solution filled in the lumen of the hollow fiber. After being acidified with HCl, the acceptor was directly analyzed by GC-FID. The acceptor concentration, donor pH, membrane liquid and extracting time were optimized giving an enrichment factor up to 155 times. The good linearity (r(2)>0.980), reasonable recovery (87.2-121%), and satisfactory intra-assay (8.2-11.5%) and inter-assay (6.1-11.6%) precision illustrated the good performance of the present method. Limits of detection (LOD) ranged from 0.04 to 0.24 microM and limits of quantification (LOQ) varied from 0.13 to 0.80 microM.     

Separation of L-valine from fermentation broths using a supported liquid membrane

A carrier-mediated counter transport process is proposed to separate and to purify an amino acid produced by microbial fermentation. The case of L-valine permeation through a liquid membrane, constituted by a solution of Aliquat 336 in decanol and supported by a hydrophobic microporous membrane, is reported. A mathematical model was developed to estimate distribution coefficients and permeabilities and to predict the influence of hydrodynamic and pH conditions on supported liquid membrane (SLM) performances. Optimum conditions for the transport and the concentration of valine were achieved with synthetic aqueous valine solutions. Series of experiments on fermentation broths, where molasses and biomass contents were varied, permitted pointing out the role of the broth composition on the kinetics and yields of separation. The selectivity of transport of valine by an Aliquat 336/decanol liquid membrane was about 10 toward molasses dyes, 100 toward glucose, and beyond 1000 toward sucrose. This allowed us to achieve the recovery and one step of purification of the product in a single operation. The stability of the Aliquat 336/decanol liquid membrane was sufficient to ensure a selective transport of valine during a continuous run lasting 18 days.     

Recovery of ammonium lactate and removal of hardness from fermentation broth by nanofiltration

Nanofiltration (NF) was investigated as an alternative to desalting electrodialysis (ED) and ion exchange for the recovery of ammonium lactate from fermentation broth. Three commercial NF membranes, NF45, NF70, and NTR-729HF, were characterized with 50 mM NaCl, MgSO(4), and glucose solutions. NF45 membrane was selected because it showed the lowest rejection of monovalent ion, the highest rejection of divalent ion, and the highest rejection of nonpolar molecule. Effects of the operating pressure were investigated in a range of 100-400 psig, on the flux, lactate recovery, and glucose and magnesium removal from a real fermentation broth containing about 1.0 M of ammonium lactate. The flux and recovery rate increased linearly with the pressure. However, lactate rejection also increased with the pressure, lowering the recovery yield. More magnesium ions and glucose were rejected as the pressure was increased, and at 400 psig, for example, magnesium ion was almost completely rejected, highlighting the chance of obviating the necessity of ion exchange to remove hardness, by using NF instead of desalting ED. Membrane fouling was not so severe as expected, considering the complex nature and a rather high concentration of the fermentation broth treated.     

The development of an in situ fermentation electrode calibrator

To allow for replacement and in situ cleaning and calibration of sensors in a fermenter, a probe calibrator was conceived, designed, developed and tested. The calibrator built functioned with a dissolved oxygen electrode but could, if somewhat modified, operate with many other types of sensors. The calibrator is operated by means of an accompanying control unit and is designed to be mounted on a fermenter headplate or through a sidewall penetration. Calibrator performance was tested during a series of fermentations.     

Sequential inactivation of ammonium and glucose transport in Saccharomyces cerevisiae during fermentation

Abstract Ethanol at concentrations above 12% (v/v) in mineral medium with glucose and with ammonium as the only nitrogen source induced rapid inactivation of the ammonium transport system in the strain IGC 3507 of Saccharomyces cerevisiae terminating protein synthesis. Subsequently, when glucose was present, the glucose transport system was irreversibly inactivated. This two-step mechanism may play a decisive role when ethanol stops fermentation by S. cerevisiae , before all the fermentable sugar has been consumed.     

Glycine feeding improves pristinamycin production during fermentation including resin for in situ separation

Seven amino acids were tested as precursors to affect pristinamycin production by a mutant strain derived from Streptomyces pristinaespiralis ATCC25486. Of those, glycine was selected as the best precursor to facilitate both cell growth and pristinamycin production at the feeding time of 36-h incubation and the feeding rate of 0.75 g L⁻¹ flask culture. The optimized time and concentration of glycine feeding were applied to enlarged 3-L bioreactor fermentation with a resin added at the time of 20-h fermentation for in situ separation. As a result, a combination of the glycine feeding and the added resin resulted in the maximal pristinamycin yield of 616 mg L⁻¹ culture 12 h after glycine feeding. The yield from the combined treatment was 1.71-, 2.77- and 4.32-fold of those from the mere glycine and resin treatments and the control, respectively. Other parameters, including intracellular nucleic acid content, animo nitrogen content and pH level, during 72-h fermentation were also given in association with the pristinamycin yields in the different treatments. The results indicate that glycine feeding is an effective approach to enhance pristinamycin production in the culture of S. pristinaespiralis F213 with supplemented resin for in situ separation.     

In situ removal of ammonium ions from hybridoma cell culture media: Selection of adsorbent

Various ion-exchange resins and zeolite Phillipsite-Gismondine were tested for their potential application as adsorbents for thein situ removal of ammonium ions from animal cell culture media in attempting to increase hybridoma cell density and MAb productivity. A zeolite, Phillipsite-Gismondine demonstrated the best performance in terms of NH₄ ⁺ adsorption capacity, selectivity and autoclavability among the various adsorbents tested. The biocompatibility of Phillipsite-Gismondine was also tested and the result showed improvement in cell density, viability, and antibody productivity.     

Role of fungi in cyanogens removal during solid substrate fermentation of cassava

Summary Disinfected cassava root pieces were incubated with and without fungal inoculation. The resulting flours from non-inoculated incubated cassava showed significantly lower (P=0.004) cyanogenic glucoside levels than those from non-incubated cassava, and significantly higher (P < 0.0001) levels than those from the fermented pieces. The fungi played a role in the reduction of the cyanogenic glucoside levels.     

In situ product removal in fermentation systems: improved process performance and rational extractant selection

The separation of inhibitory compounds as they are produced in biotransformation and fermentation systems is termed in situ product removal (ISPR). This review examines recent ISPR strategies employing several classes of extractants including liquids, solids, gases, and combined extraction systems. Improvement through the simple application of an auxiliary phase are tabulated and summarized to indicate the breadth of recent ISPR activities. Studies within the past 5 years that have highlighted and have discussed “second phase” properties, and that have an effect on fermentation performance, are particular focus of this review. ISPR, as a demonstrably effective processing strategy, continues to be widely adopted as more applications are explored; however, focus on the properties of extractants and their rational selection based on first principle considerations will likely be key to successfully applying ISPR to more challenging target molecules.     

Recovery of an alkaline proteinase from fermentation broth using flocculation for cell removal

Summary Recovery of a bacterial alkaline proteinase after treatment of the fermentation broth with 16 different flocculating additives has been investigated. The polyelectrolyte Sedipur TF 5 was the most effective at 150 ppm and pH 7.0–9.0, giving a 74% yield of enzyme activity.     

Multirate state and parameter estimation in an antibiotic fermentation with delayed measurements

This article discusses issues related to estimation and monitoring of fermentation processes that exhibit endogenous metabolism and time-varying maintenance activity. Such culture-related activities hamper the use of traditional, software sensor-based algorithms, such as the extended kalman filter (EKF). In the approach presented here, the individual effects of the endogenous decay and the true maintenance processes have been lumped to represent a modified maintenance coefficient, m(c). Model equations that relate measurable process outputs, such as the carbon dioxide evolution rate (CER) and biomass, to the observable process parameters (such as net specific growth rate and the modified maintenance coefficient) are proposed. These model equations are used in an estimator that can formally accommodate delayed, infrequent measurements of the culture states (such as the biomass) as well as frequent, culture-related secondary measurements (such as the CER). The resulting multirate software sensor-based estimation strategy is used to monitor biomass profiles as well as profiles of critical fermentation parameters, such as the specific growth for a fed-batch fermentation of Streptomyces clavuligerus. (c) 1994 John Wiley & Sons, Inc.     

In situ studies with membrane diffusion chambers of antibiotic resistance transfer in Escherichia coli.

Coliform bacteria were isolated from raw sewage and sewage effluent-receiving waters and tested for their antibiotic susceptibility patterns and their ability to transfer antibiotic resistance to Escherichia coli K-12 C600. An environmental isolate of E. coli (MA527) capable of transferring antibiotic resistance to C600 was mated, both in vitro and in situ, with an antibiotic-sensitive E. coli environmental isolate (MA728). In situ matings were conducted in modified membrane diffusion chambers, in the degritter tank at the Grant Street (Melbourne, Fla.) sewage treatment facility, and in the sewage effluent-receiving waters in Melbourne, Fla. The transfer frequencies in situ were 3.2 x 10(-5) to 1.0 x 10(-6), compared with 1.6 x 10(-4) to 4.4 x 10(-5) observed in vitro. Transfer was shown to occur in raw sewage but was not detected in the effluent-receiving waters. The presence of a 60-megadalton plasmid species in both donor and transconjugants, but not in the recipients, provided physical evidence for the transfer of antibiotic resistance in situ.     

Study of in situ 1-butanol pervaporation from A-B-E fermentation using a PDMS composite membrane: validity of solution-diffusion model for pervaporative A-B-E fermentation

In this study, the application of a new polydimethylsiloxane (PDMS)/dual support composite membrane was investigated by incorporating the pervaporation process into the A-B-E (acetone-butanol-ethanol) fermentation. The performance of the A-B-E fermentation using the integrated pervaporation/fermentation process showed higher biomass concentrations and higher glucose consumption rates than those of the A-B-E fermentation without pervaporation. The performance of the membrane separation was studied during the separation of 1-butanol from three different 1-butanol solutions: binary, model, and fermentation culture solutions. The solution-diffusion model, specifically the mass transfer equation based on Fick's First Law, was shown to be applicable to the undefined A-B-E fermentation culture solutions. A quantitative comparison of 1-butanol separation from the three different solutions was made by calculating overall mass transfer coefficients of 1-butanol. It was found that the overall mass transfer coefficients during the separation of binary, model, and fermentation culture solutions were 1.50, 1.26, and 1.08 mm/h, respectively.     

In situ extraction versus the use of an external column in fermentation

Summary Organic extraction of 2,3-butanediol produced by Klebsiella oxytoca fermentation was studied to determine if the use of an external column offered advantages over in situ extractive fermentation. Dodecanol was chosen from 24 tested solvents, 11 of which were non-toxic to K. oxytoca. Although growth occurred in all shakeflask experiments containing dodecanol, growth was never observed when dodecanol was used in an in situ arrangement in a fermentor. Using dodecanol in an external column, however, resulted in a cell yield of 0.10 g/g d-xylose, and a 2,3-butanediol yield of 0.32 g/g d-xylose, similar to results obtained in control (solventless) experiments. Although the partitioning of 2,3-butanediol in the organic phase was low, this study suggests that external columns, with recycling to the fermentor, can offer substantial advantages over in situ extraction.     

Continuous butanol/isopropanol fermentation in down-flow column reactor coupled with pervaporation using supported liquid membrane

Continuous butanol/isopropanol fermentation with immobilized Clostridium isopropylicum was performed in a downflow column reactor using molasses as the substrate. In order to prevent product inhibition and at the same time obtain high concentration of the products, the column reactor was coupled with a pervaporation module using a supported liquid membrane. The liquid membrane was prepared with oleyl alcohol nontoxic to the microorganism. In comparison with the continuous fermentation without product removal, the specific butanol production rate was 2 times higher. The butanol concentration in the permeate was 230 kg/m(3), which was about 50 times higher than that in the culture broth. A numerical investigation suggested a further increase in the productivity by improving the module construction.     

Improvement of epothilone B production by in situ removal of ammonium using cation exchange resin in Sorangium cellulosum culture

A cation exchange resin was added at different stages in the growth of Sorangium cellulosum cultures to remove excess ammonium, which has a negative influence on the production of the anticancer agent, epothilone. When 8 g L⁻¹ of cation exchange resin were added at the mid-death phase, the ammonium removal reached 83% and the maximum production of epothilone was 14.3 mg L⁻¹, which was 2.6 times greater than that of the control culture.     

Quaternary ammonium compounds in soil: implications for antibiotic resistance development

Quaternary ammonium compounds (QACs) are surface-active, antimicrobial, high production volume (HPV) chemicals with a broad application in agriculture. This review provides a comprehensive overview of (1) predicted and measured concentrations of QACs in soils including their analysis, (2) sequestration mechanisms in soils based on their physicochemical properties and chemical structure, and (3) implications of concentrations and fate of QACs in soils for the proliferation of antibiotic resistance in the environment. Predicted environmental concentrations (PEC) for QACs that are applied to soils with manure are in the order of 3.5 mg kg^?1. Based on literature data, the median PEC of QAC in sewage sludge amended soils is 25 µg kg^?1. The positively charged QACs are mainly sorbed to clay minerals. We propose that QACs might be sequestered in the interlayer regions of layered silicates in clay-rich soils, reducing their acute toxicity, while increasing their persistence. The release of sequestered QACs from soil can still potentially maintain concentration levels that are sufficient to develop antibiotic resistance in the environment.