Continuous Stirred Tank Bioreactor Research Articles

Bioprocess Intensification of a Continuous-Flow Enzymatic Bioreactor via Productivity Dynamic Optimization under Modeling Uncertainty

In this contribution, a class of observer-based optimal feedback control is designed. The proposed feedback control is based on the Euler–Lagrange theoretical framework, and it is motivated by the productivity intensification from the chemical reactors, which is optimally increased. A Lagrangian is computed by employing the corresponding mass balance equation of a specifically selected biochemical compound. The resulting optimal controller is coupled with a novel uncertainty estimator with bounded feedback to derive an accurate estimation of the unknown terms and functions, mostly related to the reaction rate. Via Lyapunov analysis, it was shown that the proposed observer is asymptotically stable. The estimation of the unknown terms and functions is used by the proposed controller. The proposed methodology is applied to a generic model of an enzymatic biochemical continuous reactor with complex oscillatory dynamic behavior described by mass balance equations, so, in general, the proposed controller may be applied to any continuous stirred tank bioreactor; that is, the controller is independent of the specific kinetic functions. Numerical simulations show a satisfactory performance of the proposed control strategy.

Neuro-fuzzy modelling of a continuous stirred tank bioreactor with ceramic membrane technology for treating petroleum refinery effluent: a case study from Assam, India.

A continuous stirred tank bioreactor (CSTB) with cell recycling combined with ceramic membrane technology and inoculated with Rhodococcus opacus PD630 was employed to treat petroleum refinery wastewater for simultaneous chemical oxygen demand (COD) removal and lipid production from the retentate obtained during wastewater treatment. In the present study, the COD removal efficiency (CODRE) (%) and lipid concentration (g/L) were predicted using two artificial intelligence models, i.e., an artificial neural network (ANN) and a neuro-fuzzy neural network (NF-NN) with a network topology of 6-25-2 being the best for NF-NN. The results revealed the superiority of NF-NN over ANN in terms of determination coefficient (R2), root mean square error (RMSE), and mean absolute percentage error (MAPE). Three learning algorithms were tested with NF-NN; among them, the Bayesian regularization backpropagation (BR-BP) outperformed others. The sensitivity analysis revealed that, if solid retention time and biomass concentrations were maintained between 35 and 75h and 3.0g/L and 3.5g/L, respectively, high CODRE (93%) and lipid concentration (2.8g/L) could be obtained consistently.

An indigenous tubular ceramic membrane integrated bioreactor system for biodegradation of phthalates mixture from contaminated wastewater.

Endocrine-disrupting phthalates (EDPs) are widely used as plasticizers for the manufacture of different plastics and polyvinyl chloride by providing flexibility and mechanical strength. On the other hand, they are categorized under priority pollutants list due to their threat to human health and the environment. This study examined biodegradation of a mixture of dimethyl, diethyl, dibutyl, benzyl butyl, di-2-ethylhexyl, and di-n-octyl phthalates using a CSTB (continuous stirred tank bioreactor) operated under batch, fed-batch, continuous, and continuous with biomass recycle operation modes. For operating the CSTB under biomass recycle mode, microfiltration using an indigenous tubular ceramic membrane was employed. Ecotoxicity assessment of the treated water was carried out to evaluate the toxicity removal efficiency by the integrated bioreactor system. From the batch experiments, the EDPs cumulative degradation values were 90 and 75% at 1250 and 1500mg/L total initial concentration of the mixture, respectively, whereas complete degradation was achieved at 750mg/L. In the fed-batch study, 93% degradation was achieved at 1500mg/L total initial concentration of the mixture. In continuous operation mode, 94 and 85% degradation efficiency values were achieved at 43.72 and 52.08mg/L⋅h inlet loading rate of phthalate mixture. However, continuous feeding with 100% biomass recycle revealed complete degradation at 41.67mg/L⋅h inlet loading rate within the 84h operation period. High seed germination index and low mortality percentage of brine shrimps observed with phthalate degraded water from the integrated bioreactor system revealed its excellent potential in the treatment and toxicity removal of phthalates contaminated environment.

Intensification of enzymatic saccharification at high solid loading of pretreated agave bagasse at bioreactor scale

Enzymatic saccharification of pretreated lignocellulosic biomass is a key step in the biochemical biorefineries. To be economically practical for large-scale use, the process must be run at high solids loadings, notably biomass concentrations of more than 15 % (w/v). However, as the solids loading increases, biomass develops a high-viscosity slurry that is severely mass transfer constrained and more difficult to mix, which restricts the addition of even more solids. Using a commercial enzyme mixture of cellulases and hemicellulases, high solid loading hydrolysis of hydrothermally and CO2-H2O pretreated agave bagasse was carried out in a continuous stirred tank bioreactor (CSTBR) and horizontal bioreactor (HB) to generate high glucose concentrations. With complete saccharification of 100 %, operation at the CSTBR at 20 % (w/v) solid loading yielded 119.9 g/L of glucose concentration, while operating at the HB at the same level of substrate loading was able to produce 134.4 g/L of glucose concentration. CO2-H2O pretreated biomass produced 123.6 g/L of glucose at the same loading on operation with a HB. The hydrolysis was greatly enhanced by the enzyme mixture. The current glucose conversion outcomes of hydrothermally processed biomass were unquestionably greater, with an energy efficiency 2.291 gsugar/MJ. The results of the present study conclusively show the concentration of glucose working at high solid loading by analyzing the energy consumption to improve the mechanical phenomenon at the stage of pretreatment hydrolysis. For the development of biorefineries, the design and development of this process will enable the establishment of ideal operating conditions and energy efficiency.

A novel nonlinear sliding mode observer to estimate biomass for lactic acid production

Abstract This study deals with the problem of estimating the amount of biomass and lactic acid concentration in a lactic acid production process. A continuous stirred tank bioreactor was used for the culture of Lactobacillus helveticus. A nonlinear sliding mode observer is proposed and designed, which gives an estimate of both the biomass and lactic acid concentrations as a function of glucose uptake from the culture medium. Numerical results are given to illustrate the effectiveness of the proposed observer against a standard sliding-mode observer. It was found that the proposed observer worked very well for the benchmark bioreactor model. Also, the numerical results indicated that the proposed estimation methodology was robust to the uncertainties associated with un-modelled dynamics. These new sensing technologies, when coupled to software models, improve performance for smart process control, monitoring, and prediction.

Scale-up of hydrothermal processing: Liquid hot water and pilot-scale tubular steam explosion batch reactor for bioethanol production using macroalgae Sargassum spp biomass

Sargassum spp. is a biomass that can potentially use as an alternative for bioethanol production. Hydrothermal processes (liquid hot water and steam explosion pretreatment) were carried out at different operational conditions. Enzymatic hydrolysis performed a preliminary test with different ratios 1:1 and 1:2 (cellulases and hemicellulases) of enzyme loading, once selected 1:2 ratio was obtained conversion yield of 99.91% and therefore carried a scale-up in stirred bioreactor getting 95.92% saccharification yield. Pre-simultaneous saccharification and fermentation strategy was performed in a continuous stirred tank bioreactor (CSTBR), producing ethanol yield of 57.69%, and for simultaneous saccharification and fermentation strategy was performed in a bubble column reactor was 71.37% ethanol yield. The energy efficiency was analyzed in different scenarios; the best data was 30.19 (gsugar/MJ) in the bioreactor enzymatic hydrolysis process. This development allows for establishing the conditions for a third-generation biorefinery on a circular bioeconomy using Sargassum biomass.

Manganese Removal from Acid Mine Drainage by a Consortium of Mn-Oxidizing Bacteria in Continuous Stirred Tank Bioreactor: Long-Term Treatment and Reactive Mixture Characterization

Biological treatments based on Mn-oxidizing bacteria can effectively remove Mn from contaminated water. However, the mechanisms and key organisms of biological low-pH Mn(II) removal are largely unexplored. In this study, bioremediation based on an enriched consortium of acid-resistant Mn-oxidizing bacteria for Mn-rich acid mine drainage (AMD) was evaluated in a continuous stirred tank bioreactor (CSTB), and the removal mechanism of Mn(II) was further studied. The highest removal rate of 33.2 ± 1.8 mg/L/d and maximum removal efficiency of 82.4 ± 1.8% were achieved with a pH of 5.5, hydraulic retention time (HRT) of 48 h, chemical oxygen demand (COD) concentration of 2000.0 mg/L, and Mn concentration of 80.0 mg/L, respectively. The Mn oxidation rate was ∼4.1 μM/h in the continuous stirred tank bioreactor (CSTB) under stable conditions. Acinetobacter and Azospirillum were the main contributors for Mn oxidation in the bioreactor. X-ray diffraction (XRD) analysis suggested that Mn removal proceeds via the formation of biogenic precipitates consisting of MnO2, MnOOH, and MnCO3. The performance of the CSTB was further evaluated by actual Mn-rich acid mine drainage, and Mn, Cu, Zn, and Cd removal efficiencies were 86.5 ± 2.4%, 98.8 ± 2.2%, and 96.9 ± 1.0%, and 97.0 ± 1.7%, respectively. Results from this work have demonstrated that Mn-oxidizing bacteria can be effective at processing complex Mn-rich acid mine drainage.

Biodegradation and toxicity removal of phthalate mixture by Gordonia sp. in a continuous stirred tank bioreactor system

This study evaluated degradation of a mixture of six phthalates (dimethyl phthalate, diethyl phthalate, dibutyl phthalate, di-n-octyl phthalate, di-(2-ethylhexyl) phthalate and benzyl butyl phthalate) at different initial concentrations using Gordonia sp in batch shake flasks and in a continuous stirred tank bioreactor. Experiments using simple shake flasks were initially carried out as per the statistically valid 26 1/4 factorial design, which composed of 16 experimental runs with different concentrations of the phthalates. Among the different compounds, dimethyl, diethyl, and dibutyl phthalates, showed more than 99% degradation efficiency even at their high initial concentration. Based on the results of the shake flask study, bioreactor experiments were carried out with 750, 1250 and 1500 mg/L total concentration of the phthalates in mixture. The biodegradation efficiency values of the phthalates using the bioreactor were very high compared with their biodegradation in shake flasks owing to efficient mass transfer, agitation and pH control. Compared to degradation of the compounds at 1500 mg/L total phthalate concentration, the values obtained at 750 mg/L total phthalate concentration were superior (nearly 100% degradation efficiency). The degradation of the high molecular weight phthalates (di-n-octyl phthalate, di-(2-ethylhexyl) phthalate and benzyl butyl phthalate) were better with CSTB as compared to their degradation efficiency values obtained in the batch shake flask study. Very low phytotoxicity of the degraded phthalates further confirmed the potential of Gordonia sp. to treat phthalate contaminated systems.

Problems in volumetric flow rate and liquid level control of a continuous stirred tank bioreactor with structured and unstructured kinetics

All equipment and devices utilized in various chemical and biochemical technologies are subject to external disturbances. In continuous flow systems, usually operating under steady-state conditions, these disturbances result in departure from the steady state. The paper reports on the process consequences of perturbations of the volumetric flow rate in a continuous stirred tank microbiological reactor, and on the automatic control of the liquid level by means of continuous P and PI controllers. The dynamics of the uncontrolled and controlled bioreactor were compared based on two kinetic models: an unstructured Haldane model and an one-parameter structured model.The paper investigates the effects of sudden step and oscillatory disturbances. It was shown that, for oscillatory variations in the feed rate, the biomass washout phenomenon depends on the period of oscillation, and occurs for oscillations with a sufficiently long period. This unfavorable phenomenon can be eliminated by applying liquid level control. Additionally, it was demonstrated that the use of a structured model gives a more reliable assessment of the dynamics of uncontrolled and controlled bioreactors subjected to step forcing. If the bioreactor is subjected to sinusoidal forcing, then the type of kinetic model used, i.e. structured or unstructured, made no difference.

A comprehensive review on application of bioreactor for industrial wastewater treatment.

In the recent past, wastewater treatment processes performed a pivotal role in accordance with maintaining the sustainable environment and health of mankind at a proper hygiene level. It has been proved indispensable by government regulations throughout the world on account of the importance of preserving freshwater bodies. Human activities, predominantly from industrial sectors, generate an immeasurable amount of industrial wastewater loaded with toxic chemicals, which not only cause dreadful environmental problems, but also leave harmful impacts on public health. Hence, industrial wastewater effluent must be treated before being released into the environment to restrain the problems related to industrial wastewater discharged to the environment. Nowadays, biological wastewater treatment methods have been considered an excellent approach for industrial wastewater treatment process because of their cost-effectiveness in the treatment, high efficiency and their potential to counteract the drawbacks of conventional wastewater treatment methods. Recently, the treatment of industrial effluent through bioreactor has been proved as one of the best methods from the presently available methods. Reactors are the principal part of any biotechnology-based method for microbial or enzymatic biodegradation, biotransformation and bioremediation. This review aims to explore and compile the assessment of the most appropriate reactors such as packed bed reactor, membrane bioreactor, rotating biological contactor, up-flow anaerobic sludge blanket reactor, photobioreactor, biological fluidized bed reactor and continuous stirred tank bioreactor that are extensively used for distinct industrial wastewater treatment.

Optimum Design of N Continuous Stirred-Tank Bioreactors in Series for Fermentation Processes Based on Simultaneous Substrate and Product Inhibition

Optimization of the continuous fermentation process is important for increasing efficiency and decreasing cost, especially for complicated biochemical processes described by substrate and product inhibition. The optimum design (minimum volume) of CSTRs in series assuming substrate and product inhibition was determined in this study. The effect of operating parameters on the optimum design was investigated. The optimum substrate concentration in the feed to the first reactor was determined for N reactors in series. The nonlinear, constrained optimization problem was solved using the MATLAB function “fmincon”. It was found that the optimum design is more beneficial at high substrate conversion and at a medium level of feed substrate concentration. The best number of reactors is two to three for optimum arrangements and two for equal-size arrangements. The presence of biomass in the feed to the first reactor reduces the reactor volume, while the presence of product in the feed slightly increases the required total volume. The percentage reduction in the total volume using the optimum design compared to equal-volume design (R%) was determined as a function of substrate conversion and substrate concentration in the feed to the first reactor. The obtained R% values agree with experimental data available in the literature for ethanol fermentation.

Comparative Study for the Production of Mycophenolic Acid using Penicillium brevicompactum in Batch, Fed-batch and Continuous Fermentation Process

Mycophenolic acid (MPA) is, due to its immunosuppressive and biological activities, a potential compound. It is the secondary metabolite produced in submerged cultivation by the microfungus Penicillium brevicompactum. Batch, fed-batch, and continuous mode of cultivation for mycophenolic acid production were performed and compared in the current work. To increase productivity, mycophenolic acid production was studied in batch, fed-batch, and continuous bioreactors. These experiments were conducted with a 2.5 L working volume in a 3.7 L continuous stirred tank bioreactor. In all cases, operating conditions such as temperature, pH, agitation, and aeration, 28 °C, 5.5, 200 rpm, and 2 vvm, respectively, were the same. In fed-batch fermentation, the MPA concentration obtained was 1.91 g/L higher than the value obtained in batch culture, 1.55 g/L, while in continuous fermentation, 1.67 g/L was obtained. The mycophenolic acid productivity obtained in the continuous fermentation process was 0.025 g/L/h, which was maximum MPA productivity, compared to 0.007 g/L/h in the fed-batch fermentation process and 0.006 g/L/h in the batch fermentation process. The impact of substrate inhibition on the product formation can effectively bring down by continuous fermentation processes. The MPA productivity was increased in continuous fermentation relative to batch and fed-batch processing. The finding indicates that continuous culture of Penicillium brevicompactum is a promising strategy for the synthesis of mycophenolic acid.

Dynamical simulation of a continuous stirred tank bioreactor with the use of cellular automata for the biofilm description

The paper concerns mathematical modeling and simulation of a continuous-flow stirred tank bioreactor (CSTBR) in which heterogeneous biofilm forms on its walls. The mathematical model couples a 2D cellular-automata biofilm model with differential equations describing the liquid phase in the bioreactor. Double-substrate aerobic phenol biodegradation by Pseudomonas putida bacteria was chosen as a process example. The influence of key process parameters on the dynamical characteristics of the bioreactor and the biofilm structure evolution during the process was investigated. Such an analysis has not been previously performed. It was shown that cell death strongly affects both biofilm heterogeneity and the technological properties of the bioreactor. Neglecting this phenomenon leads to improper design of the bioreactor. The influence of substrate load on the heterogeneity of the biofilm was evaluated in the process limited by two substrates. So far only a single substrate limitation has been evaluated in this regard. Even for large carbonaceous substrate concentrations, the biofilm growth and its structure are influenced by oxygen depletion. It was shown that an increased detachment rate increases bioreactor productivity.

Biodegradation Kinetic Studies of Phenol and p-Cresol in a Batch and Continuous Stirred-Tank Bioreactor with Pseudomonas putida ATCC 17484 Cells

The biodegradation of phenol, p-cresol, and phenol plus p-cresol mixtures was evaluated using Pseudomonas putida ATCC 17484 in aerobic batch reactors. Shake-flask experiments were performed separately using growth medium with initial nominal concentrations of phenol (50–600 mg L−1) and p-cresol (50–600 mg L−1) as well as phenol (50–600 mg L−1) plus p-cresol (50–600 mg L−1). The complete degradation of phenol and p-cresol was achieved within 48 h and 48–56 h, respectively, for all initial concentrations of phenol and p-cresol. The maximum cell growth rate using phenol (μmax,P = 0.45 h−1) was much faster than that using p-cresol (μmax,C = 0.185−1 h). The larger Ki value for phenol (310.5 mg L−1) revealed that the P. putida cells had a higher resistance to phenol inhibition compared with p-cresol (243.56 mg L−1). A mixture of phenol and p-cresol in batch experiments resulted in the complete removal of phenol within 52–56 h for initial phenol concentrations of 50–500 mg L−1. The time needed to remove p-cresol completely was 48–56 h for initial p-cresol concentrations of 50–500 mg L−1. In the continuous-flow immobilized cells reactor, the degradation efficiency for phenol and p-cresol was 97.6 and 89.1%, respectively, at a stable condition.

Effective Bioremediation of Zinc(II) with Fusarium sp. in Batch and Continuous Studies

Designing desirable approach for batch and continuous methods of activity for profoundly effective removal of zinc(II) is of practical importance, given the steady, cost-effective, environmentally friendly attribute. This article offers an answer for foster a continuous stirred tank bioreactor (CSTR) containing single- and two-phase reactors for the viable continuous removal of zinc(II) from aqueous solution by making use of Fusarium sp. collected from soil under growing conditions. The different development stages Fusarium sp. were tried, including initial metal concentration, pH and growth rate in batch bioreactors. The maximum removal of zinc(II) in the batch studies indicated 63.9 mg/g, at controlled pH: 5.0; and at initial 500 mg/L zinc(II) concentration, which is almost of comparable quantity to the most extreme removal of zinc(II) (52.8 mg/g) obtained in the continuous mode of operation. A continuous flow system operated in staged manner was found to be the ideal strategy for obtaining almost complete removal at lower concentration focus up to 100 mg/L in a single stage bioreactor and a multistage reactor at higher zinc(II) concentrations.

Anoxic biogas biodesulfurization promoting elemental sulfur production in a Continuous Stirred Tank Bioreactor

Biological desulfurization of biogas has been extensively studied using biotrickling filters (BTFs). However, the accumulation of elemental sulfur (S°) on the packing material limits the use of this technology. To overcome this issue, the use of a continuous stirred tank bioreactor (CSTBR) under anoxic conditions for biogas desulfurization and S° production is proposed in the present study. The effect of the main parameters (stirring speed, N/S molar ratio, hydraulic residence time (HRT) and gas residence time (GRT)) on the bioreactor performance was studied. Under an inlet load (IL) of 100 g S-H2S m–3 h–1 and a GRT of 119 s, the CSTBR optimal operating conditions were 60 rpm, N/S molar ratio of 1.1 and a HRT of 42 h, in which a removal efficiency (RE) and S° production of 98.6 ± 0.4 % and 88 % were obtained, respectively. Under a GRT of 41 s and an IL of 232 g S-H2S m–3 h–1 the maximum elimination capacity (EC) of 166.0 ± 7.2 g S-H2S m–3 h–1 (RE = 71.7 ± 3.1 %) was obtained. A proportional-integral feedback control strategy was successfully applied to the bioreactor operated under a stepped variable IL.

Treatment of waste gas contaminated with dichloromethane using photocatalytic oxidation, biodegradation and their combinations

The treatment of waste gas (WG) containing dichloromethane (DCM) using advanced oxidation processes (AOPs) [UV and UV-TiO2], biological treatment (BT), and their combination (AOPs-BT) was tested. AOP tests were performed in an annular photo-reactor (APHR), while BT was conducted in a continuous stirred tank bioreactor (CSTBR). The effects of gas flow rate (Qgas), inlet DCM concentration ([DCM]i), residence time (τ), photocatalyst loading (PH-CL) and % relative humidity (% RH) on the AOPs performance and the removal of DCM (%DCMr) were studied and optimized. The UV process exhibited %DCMr ≤ 12.5 % for tests conducted at a [DCM]i ≤ 0.45 g/m3, Qgas of 0.12 m3/h and τ of 27.6 s, respectively, and < 4 % when the [DCM]i ≥ 4.2 g/m3. The UV-TiO2 achieved a %DCMr ≥ 71 ± 1.5 % at Qgas of 0.06 m3/h, [DCM]i of 0.45 g/m3, τ of 55.2 s, PH-CL of 10 g/m2, and %RH of 50, respectively. The BT process removed ∼97.6 % of DCM with an elimination capacity (EC) of 234.0 g/m3·h. Besides, the high %DCMr of ∼98.5 % in the UV-BT and 99.7 % in the UV-TiO2-BT processes confirms AOPs-BT as a promising technology for the treatment of recalcitrant compounds present in WG.

Parametric Sensitivity of CSTBRs for Lactobacillus casei: Normalized Sensitivity Analysis

In this paper, a sensitivity analysis of a continuous stirred tank bioreactor (CSTBR) was conducted to determine a parametrically sensitive regime. The growth of a lactic acid bacterium, namely, Lactobacillus casei, in a pH-controlled CSTBR was considered as a process model. Normalized objective sensitivities of the minimum pH were determined with respect to input parameters. A generalized criterion for sensitivity was defined for determining the parametric range of three input variables, i.e., dilution rate base stream (θ), base concentration (R), and initial pH (pH0) for maintaining optimal pH range in the reactor. The system exhibits sensitive behavior for θ, R, and pH0, from 0.095 to 0.295, 0 to 0.865, and 4.42 to 4.77, respectively. The critical values of θ, R, and pH0 are 0.0195, 0.48, and 4.6, respectively. The mathematical model can also be used to determine a parametrically sensitive regime for other important parameters, namely, temperature, the concentration of metabolites, and other byproducts. The mathematical tool can also be used in bioreactor design and the improvement of control strategies.

Pilot-scale petroleum refinery wastewaters treatment systems: Performance and microbial communities’ analysis

This study evaluated firstly the performance of the Continuous Stirred Tank bioReactor system (CSTR) for the treatment of highly toxic petroleum refinery wastewaters at the pilot-scale. The reduction of the COD, BOD5, phenols, and the total petroleum hydrocarbon (TPH) reached 82.10%, 85.87%, 91.63%, and 81.11%, respectively at high hydraulic residence time (HRT = 10 days). Decreasing HRT to 5 and 2.5 days led to a decrease in the efficiency of the process and a decrease in biomass concentration was also observed (<1000 mg/l). We investigated to test Membrane Bioreactor (MBR) configuration inoculated with the same microbial consortium of CSTR. Therefore, the removal efficiency reached 89.14% of COD and biomass concentration increased to 2800 mg/l at HRT = 1 day. Microbial biomass showed high acclimatization to the toxic wastewater. Communities’ abundance and composition in CSTR and MBR were then performed using culture-independents approaches (qPCR, Illumina Miseq sequencing, and DGGE) based on the 16S rRNA gene sequencing. Results showed that major genera affiliated with Betaproteobacteria and Gammaproteobacteria were commonly shared in both bioreactors. The MBR presented a higher bacterial abundance and diversity than the CSTR. Furthermore, dominant genera belonging to Alphaproteobacteria and Bacteroidetes were exclusively detected in CSTR and MBR, respectively. Six potential hydrocabonclastic bacteria were isolated from the CSTR. This study demonstrates the occurrence of specific acclimated bacterial communities in MBR different from those identified in CSTR, improving the petroleum hydrocarbon wastewater treatment. The results would be useful in developing an MBR system for treating toxic stripped wastewater at a larger scale.

Performance of a continuous stirred tank bioreactor employing an immobilized actinobacteria mixed culture for the removal of organophosphorus pesticides

In this study, we evaluated polyurethane foam (PF), volcanic rock (VR), and a modified plastic cap (MPC) as supports for the immobilization of organophosphorus (OP) pesticide-degrading actinobacterial strains. The colonization and activity of four streptomycetes were favoured by PF, which was selected as the carrier to use in a continuous stirred tank bioreactor (CSTR) that can be operated at increasing inflows of a pesticide mixture that contains the insecticides chlorpyrifos (CP) and diazinon (DZ). Our results demonstrate that the CSTR can be operated at flow rates of 10 and 40mLh-1 with greater than 85% removal of the pesticides in the short term. A significant decrease in the efficiency of CP removal was observed at the highest inflows into the reactor. The CP and DZ loading rates in the bioreactor ranged from 0.44 to 1.68mgL-1h-1 and from 0.50 to 2.17mgL-1h-1, respectively. Although the treated wastewater exhibited moderate toxicity for Raphanus sativus, a bioreactor inoculated with a mixed culture formed by Streptomyces spp. strains AC5, AC9, GA11 and ISP13 may provide an effective biotechnological strategy for the reduction of OP pesticide residues produced during agronomic and manufacturing practices and therefore prevent environmental pesticidal pollution.