Papers by Keyword: Bioreactor

Abstract: In this article, we are interested in identifying the parameters of an aerobic bioprocess modelused for wastewater treatment. In the field of biotechnology, various computer bugs caused by roundingerrors can induce an error interval that is too wide during data acquisition. For this reason, weare testing a new identification method using a set method based on interval arithmetic. The processstudied is the chemical transformation of ammoniacal nitrogen which takes place in two stages: Reactionof nitrificationdenitrification.The parameters chosen for the identification are the yields andthe maximum growth rates. Initially, the study of observability by a differential algebraic method willsimplify the study of the mathematical model. This nonlinear model is described by six differentialequations. Subsequently, we apply a set method, in particular the propagation of constraints also calledforwardbackward propagation, this technique allowed us to determine intervals containing the variablereturns as well as the maximum specific growth rates defined from the Monod model which describesthe operation of the bioreactor. This method also guarantees the result by rejecting all inconsistentvalues.

Abstract: In this study, Computational Fluid Dynamics (CFD), applied to a non-Newtonian fluid, was developed to characterize gas-liquid interaction and mixing process in a 15 m³ (working volume) bioreactor. The bioreactor was equipped with four arrangements of standard Rushton, Pitch-blade and Scaba® impellers. Gas-liquid hydrodynamics was estimated based on CFD results. The chosen operating conditions were defined by the settings used for production of xanthan gum via fermentation route by Xanthomonas campestris. The mixing process was simulated by using the k-epsilon turbulence model, Multiple Reference Frame and Population Balance Model approaches. The simulation results have been compared and analyzed by isosurfaces, volume fractions, velocity graphs, torques and flow analysis calculations. Obtained results revealed that for the Pitched-Pitched-Pitched arrangement to avoid the constraint-imposed overload torque limitations impeller diameter size should be reduced by 10%. The use of Rushton-Rushton-Rushton impeller arrangement was discouraged for non-Newtonian pseudoplastic fluid mixing, whereas Pitched-Rushton-Scaba and Scaba-Rushton-Pitched impeller arrangements were both acceptable.

Abstract: We review here the current research status on bioreactors for tissue engineering with cell electrical stimulation. Depending on the cell types, electrical stimulation has distinct objectives, in particular being employed both to mimic and enhance the endogenous electricity measured in the natural regeneration of living organisms as well as to mimic strain working conditions for contractible tissues (for instance muscle and cardiac tissues). Understanding the distinct parameters involved in electrical stimulation is crucial to optimize its application. The results presented in the literature and reviewed here reveal that the application of electrical stimulation can be essential for tissue engineering applications.

Abstract: This research addresses the challenges of sustainable use of natural polymers, including in technical fields. One of the leading trends in science and industry headway today lies in designing advanced functional materials, e.g. for manufacturing medical items, technical devices, food-processing tools et al. For this purpose, universally applicable technological processes are being developed, including in biotechnology. One of the main goals of this research is to explore ways to consolidate living systems, by instilling in them desirable physical and chemical properties so as to diversify their applications, including in technical fields. Polymers structure and properties have been investigated via raster electron microscopy, spectral analysis, et al.

Abstract: Using microorganisms to mediate crystallisation of metals and minerals in open-culture bioreactors has potential to recover recyclable materials from dilute aqueous streams, but also to prevent their emission to the environment. Although this potential is already exploited in practice to some extent, biological crystallization for metal recovery is still largely a black box technology with limited understanding of the role of the microorganisms in the crystallization, and the differences with chemical crystallisation. Using biocrystallisation of scorodite (FeAsO₄.2H₂O) and sphalerite (ZnS) as examples we propose that the role of microorganisms strongly depends on established saturation state of the solution. For scorodite, microorganisms are used to exert control over the crystallization as their ferrous iron-oxidizing activity keeps the solution slightly oversaturated. Also, the oversaturation level is kept homogeneous because of continuous biological formation of the reactant ferrous iron throughout the solution. In continuous bioreactor experiments on which we reported previously, scorodite crystal sizes still increased after 72 days of bioreactor operation indicating that indeed crystal growth was favored over nucleation. On the other hand, in our experiments with zinc sulfide, crystallization proceeded in highly oversaturated solutions in a continuous sulfate reducing bioreactor fed with a zinc sulfate solution and H₂/CO₂ as electron donor and carbon source. The high oversaturation likely resulted in dominant primary nucleation in the bulk solution, with little or no control over crystal growth, even though agglomeration may still have occurred. This was exemplified by particle sizes which decreased in the bioreactor experiment and remained stable after already about 2 weeks of operation.

Abstract: The objective of this study is to improve the understanding of copper sulfides dissolution and to use this knowledge for optimization of process parameters for commercial application of electrochemical bioleaching of chalcopyrite concentrates in stirred bioreactors. From the results of this study, the importance of the oxidation reduction potential (ORP) on the catalytic interaction between chalcopyrite and pyrite can be pointed out as the main parameters for successful bioprocessing of chalcopyrite concentrates. Under these conditions, the optimization of the average particle size of feed (D80) and adjusting the ORP in the range between 400-450 mV are important criteria for increasing the electrochemical bioleaching rate of chalcopyrite concentrates. It seems that the main reason for the increased copper recovery could be the control and prevention of chalcopyrite passivation resulting from improved galvanic interaction between copper sulfide minerals, here especially chalcopyrite and pyrite in the selected ORP range and the right particle size distribution of feed. At optimum conditions, the copper extraction from chalcopyrite flotation concentrate during 7 days of continuous electrochemical bioleaching operations in stirred tanks was about 95%, which should be high enough to justify the process economically.

Abstract: Detailed descriptions of the consortia present in commercial mineral processing operations have emerged in recent years, improving our understanding of the biology and the ecology of bioleaching. In spite of this progress, one of the aspects of biomining microbial ecology that remains un-tackled is that of virus-host interactions. The effects of viruses on the dynamics of the bioleaching microbial consortia and their impact in metal recovery is presently unknown. To begin addressing this issue we asked a basic question: ¿Are there viruses in industrial bioleaching econiches In this work, we answer that question experimentally, assessing the number and types of viral particles recovered in the leachates from different industrial settings, using epifluorescence and transmission electron microscopy. Findings emerging from this work point to an almost null presence of viral particles in the leachates from mineral processing operations, possibly due to structural stability issues of the particles in the extreme acidic and highly oxidant conditions favoured by their potential microbial hosts. In turn, DNA-loaded viral-size vesicles of presently unknown function are frequent and abundant in all samples analysed.

Abstract: Selenate removal from mine waters is required to mitigate human and environmental health impacts. In this study, the performance of an inverse fluidised bed reactor (IFBR) for the biological removal of selenate from synthetic mine water (pH 6.0-7.0) was evaluated. A laboratory-scale IFBR was set up with floating biomass carriers. Selenate reducers were enriched from environmental samples and anaerobic sludge. The synthetic medium contained ~10 mM (~1.4 g L^-1) selenate, nutrients and 10 mM ethanol as electron donor. During stable performance the bioreactor achieved 94 % removal of selenate representing a removal rate of 251 mg L^-1 d^-1 at a hydraulic retention time of 5 d. Selenite concentration remained < 1 mg L^-1 during stable performance, and the formation of a red precipitate indicated that selenate was reduced to elemental selenium. The biological selenate reduction generated alkalinity, increasing the wastewater pH from 6.0 to 8.6. The redox potential gradually approached a value ranging from -300 mV to -400 mV against standard hydrogen electrode. Overall, the results showed that the IFBR can be used for removing selenate and acidity from mine waters. Moreover, it has potential to facilitate recovery of elemental selenium. Therefore, the bioprocess provides an opportunity to reduce the costs and liabilities associated with selenium containing mine drainage and the associated environmental impacts.

Abstract: Lateritic deposits containing rare earth elements (REE) are important resources in Brazil, where monazite is the main REE-bearing mineral and is frequently associated with iron hydroxy-oxides and quartz. In order to recover valuable metals such as REE and uranium, experiments were carried out under reductive mineral dissolution using Acidithiobacillus species. In terms of phosphate, aerobic reductive dissolution at pH 0.9 using A. thiooxidans extracted about 35% of that present in the ore which is and indicator of the dissolution of monazite. Although only ~9% of the cerium and 5% of the lanthanum were extracted, ~72% of the uranium was solubilized, indicating that it was more susceptible to extraction by reductive dissolution than the other two REE.

Abstract: “Deep in situ biomining”, widely considered to be a potentially environmentally-benign and cost effective biotechnology for extracting and recovering base metals from deep-buried base metal deposits, is being developed within the EU Horizon 2020 project “BioMOre”. Data are presented from non-aerated column experiments in which a saline, calcareous copper-rich ore (kupferschiefer) was subjected to a three-stage eaching protocol: (i) with water, to remove soluble salts; (ii) with sulfuric acid, to remove calcareous minerals and other acid-soluble salts; (iii) indirect bioleaching with a microbiologically-generated ferric iron lixiviant. Sequential leaching with water and acid removed ~85% of the chloride prior to bio-processing, while ~13% of the copper present in the ore was leached using sulfuric acid, and a further 39 - 59% by the lixiviant.