Showing papers on "Bioreactor published in 2009"

Scale-up analysis for a CHO cell culture process in large-scale bioreactors.

Abstract: Bioprocess scale-up is a fundamental component of process development in the biotechnology industry. When scaling up a mammalian cell culture process, it is important to consider factors such as mixing time, oxygen transfer, and carbon dioxide removal. In this study, cell-free mixing studies were performed in production scale 5,000-L bioreactors to evaluate scale-up issues. Using the current bioreactor configuration, the 5,000-L bioreactor had a lower oxygen transfer coefficient, longer mixing time, and lower carbon dioxide removal rate than that was observed in bench scale 5- and 20-L bioreactors. The oxygen transfer threshold analysis indicates that the current 5,000-L configuration can only support a maximum viable cell density of 7 x 10(6) cells mL(-1). Moreover, experiments using a dual probe technique demonstrated that pH and dissolved oxygen gradients may exist in 5,000-L bioreactors using the current configuration. Empirical equations were developed to predict mixing time, oxygen transfer coefficient, and carbon dioxide removal rate under different mixing-related engineering parameters in the 5,000-L bioreactors. These equations indicate that increasing bottom air sparging rate is more efficient than increasing power input in improving oxygen transfer and carbon dioxide removal. Furthermore, as the liquid volume increases in a production bioreactor operated in fed-batch mode, bulk mixing becomes a challenge. The mixing studies suggest that the engineering parameters related to bulk mixing and carbon dioxide removal in the 5,000-L bioreactors may need optimizing to mitigate the risk of different performance upon process scale-up.

Exploiting olive oil mill effluents as a renewable resource for production of biodegradable polymers through a combined anaerobic-aerobic process

Abstract: BACKGROUND: The performance of a three-stage process for polyhydroxyalkanoate (PHA) bioproduction from olive oil mill effluents (OME) has been investigated. In the first anaerobic stage OME were fermented in a packed bed biofilm reactor into volatile fatty acids (VFAs). This VFA-rich effluent was fed to the second stage, operated in an aerobic sequencing batch reactor (SBR), to enrich mixed cultures able to store PHAs. Finally, the storage response of the selected consortia was exploited in the third aerobic stage, operated in batch conditions. RESULTS: The anaerobic stage increased the VFA percentage in the OME from 18% to ∼32% of the overall chemical oxygen demand (COD). A biomass with high storage response was successfully enriched in the SBR fed with the fermented OME at an organic load rate of 8.5 gCOD L−1 d−1, with maximum storage rate and yield (146 mgCOD gCOD−1 h−1 and 0.36 COD COD−1, respectively) very similar to those obtained with a synthetic VFA mixture. By means of denaturing gradient gel electrophoresis (DGGE) analysis, different bacterial strains were identified during the two SBR runs: Lampropedia hyalina and Candidatus Meganema perideroedes, with the synthetic feed or the fermented OMEs, respectively. In the third stage, operated at increasing loads, the maximum concentration of the PHA produced increased linearly with the substrate fed. Moreover, about half of the stored PHAs were produced from substrates other than VFAs, mostly alcohols. CONCLUSION: The results obtained indicate that the process is effective for simultaneous treatment of OME and their valorization as a renewable resource for PHA production. Copyright © 2009 Society of Chemical Industry

Twenty-four well plate miniature bioreactor system as a scale-down model for cell culture process development.

Abstract: Increasing the throughput and efficiency of cell culture process development has become increasingly important to rapidly screen and optimize cell culture media and process parameters. This study describes the application of a miniaturized bioreactor system as a scaled-down model for cell culture process development using a CHO cell line expressing a recombinant protein. The microbioreactor system (M24) provides non-invasive online monitoring and control capability for process parameters such as pH, dissolved oxygen (DO), and temperature at the individual well level. A systematic evaluation of the M24 for cell culture process applications was successfully completed. Several challenges were initially identified. These included uneven gas distribution in the wells due to system design and lot to lot variability, foaming issues caused by sparging required for active DO control, and pH control limitation under conditions of minimal dissolved CO2. A high degree of variability was found which was addressed by changes in the system design. The foaming issue was resolved by addition of anti-foam, reduction of sparge rate, and elimination of DO control. The pH control limitation was overcome by a single manual liquid base addition. Intra-well reproducibility, as indicated by measurements of process parameters, cell growth, metabolite profiles, protein titer, protein quality, and scale-equivalency between the M24 and 2 L bioreactor cultures were very good. This evaluation has shown feasibility of utilizing the M24 as a scale-down tool for cell culture application development under industrially relevant process conditions.

Techniques for oxygen transfer measurement in bioreactors: a review

Abstract: Oxygen is the most essential requirement for aerobic bioprocesses. The microbial growth in a bioreactor depends upon the oxygen transfer rate (OTR). The OTR is widely used to study the growth behavior of microbial and plant cell cultures. The mass transfercoefficient(kLa)determinesthemagnitudeoftheOTR.Therearemanytechniquesformeasuringoxygenconcentration andOTRinbioreactors.Zirconia,electrochemical,infrared,ultrasonicandlasercellsareusedtomeasureoxygenconcentration in the liquid medium. Optical sensors are better alternatives to measure oxygen concentration in small bioreactors. Sulfite oxidation and gassing-out methods with a Clark-type electrode have been used for OTR measurements in bioreactors. Many new novel techniques have evolved recently for intermittent and continuous online measurement of OTR/kLa in various types ofbioreactors.Thepresentpapergivesanoverviewofvariousmeasurementtechniquesandtheirlimitationsand/orsuitability for measurementof OTR/kLa in various kinds of bioreactors, especially small bioreactors. c � 2009 Society of Chemical Industry

Bag bioreactor based on wave-induced motion: characteristics and applications.

Abstract: Today wave-mixed bag bioreactors are common devices in modern biotechnological processes where simple, safe and flexible production has top priority. Numerous studies that have been published on ex vivo generation of cells, viruses and therapeutic agents during the last 10 years have confirmed their suitability and even superiority to stirred bioreactors made from glass or stainless steel for animal as well as plant cell cultivations. In these studies the wave-mixed bag bioreactors enabled middle to high cell density and adequate productivity in laboratory and pilot scale. This mainly results from low-shear conditions and highly efficient oxygen transfer for cell cultures, as demonstrated for the widely used BioWave®.Starting with an overview of wave-mixed bag bioreactors and their common operation strategies, this chapter delineates engineering aspects of BioWave®, which like Wave Reactor™ and BIOSTAT®CultiBag RM originates from the prototype of a wave-mixed bag bioreactor introduced in 1998. Subsequently, the second part of the chapter focuses on reported BioWave® applications. Conditions and results from cultivations with animal cells, plant cells, microbial cells and nematodes are presented and discussed.

Pilot scale hybrid process for olive mill wastewater treatment and reuse

Abstract: A novel process has been developed at pilot scale for the treatment of olive mill wastewater (OMW), which combines electro-Fenton, anaerobic digestion and ultrafiltration. Application of electro-Fenton procedure in semi-continuous mode permitted high removal efficiencies of chemical oxygen demand (COD) (50%) and monophenolic compounds (95%). This pre-treatment was found to enhance the anaerobic activity of an up-flow anaerobic filter (300 l) significantly. In the bioreactor, COD removal efficiency of 75% was reached at a hydraulic retention time of 4.5 d and an organic loading rate of 10 g COD l −1 d −1 . The use of ultrafiltration technology as a post-treatment completely detoxified the anaerobic effluent and removed its high molecular mass polyphenols. An economic calculation of this treatment process revealed that a surplus of energy of 73.5 kWh could be recovered after the treatment of 1 m 3 .

Anaerobic Biodegradation Tests of Poly(lactic acid) under Mesophilic and Thermophilic Conditions Using a New Evaluation System for Methane Fermentation in Anaerobic Sludge

Abstract: Anaerobic biodegradation tests of poly(lactic acid) (PLA) powder were done at the thermophilic (55 °C) and mesophilic temperature (35 °C) under aquatic conditions [total solid concentrations of the used sludge were 2.07% (at 55 °C) and 2.24% (at 35 °C)] using a newly developed evaluation system. With this system, the evolved biogas is collected in a gas sampling bag at atmospheric pressure. This method is more convenient than using a pressure transducer or inverted graduated cylinder submerged in water. PLA was degraded about 60% in 30 days, about 80% in 40 days and about 90% in 60 days at 55 °C. On the other hand, the PLA degradation started in 55 days at 35 °C and degradation rate was much slower than at 55 °C.

Characterization of a biofilm membrane reactor and its prospects for fine chemical synthesis.

Abstract: Biofilms are known to be robust biocatalysts. Conventionally, they have been mainly applied for wastewater treatment, however recent reports about their employment for chemical synthesis are increasingly attracting attention. Engineered Pseudomonas sp. strain VLB120ΔC biofilm growing in a tubular membrane reactor was utilized for the continuous production of (S)-styrene oxide. A biofilm specific morphotype appeared in the effluent during cultivation, accounting for 60–80% of the total biofilm irrespective of inoculation conditions but with similar specific activities as the original morphotype. Mass transfer of the substrate styrene and the product styrene oxide was found to be dependent on the flow rate but was not limiting the epoxidation rate. Oxygen was identified as one of the main parameters influencing the biotransformation rate. Productivity was linearly dependent on the specific membrane area and on the tube wall thickness. On average volumetric productivities of 24 g L day−1 with a maximum of 70 g L day−1 and biomass concentrations of 45 gBDW L have been achieved over long continuous process periods (≥50 days) without reactor downtimes. Biotechnol. Bioeng. 2010. 105: 705–717. © 2009 Wiley Periodicals, Inc.

Experimental Study and Design of a Submerged Membrane Distillation Bioreactor

Abstract: A hybrid process incorporating membrane distillation in a submerged membrane bioreactor operated at elevated temperature is developed and experimentally demonstrated in this article. Since organic particles are rejected by an ‘evaporation’ mechanism, the retention time of non-volatile soluble and small organics in the submerged membrane distillation bioreactor (MDBR) is independent of the hydraulic retention time (mainly water and volatiles). A high permeate quality can be obtained in the one-step compact process. The submerged MD modules were designed for both flat-sheet membranes and tubular membrane configurations. The process performance was preliminarily evaluated by the permeate flux stabilities. The module configuration design and air sparging used in the MDBR process were tested. Flux declines were observed for the thin flat-sheet hydrophobic membranes. Tubular membrane modules provided more stable permeate fluxes probably due to the turbulent condition generated from air sparging injected inside the tubular membrane bundles. The experiments with the submerged tubular MD module gave stable fluxes of approximately 5 L/m2 h over 2 weeks at a bioreactor temperature of 56 °C. The total organic carbon in the permeate was consistently lower than 0.7 mg/L for all experiments.

Occurrence, Source, and Fate of Dissolved Organic Matter (DOM) in a Pilot-Scale Membrane Bioreactor

Abstract: In this study, the fate of carbohydrates, proteins, and humic substances in feedwater, sludge supernatant, and permeate of a pilot-scale membrane bioreactor (MBR) was investigated. Over 10 months, ...

Fast dynamic response of the fermentative metabolism of Escherichia coli to aerobic and anaerobic glucose pulses.

Abstract: The response of Escherichia coli cells to transient exposure (step increase) in substrate concentration and anaerobiosis leading to mixed-acid fermentation metabolism was studied in a two-compartment bioreactor system consisting of a stirred tank reactor (STR) connected to a mini-plug-flow reactor (PFR: BioScope, 3.5 mL volume). Such a system can mimic the situation often encountered in large-scale, fed-batch bioreactors. The STR represented the zones of a large-scale bioreactor that are far from the point of substrate addition and that can be considered as glucose limited, whereas the PFR simulated the region close to the point of substrate addition, where glucose concentration is much higher than in the rest of the bioreactor. In addition, oxygen-poor and glucose-rich regions can occur in large-scale bioreactors. The response of E. coli to these large-scale conditions was simulated by continuously pumping E. coli cells from a well stirred, glucose limited, aerated chemostat (D = 0.1 h−1) into the mini-PFR. A glucose pulse was added at the entrance of the PFR. In the PFR, a total of 11 samples were taken in a time frame of 92 s. In one case aerobicity in the PFR was maintained in order to evaluate the effects of glucose overflow independently of oxygen limitation. Accumulation of acetate and formate was detected after E. coli cells had been exposed for only 2 s to the glucose-rich (aerobic) region in the PFR. In the other case, the glucose pulse was also combined with anaerobiosis in the PFR. Glucose overflow combined with anaerobiosis caused the accumulation of formate, acetate, lactate, ethanol, and succinate, which were also detected as soon as 2 s after of exposure of E. coli cells to the glucose and O2 gradients. This approach (STR-mini-PFR) is useful for a better understanding of the fast dynamic phenomena occurring in large-scale bioreactors and for the design of modified strains with an improved behavior under large-scale conditions. Biotechnol. Bioeng. 2009; 104: 1153–1161. © 2009 Wiley Periodicals, Inc.