Bioreactors Research Papers - Academia.edu (original) (raw)

Rheology Sludge Viscosity a b s t r a c t Rheological characterization is of crucial importance in sludge management both in terms of biomass dewatering and stabilization properties and in terms of design parameters for sludge handling operations. The sludge retention time (SRT) has a significant influence on biomass properties in biological wastewater treatment systems and in particular in membrane bioreactors (MBRs). The aim of this work is to compare the rheological behaviour of the biomass in a MBR operated under different SRTs. A bench-scale MBR was operated for 4 years under the same conditions except for the SRT, which ranged from 20 days to complete sludge retention. The rheological properties were measured over time and the apparent viscosity was correlated with the concentration of solid material when equilibrium conditions were reached and maintained. The three models most commonly adopted for rheological simulations were evaluated and compared in terms of their parameters. Then, steady-state average values of these parameters were related to the equilibrium biomass concentration (MLSS). The models were tested to select the one better fitting the experimental data in terms of mean root square error (MRSE). The relationship

- by and +1
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- Water, Statistical Analysis, Rheology, Multidisciplinary

Bioreactors provide a dynamic culture system for efficient exchange of nutrients and mechanical stimulus necessary for the generation of effective tissue engineered bone grafts (TEBG). We have shown that biaxial rotating (BXR) bioreactor-matured human fetal mesenchymal stem cell (hfMSC) mediated-TEBG can heal a rat critical sized femoral defect. However, it is not known whether optimal bioreactors exist for bone TE (BTE) applications. We systematically compared this BXR bioreactor with three most commonly used systems: Spinner Flask (SF), Perfusion and Rotating Wall Vessel (RWV) bioreactors, for their application in BTE. The BXR bioreactor achieved higher levels of cellularity and confluence (1.4e2.5x, p < 0.05) in large 785 mm 3 macroporous scaffolds not achieved in the other bioreactors operating in optimal settings. BXR bioreactor-treated scaffolds experienced earlier and more robust osteogenic differentiation on von Kossa staining, ALP induction (1.2e1.6Â, p < 0.01) and calcium deposition (1.3 e2.3Â, p < 0.01). We developed a Micro CT quantification method which demonstrated homogenous distribution of hfMSC in BXR bioreactor-treated grafts, but not with the other three. BXR bioreactor enabled superior cellular proliferation, spatial distribution and osteogenic induction of hfMSC over other commonly used bioreactors. In addition, we developed and validated a non-invasive quantitative micro CT-based technique for analyzing neo-tissue formation and its spatial distribution within scaffolds.

- by Swee Teoh
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- Materials Science, Biomaterials, Cell Adhesion, Medicine

The construction of expression vectors encoding either the human insulin A-or B-chains fused to a synthetic peptide and the temperature-induced expression of the recombinant genes in Escherichia coli are reported. Using this two-chain approach we also describe the separate isolation of the insulin A-and B-chains from inclusion bodies and their subsequent assembly into native human insulin. The production of the insulin fusion proteins were carried out in high-cell density fed-batch cultures using a synthetic medium with glucose as sole carbon and energy source. The expression of the recombinant genes by temperature-shift in high-cell density cultures of recombinant E. coli resulted in product yields of grams per litre of culture broth, e.g. 4.5 g of insulin B-chain fusion protein per litre of culture broth. This translates into an expression yield of about 800 mg of the insulin B-chain per litre of culture. Under similar cultivation conditions the expression yield of the insulin A-chain corresponds to approximately 600 mg per litre of culture. The metabolic burden imposed on the recombinant cells during temperature-induced production of insulin fusion proteins in high-cell density cultures is reflected in an increased respiratory activity and a reduction of the biomass yield coefficient with respect to glucose.

- by Navin Khanna
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- Engineering, Technology, Biotechnology, Gene expression

The anaerobic digestion of glycerol derived from biodiesel manufacturing, in which COD was found to be 1010 g/kg, was studied in batch laboratory-scale reactors at mesophilic temperature using granular and non-granular sludge. Due to the high KOH concentration of this by-product, H 3 PO 4 was added to recover this alkaline catalyst as agricultural fertilizer (potassium phosphates). Although it would not be economically viable, a volume of glycerol was distilled and utilised as reference substrate. The anaerobic revalorisation of glycerol using granular sludge achieved a biodegradability of around 100%, while the methane yield coefficient was 0.306 m 3 CH 4 /kg acidified glycerol. Anaerobic digestion could be a good option for revalorising this available, impure and low priced by-product derived from the surplus of biodiesel companies. The organic loading rate studied was 0.21-0.38 g COD/g VSS d, although an inhibition phenomenon was observed at the highest load.

- by Maria Ana Santos
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- Manufacturing, Catalysis, Kinetics, Biotechnology

Hydrogen gas can be recovered from the microbial fermentation of organic substrates at high concentrations when interspecies hydrogen transfer to methanogens is prevented. Two techniques that have been used to limit methanogenesis in mixed cultures are heat treatment, to remove nonsporeforming methanogens from an inoculum, and low pH during culture growth. We found that high hydrogen gas concentrations (57-72%) were produced in all tests and that heat treatment (HT) of the inoculum (pH 6.2 or 7.5) produced greater hydrogen yields than low pH (6.2) conditions with a nonheat-treated inoculum (NHT). Conversion efficiencies of glucose to hydrogen (based on a theoretical yield of 4 mol-H 2 /mol-glucose) were as follows: 24.2% (HT, pH ) 6.2), 18.5% (HT, pH ) 7.5), 14.9% (NHT, pH ) 6.2), and 12.1% (NHT, pH ) 7.5). The main products of glucose (3 g-COD/L) utilization (g99%) in batch tests were acetate (3.4-24.1%), butyrate (6.4-29.4%), propionate (0.3-12.8%), ethanol (15.4-28.8%), and hydrogen (4.0-8.1%), with lesser amounts of acetone, propanol, and butanol (COD basis). Hydrogen gas phase concentrations in all batch cultures reached a maximum of 57-72% after 30 h but thereafter rapidly declined to nondetectable levels within 80 h. Separate experiments showed substantial hydrogen losses could occur via acetogenesis and that heat treatment did not prevent acetogenesis. Heat treatment consistently eliminated the production of measurable concentrations of methane. The disappearance of ethanol produced during hydrogen production was likely due to acetic acid production as thermodynamic calculations show that this reaction is spontaneous once hydrogen is depleted. Overall, these results show that low pH was, without heat treatment, sufficient to control hydrogen losses to methanogens in mixed batch cultures and suggest that methods will need to be found to limit acetogenesis in order to increase hydrogen gas yields by batch cultures.

- by Steven Van Ginkel
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- Environmental Science, Thermodynamics, Hydrogen, Heat Treatment

Solid-state fermentation (SSF) has built up credibility in recent years in biotech industries due to its potential applications in the production of biologically active secondary metabolites, apart from feed, fuel, food, industrial chemicals and pharmaceutical products and has emerged as an attractive alternative to submerged fermentation. Bioremediation, bioleaching, biopulping, biobeneficiation, etc. are the major applications of SSF in bioprocesses which have set another milestone. Utilization of agro-industrial residues as substrates in SSF processes provides an alternative avenue and value-addition to these otherwise under-or non-utilized residues. Innovation is the key to success and it is imperative to be up-to-date with the changing demands of the industries and meet their needs for better product and services. Better understanding of biochemical engineering aspects, particularly on mathematical modeling and design of bioreactors (fermenters) has made it possible to scale-up SSF processes and some designs have been developed for commercialization, making the technology economically feasible. In future, SSF technology would be well developed at par with SmF if rationalization and standardization continues in current trend. This review describes the state-of-art scenario in totality on SSF although the focus is on the most recent developments of last 5 years or so on SSF processes and products developments.

A laboratory procedure is described for measuring methane potentials of organic solid waste. Triplicate reactors with 10 grams of volatile solids were incubated at 55 C with 400 ml of inoculum from a thermophilic biogas plant and the methane production was followed over a 50-day period by regular measurements of methane on a gas chromatograph. The procedure involves blanks as well as cellulose controls. Methane potentials have been measured for source-separated organic household waste and for individual waste materials. The procedure has been evaluated regarding practicality, workload, detection limit, repeatability and reproducibility as well as quality control procedures. For the source-separated organic household waste a methane potential of 495 ml CH 4 /g VS was found. For fat and oil a lag-phase of several days was seen. The protein sample was clearly inhibited and the maximal methane potential was therefore not achieved. For paper bags, starch and glucose 63, 84 and 94% of the theoretical methane potential was achieved respectively. A detection limit of 72.5 ml CH 4 /g VS was calculated from the results. This is acceptable, since the methane potential of the tested waste materials was in the range of 200-500 ml CH 4 /g VS. The determination of methane potentials is a biological method subject to relatively large variation due to the use of non-standardized inoculum and waste heterogeneity. Therefore, procedures for addressing repeatability and reproducibility are suggested. #

- by Trine Hansen and +1
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- Environmental Engineering, Forecasting, Environmental Monitoring, Waste Management
- by Hosni Takache
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- Engineering, Technology, Photochemistry, Biotechnology

The overall goal of this work was to determine the effect of mixing the filter media of a compost biofilter on H 2 S removal efficiency. The behavior of important operational factors such as moisture of filter media, pressure drop and sulfate accumulation were evaluated, considering mixing the media. Additionally, tracer studies were performed in order to determine the effect of mixing the media on gas distribution. H 2 S removal capacity decreased over time, from 100% to 90%. When bed mixing was carried out, the removal capacity remained constant, close to 100%, and moisture content and sulfates accumulation were better controlled at 50% and at 12 mg S-SO 4 /g dry media respectively. In addition, under this operational pattern, an improvement in gas and particle size distribution was observed inside the filter media, fitting the axial dispersion model and the Ergun equation.

- by Adalberto Noyola
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- Chemistry, Medicine, Multidisciplinary, Ultrafiltration

Acid mine drainage (AMD) – characterized by high acidity and elevated sulfate and metal concentrations – represents a big environmental concern. Biological sulfate reduction has become an alternative to the classical physicochemical methods. In this study, domestic wastewater (DW) was tested as a cost-effective carbon-source for the remediation of AMD. Sediments from Tinto River, an extreme acidic environment with an elevated concentration of metals, were used as inoculum. Three anaerobic bioreactors with different microbial supports were fed with a 1:10 (v:v) mixture of synthetic AMD:DW. Around 50% of the organic matter present in the DW co-precipitated with the metals from the AMD previous to feeding the reactor. Therefore, the reactors had to be supplemented with an extra carbon-source (acetate) to achieve higher S elimination. Elevated removal efficiencies of chemical oxygen demand (COD) (>88%), sulfate (>75%), Fe (>85%) and other dissolved metals (>99% except for Mn...

The efficiency of ozone as a pre- and post-treatment to UASB treatment was investigated, followed by a study into UASB reactor performance with ozonated wastewater as substrate. Combinations of pre- and/or post-ozonation with UASB treatment gave better results than ozonation or UASB alone and COD reductions of 53.0-98.9% were achieved for treatment of canning and winery wastewaters. A UASB reactor was fed with pre-ozonated cannery wastewater for over 70 d. COD removal improved from between 58.8 and 64.4% to between 85.3 and 91.8% after pre-ozonated substrate feed commenced. Subsequent increases in organic loading rate (OLR) from 2.4 to 3.4 kgCOD m(-3) x d(-1) did not affect reactor performance. By including a final post-ozonation treatment to this UASB effluent a total COD reduction of 99.2% was achieved.

- by Gunnar Sigge
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- Water Purification, Multidisciplinary, Wine, South Africa
- by Samudra Prosad Banik
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- Organic Chemistry, Multivariate Analysis, cyclic AMP, Protein Secretion
- by Bibhash Nath
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- Biomass, Water Purification, Multidisciplinary, Seasonality

Hydrogen gas can be produced by electrohydrogenesis in microbial electrolysis cells (MECs) at greater yields than fermentation and at greater energy efficiencies than water electrolysis. It has been assumed that a membrane is needed in an MEC to avoid hydrogen losses due to bacterial consumption of the product gas. However, high cathodic hydrogen recoveries (78 ( 1% to 96 ( 1%) were achieved in an MEC despite the absence of a membrane between the electrodes (applied voltages of 0.3 < E ap < 0.8 V; 7.5 mS/cm solution conductivity). Through the use of a membrane-less system, a graphite fiber brush anode, and close electrode spacing, hydrogen production rates reached a maximum of 3.12 ( 0.02 m 3 H 2 /m 3 reactor per day (292 ( 1 A/m 3 ) at an applied voltage of E ap ) 0.8 V. This production rate is more than double that obtained in previous MEC studies. The energy efficiency relative to the electrical input decreased with applied voltage from 406 ( 6% (E ap ) 0.3 V) to 194 ( 2% (E ap ) 0.8 V). Overall energy efficiency relative to both E ap and energy of the substrate averaged 78 ( 4%, with a maximum of 86 ( 2% (1.02 ( 0.05 m 3 H 2 /m 3 day, E ap ) 0.4 V). At E ap ) 0.2 V, the hydrogen recovery substantially decreased, and methane concentrations increased from an average of 1.9 ( 1.3% (E ap ) 0.3-0.8 V) to 28 ( 0% of the gas, due to the long cycle time of the reactor. Increasing the solution conductivity to 20 mS/ cm increased hydrogen production rates for E ap ) 0.3-0.6 V, but consistent reactor performance could not be obtained in the high conductivity solution at E ap > 0.6 V. These results demonstrate that high hydrogen recovery and production rates are possible in a single chamber MEC without a membrane, potentially reducing the costs of these systems and allowing for new and simpler designs.

- by Sourav Sarkar
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- Water, Hydrogen, Electrochemistry, Bioenergy

Background: 1E10 monoclonal antibody is a murine anti-idiotypic antibody that mimics N-glycolyl-GM3 gangliosides. This antibody has been tested as an anti-idiotypic cancer vaccine, adjuvated in Al(OH) 3 , in several clinical trials for melanoma, breast, and lung cancer. During early clinical development this mAb was obtained in vivo from mice ascites fluid. Currently, the production process of 1E10 is being transferred from the in vivo to a bioreactor-based method.

- by Adolfo Castillo
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- Engineering, Thermodynamics, Organic Chemistry, Physical Chemistry

In this paper the production of laccase and the decolouration of the recalcitrant diazo dye Reactive Black 5 (RB5) by the white-rot fungus Trametes pubescens immobilised on stainless steel sponges in a fixed-bed reactor were studied. Laccase production was increased by 10-fold in the presence of RB5 and reached a maximum value of 1025 U/l. Enhanced laccase production in the presence of RB5 in this fungus is an added advantage during biodegradation of RB5-containing effluents. The decolouration of RB5 was due to two processes: dye adsorption onto the fungal mycelium and dye degradation by the laccase enzymes produced by the fungus. RB5 decolouration was performed during four successive batches obtaining high decolouration percentages (74%, 43% and 52% in 24 h for the first, third and four batch, respectively) without addition of redox mediators. Also, the in vitro decolouration of RB5 by the concentrated culture extract, containing mainly laccase, produced in the above bioreactor was studied. The decolouration percentages obtained were considerably lower (around 20% in 24 h) than that attained with the whole culture.

- by Susana Rodriguez-Couto
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- Engineering, Production, Adsorption, Biodegradation

A novel high-rate anaerobic reactor, called ''Buoyant Filter Bioreactor'' (BFBR), has been developed for treating lipid-rich complex wastewater. The BFBR is able to decouple the biomass and insoluble COD retention time from the hydraulic retention time by means of a granular filter bed made of buoyant polystyrene beads. Filter clogging is prevented by an automatic backwash driven by biogas release, which fluidizes the granular filter bed in a downward direction. During filter backwash, the solids captured in the filter are reintroduced into the reaction zone of the reactor. The reaction zone is provided with a mixing system, which is independent of the hydraulic retention time.

- by Ajit Haridas
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- Water, Filtration, Multidisciplinary, Lipids

Sunflower is a traditional crop which can be used for the production of bioenergy and liquid biofuels. A study of the pyrolytic behaviour of sunflower residues at temperatures from 300 to 600°C has been carried out. The experiments were performed in a captive sample reactor under atmospheric pressure and helium as sweeping gas. The yields of the derived pyrolysis products were determined in relation to temperature, with constant sweeping gas flow of 50 cm 3 min À1 and heating rate of 40°C s À1 . The maximum gas yield of around 53 wt.% was obtained at 500°C, whereas maximum oil yield of about 21 wt.% was obtained at 400°C. A simple first order kinetic model has been applied for the devolatilization of biomass. Kinetic constants have been estimated: E = 78.15 kJ mol À1 ; k 0 = 1.03 · 10 3 s À1 .

- by Efthymios Kantarelis
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- Kinetics, Multidisciplinary, Energy Metabolism, Greece

In this work, batch activated sludge studies were investigated for the treatment of raw pet food wastewater characterized by oil and grease concentrations of 50,000-66,000 mg/L, COD and BOD concentrations of 100,000 and 80,000 mg/L, respectively, as well as effluent from an existing anaerobic digester treating the aforementioned wastewater. A pre-treatment process, dissolved air flotation (DAF) achieved 97-99% reduction in O&G to about 400-800 mg/L, which is still atypically high for AS. The batch studies were conducted using a 4-L bioreactor at room temperature (21 • C) under different conditions. The experimental results showed for the DAF pretreated effluent, 92% COD removal efficiency can be achieved by using conventional activated sludge system at a 5 days contact time and applied initial soluble COD to biomass ratio of 1.17 mg COD/mg VSS. Similarly for the digester effluent at average oil and grease concentrations of 13,500 mg/L, activated sludge affected 63.7-76.2% soluble COD removal at 5 days. The results also showed that all kinetic data best conformed to the zero order biodegradation model with a low biomass specific maximum substrate utilization rate of 0.168 mg COD/mg VSS day reflecting the slow biodegradability of the wastewater even after 99% removal of oil and grease.

- by George Nakhla
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- Engineering, Kinetics, Biomass, Activated Sludge

In this study, non-woven MBR was used to treat hydrolysed biosolids wasted from a biological treatment plant. The concentration of SS of hydrolysed biosolids in influent was 10,000 mg/L and the concentration of SS in effluent was less than 200 mg/L with/without discharging wasted sludge depending on different HRTs, i.e. 20, 15 and 10 d. The results indicated that the percentage of biosolids reduction in terms of SS removal efficiency in non-woven MBR was around 65, 60 and 35%, respectively, depending on different HRTs. Meanwhile, the ratio of VSS/SS was decreased from 0.78 to 0.50 and the number of smaller inorganic particle sizes increased due to extended SRT. The initial flux in the non-woven MBR was set at 0.02, 0.04 and 0.06 m 3 /m 2 /day and trans-membrane pressure (TMP) was less than 10 kPa. The permeate flux could be maintained quite stably due to lower TMP. The proposed non-woven MBR could be used to achieve the reduction of biosolids in the wastewater treatment plant.

This study investigated the removal efficiency and mechanisms of water contaminants (mainly N-nitrosamines) during municipal wastewater reclamation by a membrane bioreactor (MBR) and nanofiltration (NF) hybrid system. The removal of bulk water contaminants was governed by the microbial activities in the MBR and molecular weight cut-off (MWCO) of the NF membranes. The removal of N-nitrosamines by the MBR was primarily attributed to biodegradation by aerobic bacteria, which can be determined by the reactivity of the amine functional groups with the catabolic enzymes (removal efficiency=45-84%). Adsorption and formation of membrane fouling can enhance the removal of N-nitrosamines by the NF membranes. However, size-exclusion is found to play a major role in the removal of N-nitrosamines by the NF membranes since the removal efficiencies of N-nitrosamines varied significantly depending on molecular weight of the N-nitrosamines and MWCO of the NF membranes (removal efficiency: NE90>NE...

- by Kangmin Chon
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- Water Purification, Nanoparticles, Multidisciplinary, Ultrafiltration

The biological treatment of ammonia-rich landfill leachates due to an inadequate C to N ratio requires expensive supplementation of carbon from an external carbon source. In an effort to reduce treatment costs, the objective of the study was to determine the feasibility of nitrogen removal via the nitrite pathway during landfill leachate co-treatment with municipal wastewater. Initially, the laboratory-scale sequencing batch reactor (SBR) was inoculated with nitrifying activated sludge and fed only raw municipal wastewater (RWW) during a start-up period of 9 weeks. Then, in the co-treatment period, consisting of the next 17 weeks, the system was fed a mixture of RWW and an increasing quantity of landfill leachates (from 1 to 10 % by volume). The results indicate that landfill leachate addition of up to 10 % (by volume) influenced the effluent quality, except for BOD 5. During the experiment, a positive correlation (r 2 =0.908) between ammonia load in the influent and nitrite in the effluent was observed, suggesting that the second step of nitrification was partially inhibited. The partial nitrification (PN) was also confirmed by fluorescence in situ hybridisation (FISH) analysis of nitrifying bacteria. Nitrogen removal via the nitrite pathway was observed when the oxygen concentration ranged from 0.5 to 1.5 mg O 2 /dm 3 and free ammonia (FA) ranged from 2.01 to 35.86 mg N-NH 3 / dm 3 in the aerobic phase. Increasing ammonia load in wastewater influent was also correlated with an increasing amount of total nitrogen (TN) in the effluent, which suggested insufficient amounts of assimilable organic carbon to complete denitrification. Because nitrogen removal via the nitrite pathway is beneficial for carbon-limited and highly ammonialoaded mixtures, obtaining PN can lead to a reduction in the external carbon source needed to support denitrification.

Membrane bioreactors (MBRs) for wastewater treatment offer the advantage of a complete removal of solids from the effluent. The secondary clarifier is replaced by a membrane filtration and therefore high biomass concentrations (MLSS) in the reactor are possible. The design of the aeration system is vital for an energy efficient operation of any wastewater treatment plant. Hence the exact measurement of oxygen transfer rates (OTR) and α-values is important. For MBRs these values reported in literature differ considerably. The OTR can be measured using non-steady state methods or using the off-gas method. The non-steady state methods additionally require the determination of the respiration rate (oxygen uptake rate ≡ OUR), which usually is measured in lab scale units. As there are differences of OUR between lab scale and full scale measurements, off-gas tests (which do not require an additional respiration test) were performed in order to compare both methods at high MLSS concentrations. Both methods result in the same average value of OTR. Due to variations in loading and wastewater composition variations of OTR in time can be pointed out using the off-gas method. For the first time a comparison of different oxygen transfer tests in full scale membrane bioreactors is presented.

Gasification of biomass produces a mixture of gas (mainly carbon monoxide (CO), carbon dioxide (CO 2), and hydrogen (H 2)) called synthesis gas, or syngas, by thermal degradation without combustion. Syngas can be used for heat or electricity production by thermochemical processes. This project aims at developing an alternative way to bioupgrade syngas into biogas (mainly methane), via anaerobic fermentation. Nonacclimated industrial granular sludge to be used as reactor inoculum was initially evaluated for mesophilic carboxydotrophic methanogenesis potential in batch tests at 4 and 8 mmol CO/g VSS.d, in the absence and presence of H 2 and CO 2 , respectively. Granular sludge was then introduced into a 30 L gas-lift reactor and supplied with CO, to study the production of methane and other metabolites, at different gas dilutions as well as feeding and recirculation rates. A maximal CO conversion efficiency of 75%, which was gas-liquid mass transfer limited, occurred at a CO partial pressure of 0.6 atm combined with a gas recirculation ratio of 20:1. The anaerobic granule potential for methanogenesis from CO was likely hydrogenotrophic, combined with CO-dependent H 2 formation, either under mesophilic or thermophilic conditions. Thermophilic conditions provide the anaerobic granules with a CO-bioconversion potential significantly larger (5-fold) than under mesophilic conditions, so long as the gas-liquid transfer is alleviated.

- by Serge Guiot
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- Biomass, Wastewater Treatment, Biogas, Multidisciplinary

Rice straw was treated with a mixed solution of acetic acid and propionic acid to enhance its biodegradability. The effect of acid concentration, pretreatment time, and the ratio of solid to liquid on the delignification performance of rice straw were investigated. It was found that the optimal conditions for hydrolysis were 0.75 mol/L acid concentration, 2 h pretreatment time and 1:20 solid to liquid ratio. Batch methane fermentation of untreated rice straw, pretreated rice straw, and the hydrolysates (the liquid fraction) of pretreatment were conducted at 35°C for 30 days, and the results indicated that methane production of rice straw can be enhanced by dilute organic acid pretreatment. Moreover, most of the acid in hydrolysates can also be converted into methane gas.

- by Zhongfang Lei
- •
- Scanning Electron Microscopy, Multidisciplinary, Cellulose, Propionic Acid

An integrated fluidized bed reactor (FBR) has been employed as the treatment for petrochemical industry wastewaters with high organic matter and aromatic compounds, under anaerobic and aerobic conditions. The system was operated at hydraulic residence time (HRT) of 2.7 and 2.2 h in the anaerobic and aerobic reactor, respectively. The degree of fluidization in the beds was 30%. This system showed a high performance on the removal of organic matter and aromatic compounds. At different organic loading rates (OLR), the chemical oxygen demand (COD) removal in the anaerobic reactor was close to 85% and removals of the COD up to 94% were obtained in the aerobic reactor. High removals of benzene, toluene, ethylbenzene, xylenes, styrene, 1,2,4-trimethylbenzene, 1,3,5-trimethylbenzene and naphthalene were achieved in this study.

- by Gabriela E . Moeller- Chávez
- •
- Biofilms, Petroleum, Water Purification, Multidisciplinary

Several wastes from agro-industrial activities were mixed in different ratios to evaluate the co-digestion process. Methane yield ðY CH 4 Þ, specific methanogenic activity (SMA) and a kinetic parameter (k 0) were determined. A second feeding was also performed to examine the recovery of bacterial activity after exhaustion. Mixture ratios of 1:1:1:1 and 1:3:4:0.5 (w/w) showed the best performance, with Y CH 4 of 664; 582 NmL CH 4 /gVS substrate , as well as SMA of 0.12; 0.13 gCOD NmLCH 4 =gVS inoculum =d, respectively, during the digestion of the first feed. It was possible to relate synergetic effects with enhancement in Y CH 4 by up to 43%, compared with values calculated from Y CH 4 of the individual substrates. All batches started up the biogas production after an exhaustion period, when a second feed was added. However, long lag phases (up to 21 days) were observed due to stressed conditions caused by the substrate limitation prior to the second feed.

- by Jhosane Pages Diaz
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- Production, Kinetics, Biotechnology, Evaluation
- by C. William Keevil
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- Biofilms, Biotechnology, Adolescent, Biological Sciences
- by Kee-yoeup Paek
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- Biotechnology, Biomass, Plant Roots, Bioreactors

MELiSSA is a bioregenerative life support system designed by the European Space Agency (ESA) for the complete recycling of gas, liquid and solid wastes during long distance space exploration. The system uses the combined activity of different living organisms: microbial cultures in bioreactors, a plant compartment and a human crew. In this minireview, the development of a short-cut ecological system for the biotransformation of organic waste is discussed from a microorganism’s perspective. The artificial ecological model—still in full development—that is inspired by Earth’s own geomicrobiological ecosystem serves as an ideal study object on microbial ecology and will become an indispensable travel
companion in manned space exploration.

- by Paul Janssen
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- Microbiology, Environmental microbiology, Microbial Ecology, Medical Microbiology
- by Debarati Paul
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- Microbiology, Biofilms, Medical Microbiology, Bacteria

To be able to predict the degradation (rate) of organic chemicals (e.g. pesticides) in the ®eld, knowledge of the environmental conditions that are of in¯uence on the degradation process are of importance. In the present study an experimental system is described which is used to study the degradation of organic pollutants in mixed bacteria cultures originating from surface water. With this system the degradation of compounds can be followed for relatively long experimental periods (months). In addition, it is possible to vary dierent environmental parameters in order to investigate their in¯uences on the degradation of the chemical. These preliminary experiments show that growth and ÔcompositionÕ of the bacteria culture have comparable patterns in parallel experiments. The ®rst order degradation rate constant for the test compound dichloran, as calculated from these experiments under these circumstances, is about 0.002 h À1 . Ó

- by Marca Schrap
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- Multidisciplinary, Pesticides, Bacteria, Fresh water

The present study describes citric acid fermentation by Aspergillus niger GCB-47 in a 15-l stainless steel stirred fermentor. Among the alcohols tested as stimulating agents, 1.0% (v/v) methanol was found to give maximum amount of anhydrous citric acid (90:02 AE 2:2 g/l), 24 h after inoculation. This yield of citric acid was 1.96 fold higher than the control. Methanol has a direct effect on mycelial morphology and it promotes pellet formation. It also increases the cell membrane permeability to provoke more citric acid excretion from the mycelial cells. The sugar consumed and % citric acid was 108 AE 3:8 g/l and 80:39 AE 4:5%, respectively. The desirable mycelial morphology was in the form of small round pellets having dry cell mass 14:5 AE 0:8 g/l. Addition of ethanol, however, did not found to enhance citric acid production, significantly. The maximum value of Y p=x (i.e., 5:825 AE 0:25 g/g) was observed when methanol was used as a stimulating agent. The best results of anhydrous citric acid were observed, 6 days after inoculation when the initial pH of fermentation medium was kept at 6.0.

- by sikander ali
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- Multidisciplinary, Methanol, Ethanol, Stainless Steel

A microchip-based cell culture system was developed and a primary culture of rat hepatocytes was realized in the system. The microchip was made of glass plates and had a microchannel and a microculture flask inside. The flask inner surface was coated using collagen solution; then FBS and DMEM were added successively. Rat hepatocytes suspended in a medium was introduced into the microchip and incubated at 37 • C in a humidified atmosphere with 5% CO 2 . Because of the shortage of dissolved oxygen, the cultured cells in the microchip resulted in a significant decrease in viability. To overcome this, a continuous medium flow oxygen and nutrition supplying system was designed and constructed. The system realized good cell growth for at least 4 days. Liver-specific functions, such as the synthesis of albumin and urea from hepatocytes were confirmed.

- by Masayuki Yamato
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- Engineering, Technology, Cell Culture, Urea

A new-type in situ probe has been developed to acquire dark field images of yeast in bioreactors. It has been derived from an in situ bright field microscope that is able to measure cell density in bioreactors during fermentation processes. The illumination part of the probe has been replaced with a dark field device, in which an aspheric condenser is used, so that high contrast dark field images can be obtained. The technique of second imaging is implemented to improve the sharpness of the images by means of a relay lens. This new in situ probe is expected to enable the evaluation of the cell viability without staining owing to modern image processing.

- by Tim Dark
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- Engineering, Technology, Image Processing, Microscopy

Aims: The present investigation deals with the development of thermotolerant mutant strain of yeast for studying enhanced productivity of ethanol from molasses in a fully controlled bioreactor. Methods and Results: The parental culture of Saccharomyces cerevisiae ATCC 26602 was mutated using UV treatment. A single thermotolerant mutant was isolated after extensive screening and optimization, and grown on molasses medium in liquid cultures. The mutant was 1AE45-fold improved than its wild parent with respect to ethanol productivity (7AE2 g l )1 h )1 ), product yield (0AE44 g ethanol g )1 substrate utilized) and specific ethanol yield (19AE0 g ethanol g )1 cells). The improved ethanol productivity was directly correlated with titres of intracellular and extracellular invertase activities. The mutant supported higher volumetric and product yield of ethanol, significantly (P £ 0AE05) higher than the parental and other strains. The mutated cultures produced 1AE8-and 2AE6-fold more extracellular and intracellular invertase productivity, respectively, than that produced by its wild parent at 40°C. Thermodynamic studies revealed that the cell system exerted protection against thermal inactivation during formation of products. Conclusions: A mutant derivative of Sacchromyces cerevisiae with improved productivity of ethanol and invertases has been obtained, which showed concomitant improvement in thermostability of endogenous metabolism for formation of both ethanol and invertases. Significance and Impact of the Study: The results of the present study are of commercial value as the mutant can be used for ethanol production in parts of Pakistan where the temperature may go up to 40°C in April. Ethanol product yield coefficient and volumetric productivity, revealed the hyper-productivity of ethanol from molasses at 40°C, which is not appropriate for wild organism.

- by Muhammad Ferhan
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- Thermodynamics, Kinetics, Multidisciplinary, Entropy
- by Ajit Dash
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- Cancer, Fluorescence Microscopy, Endothelial Cells, Perfusion

The aim of this study was to evaluate the removal of linear alkylbenzene sulfonate (LAS) in an anaerobic fluidized bed reactor (AFBR) treating wastewater containing soap powder as LAS source. At Stage I, the AFBR was fed with a synthetic substrate containing yeast extract and ethanol as carbon sources, and without LAS; at Stage II, soap powder was added to this synthetic substrate obtaining an LAS concentration of 14 ± 3 mg L(-1). The compounds of soap powder probably inhibited some groups of microorganisms, increasing the concentration of volatile fatty acids (VFA) from 91 to 143 mg HAc L(-1). Consequently, the LAS removal rate was 48 ± 10% after the 156 days of operation. By sequencing, 16S rRNA clones belonging to the phyla Proteobacteria and Synergistetes were identified in the samples taken at the end of the experiment, with a remarkable presence of Dechloromonas sp. and Geobacter sp.

- by Dagoberto Y Okada and +1
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- Water Purification, Multidisciplinary, Phylogeny, Time Factors

A key parameter for understanding and controling the anaerobic biogas process is the concentration of volatile fatty acids (VFA). However, this information has so far been limited to off-line measurements using labor-intensive methods. We have developed a new technique that has made it possible to monitor VFA online in one of the most difficult media: animal slurry or manure. A novel in situ filtration technique has made it possible to perform microfiltration inside a reactor system. This filter enables sampling from closed reactor systems without large-scale pumping and filters. Furthermore, due to its small size it can be placed in lab-scale reactors without disturbing the process. Using this filtration technique together with commercially available membrane filters we have constructed a VFA sensor system that can perform automatic analysis of animal slurry at a frequency as high as every 15 minutes. Reproducibility and recovery factors of the entire system have been determined. The VFA sensor has been tested for a period of more than 60 days with more than 1000 samples on both a full-scale biogas plant and lab-scale reactors. The measuring range covers specific measurements of acetate, propionate, iso-/n-butyrate and iso-/n-valerate ranging from 0.1 to 50 mM (6-3000 mg). The measuring range could readily be expanded to more components and both lower and higher concentrations if desired. In addition to the new VFA sensor system, test results from development and testing of the in situ filtration technique are being presented is this article.

- by Birgitte Ahring
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- Multidisciplinary, Ultrafiltration, Transducers, Temperature
- by Frédérique Balandras and +1
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- Engineering, Technology, Biotechnology, Cell Division

Distribution and occurrence of Archaea and methanogenic activity in a laboratory scale, completely mixed anaerobic reactor treating pharmaceutical wastewaters were investigated and associated with reactor performance. The reactor was initially seeded with anaerobic digester sludge from an alcohol distillery wastewater treatment plant and was subjected to a three step feeding strategy. The feeding procedure involved gradual transition from a glucose containing feed to a solvent stripped pharmaceutical wastewater and then raw pharmaceutical wastewater. During the start-up period, over 90% COD removal efficiency at an organic loading rate (OLR) of 6 kg COD m À3 d À1 was achieved with glucose feeding, and acetoclastic methanogenic activity was 336 ml CH 4 gTVS À1 d À1 . At the end of the primary loading, when the feed contained solvent stripped pharmaceutical wastewater at full composition, 71% soluble COD removal efficiency was obtained and acetoclastic methanogenic activity decreased to half of the rate under glucose feed (166 ml CH 4 gTVS À1 d À1 ). At the end of secondary loading with 60% (w/v) raw pharmaceutical wastewater, COD removal dropped to zero and acetoclastic methanogenic activity fell to less than 10 ml CH 4 gTVS À1 d À1 . Throughout the course of the experiment, microbial community structure was monitored by DGGE analysis of 16S rRNA gene fragments. Five different archaeal taxa were identified and the predominant archaeal sequences belonged to methanogenic Archaea. Two of these showed greatest sequence identity with Methanobacterium formicicum and Methanosaeta concilii. The types of Archaea present changed little in response to changing feed composition but the relative contribution of different organisms identified in the archaeal DGGE profiles did change. r

- by Orhan Ince and +1
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- Water, Population Dynamics, Multidisciplinary, Anaerobic Digestion

During the last decade, several screening programs for pharmaceuticals at Swedish wastewater treatment plants (WWTPs) have been conducted by research institutes, county councils, and wastewater treatment companies. In this study, influent and effluent concentrations compiled from these screening programs were used to assess the occurrence and reduction of non-antibiotic pharmaceuticals for human usage. The study is limited to full-scale WWTPs with biological treatment.

- by Henrik R Andersen
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- Environmental Monitoring, Filtration, Multidisciplinary, Sweden
- by Adriano Henriques
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- Engineering, Technology, Biotechnology, Biological Sciences

The CCU and Incubator are habitats under development by SSBRP for gravitational biology research on ISS. They will accommodate multiple specimen types and reside in either Habitat Holding Racks, or the Centrifuge Rotor, which provides selectable gravity levels of up to 2 g. The CCU can support multiple Cell Specimen Chambers, CSCs (18, 9 or 6 CSCs; 3, 10 or 30 mL in volume, respectively). CSCs are temperature controlled from 4-39 degrees C, with heat shock to 45 degrees C. CCU provides automated nutrient supply, magnetic stirring, pH/O2 monitoring, gas supply, specimen lighting, and video microscopy. Sixty sample containers holding up to 2 mL each, stored at 4-39 degrees C, are available for automated cell sampling, subculture, and injection of additives and fixatives. CSCs, sample containers, and fresh/spent media bags are crew-replaceable for long-term experiments. The Incubator provides a 4-45 degrees C controlled environment for life science experiments or storage of experimenta...

- by Melissa Kirven-Brooks
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- Video microscopy, Space flight, Automation, Hypergravity
- by Serena Fonda
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- Microbiology, Environmental Science, Carbon, Biotechnology

Laccase from Trametes versicolor was immobilized by diazotization on a nylon membrane grafted with glycidil methacrylate, using phenylenediamine as spacer and coupling agent. The behavior of these enzyme derivatives was studied under isothermal and nonisothermal conditions by using syringic acid as substrate, in view of the employment of these membranes in processes of detoxification of vegetation waters from olive oil mills. The pH and temperature dependence of catalytic activity under isothermal conditions has shown that these membranes can be usefully employed under extreme pH and temperatures. When employed under nonisothermal conditions, the membranes exhibited an increase of catalytic activity linearly proportional to the applied transmembrane temperature difference. Percentage activity increases ranging from 62% to 18% were found in the range of syringic acid concentration from 0.02 to 0.8 mM, when a difference of 1°C was applied across the catalytic membrane. Because the percentage activity increase is strictly related to the reduction of the production times, the technology of nonisothermal bioreactors has been demonstrated to be an useful tool also in the treatment of vegetation waters from olive oil mills.

- by D Mita
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- Engineering, Technology, Catalysis, Biotechnology

A circulating loop bioreactor (CLB) with cells immobilized in loofa sponge was constructed for simultaneous aerobic and anaerobic processes. The CLB consists of an aerated riser and a non-aerated downcomer column connected at the top and bottom by cylindrical pipes. Ethanol production from raw cassava starch was investigated in the CLB. Aspergillus awamori IAM 2389 and Saccharomyces cerevisiae IR2 immobilized on loofa sponge were placed, respectively, in the aerated riser column and non-aerated downcomer column. Both aamylase and glucoamylase activities increased as the aeration rate was increased. Ethanol yield and productivity increased with an increase in the aeration rate up to 0.5 vvm, but decreased at higher aeration rates. The CLB was operated at an aeration rate of 0.5 vvm for more than 600 h, resulting in an average ethanol productivity and yield from raw cassava starch of 0.5 g-ethanol l-1 h-1 and 0.45 g ethanol/g starch, respectively. In order to increase ethanol productivity, it was necessary to increase the dissolved oxygen (DO) concentration in the riser column and decrease the DO concentration in the downcomer column. However, increasing the aeration rate resulted in increases in the DO concentration in both the riser and the downcomer columns. At high aeration rate, there was no significant difference in the DO concentration in the riser and downcomer columns. The aeration rate was therefore uncoupled from the liquid circulation by attaching a timecontrolled valve in the upper connecting pipe. By optimizing the time and frequency of valve opening, and operation at high aeration rate, it was possible to maintain a very high DO concentration in the riser column and a low DO concentration in the downcomer column. Under these conditions, ethanol productivity increased by more than 100%, to 1.17 g l-1 h-1 .

- by Noel Roble
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- Chemistry, Productivity, Starch, Medicine

Huge efforts have been made both in adopting more environmental-friendly bleaching processes, and in developing advanced oxidation processes and more effective biological treatments for the reduction of deleterious impacts of paper mill effluents. Even so, the success of such treatments is frequently reported in terms of chemical parameters without a proper evaluation of the effluent's toxicity mitigation. This is the first study reporting an exhaustive evaluation of the toxicity of a secondary bleached kraft pulp mill effluent, after either tertiary treatment with the soft-rot fungi Rhizopus oryzae or with a photo-Fenton oxidation, using a battery of freshwater species. As it has been reported the photo-Fenton/ UV treatment has proved to be the most effective in reducing the colour and the COD (chemical oxygen demand) of the effluent. Nevertheless, extremely low EC 50 values were reported for almost all species, after this tertiary treatment. The treatment with R. oryzae was less effective in terms of colour removal and COD reduction, but proved to be the most promising in reducing toxicity.

- by Isa Peres
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- Water, Daphnia, Multidisciplinary, Color

In this study, the endogenous respiration rate and the observed biomass yield of denitrifying methylotrophic biomass were estimated through measuring changes in denitrification rates (DNR) as a result of maintaining the biomass under methanol deprived conditions. For this purpose, activated sludge biomass from a full-scale wastewater treatment plant was kept in 10-L batch reactors for 8 days under fully aerobic and anoxic conditions at 20 °C without methanol addition. To investigate temperature effects, another biomass sample was placed under starvation conditions over a period of 10 days under aerobic conditions at 25 °C. A series of secondary batch tests were conducted to measure DNR and observed biomass yields. The decline in DNR over the starvation period was used as a surrogate to biomass decay rate in order to infer the endogenous respiration rates of the methylotrophs. The regression analysis on the declining DNR data shows 95% confidence intervals of 0.130 ± 0.017 day−1 for ...

- by ahmed al-omari
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- Biomass, Biology, Medicine, Multidisciplinary
- by Maciej Sobczyński
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- Microbiology, Escherichia coli, Amino Acids, Bioreactors