Bioreactor Research Articles

Economically and technically feasible treatment for residue-driven leachate of landfills

Sri Lankan government has a policy on land filling along with the implementation of 3R (Reduce, Reuse, Recycle) where landfills are to be used only to dispose residue waste instead of unsorted waste. Sri Lanka, in response to this policy, has planned to have several landfills in the country with a view to managing the residue waste generated following the process of composting. Residue-waste comprise of long term biodegradable waste or/and non-biodegradable waste where the long term biodegradables account for large amount of tannins, cellulose, hemicelluloses. These tannins can accumulate to a level that is toxic to bacterial degradation. Tannin is characterized with high COD, BOD, TOC and turbidity levels in leachate. There has been an issue of only using biological treatment for residue-driven leachate as it may create a situation where biological treatment alone would not be possible to yield the acceptable level of treatment. Hence, it is of utmost importance to eliminate tannin prior to biological treatment. This study was carried out to find the most economical and technically feasible method to treat residue-driven leachate. Chemical treatment encompassing coagulation and flocculation chemical process is used to treat tannin in residue-driven leachate with different combinations of coagulants and flocculants at pH 7. Optimum treatment results were observed with a combination of alum and a polyelectrolyte having removal efficiencies for COD, BOD, TOC, turbidity, and tannin to be in the range of 38-40%, 25-28%, 92%, 85% and 80% respectively. It was also noted that the black color changed to colorless indicating higher levels of tannin removal. Further, the sludge arising from chemical treatment that would be easily managed within the landfill is an added advantage. Thus removal of tannin from residue driven leachate with chemical treatment prior to the biological treatment is highly recommended. As chemically treated residue-driven leachate showed BOD and COD levels higher than the proposed leachate emission levels an aerobical treatment using activated sludge can be carried out with the bio reactor. Keywords: Chemical treatment, Coagulation, Leachate, Residue-waste

In-situ hydrogen generation from 1,2,3,4-tetrahydronaphthalene for catalytic conversion of oleic acid to diesel fuel hydrocarbons: Parametric studies using Response Surface Methodology approach

This work reported a new strategy in producing synthetic diesel hydrocarbons from a mono-unsaturated fatty acid model compound, oleic acid and replacing high pressure molecular hydrogen with a hydrogen-rich donor solvent, 1,2,3,4–tetrahydronaphthalene for the first time. Under the absence of an external H2 supply, oleic acid was dispersed in 1,2,3,4-tetrahydronaphthalene and hydrotreated over commercially available 5 wt% Pd/C in a fed-batch reactor to obtain diesel range fuel products. A maximum oleic acid conversion of 92.4% and highest diesel hydrocarbon selectivity of 67.4% were achieved at 330 °C with a solvent to fatty acid mass ratio of 1 for 3 h under autogenous pressure. In-situ H2 produced from 1,2,3,4-tetrahydronaphthalene operated as an effective hydrogen donor vehicle that continuously transported active hydrogen species from gas phase to reactant acid molecules and radical fragments. It minimized polymerization of reaction intermediate and suppressed coke formation, which subsequently improved catalyst resistance toward deactivation.

Correction: Effects of collagen matrix and bioreactor cultivation on cartilage regeneration of a full-thickness critical-size knee joint cartilage defects with subchondral bone damage in a rabbit model.

[This corrects the article DOI: 10.1371/journal.pone.0196779.].

Combined CLEAs of invertase and soy protein for economically feasible conversion of sucrose in a fed-batch reactor

Invertase was immobilized using the cross-linked enzyme aggregate (CLEA) methodology using soy protein as co-feeder. The immobilized invertase retained around 30% of the initial activity after enzyme leaching assay. Maximum activity for the immobilized invertase was at 50.8°C (5.8°C higher than the soluble invertase) and at pH 5.0 (similar to the soluble invertase). The catalytic efficiency (kcat/Km) of invertase did reduce approximately tenfold after immobilization, probably due to diffusional delays. The immobilized invertase could be recycled tenfold in 4h-batches of hydrolysis of sucrose at 40°C and pH 6.0, maintaining the reaction conversion above 75%. The hydrolysis of sucrose catalyzed by immobilized invertase showed to be economically feasible in an operational window built based on economic metrics for a fed-batch process, with three intermittent feeds of sucrose to restore the substrate concentration at 100gL−1 when the conversion reaches 95%. This work represents an advance in the field, because using a carrier-free and recyclable biocatalyst the specific productivity (gram of products per gram of biocatalyst per hour) of invert sugar was as high as those previously reported for invertase immobilized on solid carriers, which may dilute its volumetric activity and increase the cost of the biocatalyst.

Neural Model to Describe Microbial Concentration in the Bioreactor for Biosurfactant Production Using Waste Substrate

Biosurfactants are produced through metabolism of microorganisms (bacteria, yeast and fungi) and many applications are attributed to them. Biomass concentration is an important variable in biosurfactant production process, because is related to substrate consumption and production rate. This variable is collected by sampling and determined by off-line analysis with significant time delay, in most of cases. The present work was carried out the development of models based on artificial intelligence to predict biomass concentration faster than usual analytical method (dry weight). The process was performed in batch-bioreactor using waste substrate. Feedforward neural networks were compared to determine the best model due to the database set acquired from the bioreactor plant. Software MATLAB 2016b was used to implement artificial neural network. The available input layers were agitation, aeration, absorbance, glucose concentration, dissolved oxygen concentration, surface tension and surface tension dissolved in 10 × and 100 ×. The network topology was determined by the combination of parameters such as number of neurons, training algorithm and activationfunctions. The results showed that the models are appropriate to predict the biomass concentration profile with good agreement of R2 (0.988), sum squared error (SSE) was 0.081 and mean squared error (MSE) was 0.0001.

Cocoa residues as viable biomass for renewable energy production through anaerobic digestion

The aim of this work was to evaluate the bioenergy potential of cocoa residue via anaerobic digestion. Batch and fed-batch lab-scale reactors were operated under low and high solids conditions. In the batch tests, 59 ± 4% of Chemical Oxygen Demand (COD) was recovered as methane. This corresponded with an average methane yield of 174 (wet) and 193 (dry) L kg−1 volatile solids fed, whereas a series of fed-batch reactors produced 70 ± 24 (wet) and 107 ± 39 (dry) L CH4 kg−1 volatile solids fed during stable conditions. A case study was developed for canton Balao (Ecuador) based on our experimental data, operational estimates and available cocoa waste in the area. Annually, 8341 MWh could be produced, meeting 88% of the current electricity demand in Balao. This case study proves the potential for cocoa waste as a source of renewable energy in rural areas.

Multi-criterion control of a bioprocess in fed-batch reactor using EKF based economic model predictive control

This research paper presents an offline and online user defined priority driven multi-objective optimal control study of a bioprocess in a fed-batch reactor. Productivity and the amount of substrates used in the process are considered as the two control objectives in that order of priority for this purpose. The priorities in the objective functions are realized using the lexicographic approach by sequentially solving multiple objectives to arrive at a Pareto solution point. This approach is not sensitive to the tuning of weighting parameters as compared to the scalarized objective, practiced conventionally. The weighting factors tuning issue is demonstrated with an offline optimal control. The lexicographic optimization approach is then implemented to overcome this thing issue. Subsequently, the online optimal control problem is solved using economic model predictive control (EMPC) owing to the economic nature of the control objectives. Often, the Pareto curve is such that marginally relaxing one objective results into a significant improvement in the other objective. This can easily be implemented with the lexicographic approach and is demonstrated using EMPC. Moreover, unlike the continuous processes, the batch processes operate for a specific batch time. Hence, the shrinking horizon approach along with the EMPC framework is employed in the fed-batch bioreactor for online control with extended Kalman filter (EKF).

POLYHYDROXYALKANOATES (PHAS) PRODUCTION FROM AEROBIC-MIXED CULTURES

This study assessed the optimal conditions for PHA production using saponified fatty acid, derived from sunflower oil (SO). A fed-batch reactor was used to produce PHA. A mixture of sewage and semi-treated oil palm effluent from a facultative pond was cultured for six months to obtain a steady-state condition. The culture was then transferred to the fed-batch system. SO mainly contains long-chain-fatty-acid (LCFA) with unsaturated fatty acid fractions of C14:1 – C18:3, therefore the PHA production was assessed under feast-famine condition. The main purpose of supplementing saponified SO was to improve the production of PHA constituents (copolymer of hydroxyl-unit) such as hydroxybutyrates (HBs), hydroxyvalerates (HVs) and hydroxyhexanoates (HHs) in mixed cultures. Fed-batch operation under aerobic-mixed cultures increased the PHA production up to 33% of the dried cell. Although sludge submitted to aerobic condition in mixed cultures could improve the PHA production, the production rates are still low. This study found that the HBs constituent in the sludge is always higher compared to HVs and HHs. Saponified SO has high specific PHA storage rates (qp feast = 0.5 C-mol/C-mol. h) which are comparable to other vegetable oils (e.g. corn oil, soy bean oil, etc.)

Review on the Characteristic and Feasibility of Leachate for Biogas Production by Anaerobic Digestion

The sound handling of municipal solid waste (MSW) is of high priority to minimise environmental degradation and pollution. MSW can be treated via various technologies including landfilling, incineration, composting, anaerobic digestion (AD) and more. Landfill without landfill gas capturing serves as an enclosed bioreactor to store and stabilise waste. Other technologies such as incineration, composting and AD allow substantial volume reduction and generate value-added products. The treatment for MSW is commonly focusing on the solid part. Organic waste contains high moisture content of 70 - 90 %. The pressing of the water content before entering treatment unit, the release of water during and after the treatment, can generate high strength wastewater, known as leachate. Leachate is rich in organic matter, organic pollutants, pathogens, heavy metals and more, which can lead to severe secondary environmental pollution if not properly treated. Leachate from different treatment units showed certain unique characteristics, such as high Na, high Ca , different species and availability of heavy metals. This review summarised some of the important characteristics of different leachates and the suitability of AD as a mean of treatment. The efficiency of AD to treat leachate was presented in terms of the removal efficiency of chemical oxygen demand (COD) and biogas production. The COD removal efficiency was between 60 - 98 %, following the treatment of different leachates under different reactors and operational parameters. Among the different stream of leachates, the leachate from landfill is most commonly studied as a co-digestion substrate for AD, as compared to leachate from the composting facility.

New insights on the mechanism of vapour phase hydrolysis of sodium borohydride in a fed-batch reactor

This study aims to produce H2 from sodium borohydride (NaBH4) and to initiate its hydrolysis at elevated temperature in the absence of a catalyst. Experimental results indicated that the hydrogen generation yield increased up to %99 at 150 °C in the NaBH4 concentration of %5 wt in the acidic medium. It can be concluded that experimental characterization of the by-products is quite important since they affected the reaction mechanism or pathway. When the experiments are carried out under aqueous condition, the primary by- product is sodium metaborate while it is boric acid under acidic condition. It is postulated that by-product boric acid decreased the mass transfer limitation due to its higher solubility that prevents the formation of shell and thus increases the contact area between NaBH4 and vapor. A series of fed-batch reactions were performed to confirm the hypothesis, and the conversions of NaBH4 reached 99% under the acidic condition.

Evaluation of Continuous Membrane Chromatography Concepts with an Enhanced Process Simulation Approach.

Modern biopharmaceutical products strive for small-scale, low-cost production. Continuous chromatography has shown to be a promising technology because it assures high-capacity utilization, purity and yield increases, and lower facility footprint. Membrane chromatography is a fully disposable low-cost alternative to bead-based chromatography with minor drawbacks in terms of capacity. Hence, continuous membrane chromatography should have a high potential. The evaluation of continuous processes goes often along with process modeling. Only few experiments with small feed demand need to be conducted to estimate the model parameters. Afterwards, a variety of different process setups and working points can be analyzed in a very short time, making the approach very efficient. Since the available modeling approaches for membrane chromatography modules did not fit the used design, a new modeling approach is shown. This combines the general rate model with an advanced fluid dynamic distribution. Model parameter determination and model validation were done with industrial cell cultures containing Immunoglobulin G (IgG). The validated model was used to evaluate the feasibility of the integrated Counter Current Chromatography (iCCC) concept and the sequential chromatography concept for membrane adsorber modules, starting with a laboratory-type module used for sample preparation. A case study representing a fed-batch reactor with a capacity from 20 to 2000 L was performed. Compared to batch runs, a 71% higher capacity, 48.5% higher productivity, and 38% lower eluent consumption could be achieved.

Design of neural network model-based controller in a fed-batch microbial electrolysis cell reactor for bio-hydrogen gas production

One of major challenge in bio-hydrogen production process by using MEC process is nonlinear and highly complex system. This is mainly due to the presence of microbial interactions and highly complex phenomena in the system. Its complexity makes MEC system difficult to operate and control under optimal conditions. Thus, precise control is required for the MEC reactor, so that the amount of current required to produce hydrogen gas can be controlled according to the composition of the substrate in the reactor. In this work, two schemes for controlling the current and voltage of MEC were evaluated. The controllers evaluated are PID and Inverse neural network (NN) controller. The comparative study has been carried out under optimal condition for the production of bio-hydrogen gas wherein the controller output is based on the correlation of optimal current and voltage to the MEC. Various simulation tests involving multiple set-point changes and disturbances rejection have been evaluated and the performances of both controllers are discussed. The neural network-based controller results in fast response time and less overshoots while the offset effects are minimal. In conclusion, the Inverse neural network (NN)-based controllers provide better control performance for the MEC system compared to the PID controller.

The application of moving bed bio-reactor (MBBR) in commercial laundry wastewater treatment

Large, laboratory scale biological treatment tests of real industrial wastewater, generated in a large industrial laundry facility, was conducted from October 2014 to January 2015. This research sought to develop laundry wastewater treatment technology which included tests of a two-stage Moving Bed Bio Reactor (MBBR); this had two reactors, was filled with carriers Kaldnes K5 (specific area – 800 m2/m3) and were realized in aerobic condition. Operating on site, in the laundry, reactors were fed actual wastewater from the laundry retention tank. The laundry wastewater contained mainly surfactants and impurities originating from washed fabrics; a solution of urea to supplement nitrogen content and a solution of acid to correct pH were added. The daily flow of raw wastewater Qd varied from 0.6–1.0 m3/d. Wastewater quality indicators showed that the reduction of pollutants was obtained: BOD5 by 95–98%, COD by 89–94%, the sum of anionic and nonionic surfactants by 85–96%. The quality of the purified wastewater after the start-up period met legal requirements regarding the standards for wastewater discharged into the environment.

Studies on Characterization of Mechanically Biologically Treated Waste from Bangalore City

The paper presents results of a comprehensive study on characterization of mechanically biologically treated waste generated in Bangalore, India. Physical, biochemical and engineering characteristics of the waste are presented. The methodology to separate the components of consolidation which includes primary, secondary and biodegradation strains is reviewed. A laboratory scale anaerobic bioreactor depicting the behaviour of the waste in a bioreactor landfill was studied for 370 days and the settlement, gas generation and leachate characteristics were monitored. Study on characterization of waste indicates an organic content of 54% and carbon, nitrogen and hydrogen in the range of 19.28, 1.64 and 11.07% respectively. Around 20–26% of settlement and 15 L of landfill gas/kg of dry waste was observed in laboratory scale bioreactor studies. Both laboratory and small scale bioreactor test results indicate that the MSW has high biodegradable content and biomethane potential. It is prone to large settlements and has shear strength parameters comparable to those published in literature. The behaviour of waste under given conditions can be understood from the above studies and the results provide valuable data necessary for designing MSW treatment scheme which includes waste to energy systems and bio reactor landfill with gas and leachate collection systems.

Production of Selenium-Enriched Yeast (Kluyveromyces marxianus) Biomass in a whey-based Culture Medium

Fil: Gurdo, Nicolas. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Conicet - La Plata. Instituto de Investigaciones Biotecnologicas. Instituto de Investigaciones Biotecnologicas Dr. Raul Alfonsin (sede Chascomus). Universidad Nacional de San Martin. Instituto de Investigaciones Biotecnologicas. Instituto de Investigaciones Biotecnologicas Dr. Raul Alfonsin (sede Chascomus); Argentina

Mathematical model of the MenD-catalyzed 1,4-addition (Stetter reaction) of α-ketoglutaric acid to acrylonitrile

The Stetter reaction, a conjugate umpolung reaction, is well known for cyanide-catalyzed transformations of mostly aromatic aldehydes. Enzymatic Stetter reactions, however, have been largely unexplored, especially with respect to preparative transformations. We have investigated the kinetics of the MenD-catalyzed 1,4-addition of α-ketoglutaric acid to acrylonitrile which has shown that acrylonitrile, while an interesting candidate, is a poor substrate for MenD due to low affinity of the enzyme for this substrate. The kinetic model of the reaction was simplified to double substrate Michaelis–Menten kinetics where the reaction rate linearly depends on acrylonitrile concentration. Experiments at different initial concentrations of acrylonitrile under batch, repetitive batch, and fed-batch reactor conditions were carried out to validate the developed mathematical model. Thiamine diphosphate dependent MenD proved to be quite a robust enzyme; nevertheless, enzyme operational stability decay occurs in the reactor. The spontaneous reactivity of acrylonitrile towards polymerization was also taken into account during mathematical modeling. Almost quantitative conversion of acrylonitrile was achieved in all batch reactor experiments, while the yield of the desired product was dependent on initial acrylonitrile concentration (i.e., the concentration of the stabilizer additive). Using the optimized reactor parameters, it was possible to synthesize the product, 6-cyano-4-oxohexanoic acid, in a concentration of 250 mM. The highest concentration of product was achieved in a repetitive batch reactor experiment. A fed-batch reactor experiment also delivered promising results, especially regarding the short reaction time needed to achieve a 200 mM concentration of product. Hence, the enzymatic Stetter reaction with a highly reactive acceptor substrate can be performed on a preparative scale, which should enable similar transformations with acrylate, methacrylate, and methyl vinyl ketone.

Glucansucrase (mutant) enzymes from Lactobacillus reuteri 180 efficiently transglucosylate Stevia component rebaudioside A, resulting in a superior taste

Steviol glycosides from the leaves of the plant Stevia rebaudiana are high-potency natural sweeteners but suffer from a lingering bitterness. The Lactobacillus reuteri 180 wild-type glucansucrase Gtf180-ΔN, and in particular its Q1140E-mutant, efficiently α-glucosylated rebaudioside A (RebA), using sucrose as donor substrate. Structural analysis of the products by MALDI-TOF mass spectrometry, methylation analysis and NMR spectroscopy showed that both enzymes exclusively glucosylate the Glc(β1→C-19 residue of RebA, with the initial formation of an (α1→6) linkage. Docking of RebA in the active site of the enzyme revealed that only the steviol C-19 β-D-glucosyl moiety is available for glucosylation. Response surface methodology was applied to optimize the Gtf180-ΔN-Q1140E-catalyzed α-glucosylation of RebA, resulting in a highly productive process with a RebA conversion of 95% and a production of 115 g/L α-glucosylated products within 3 h. Development of a fed-batch reaction allowed further suppression of α-glucan synthesis which improved the product yield to 270 g/L. Sensory analysis by a trained panel revealed that glucosylated RebA products show a significant reduction in bitterness, resulting in a superior taste profile compared to RebA. The Gtf180-ΔN-Q1140E glucansucrase mutant enzyme thus is an efficient biocatalyst for generating α-glucosylated RebA variants with improved edulcorant/organoleptic properties.

Kinetics of homogeneous and heterogeneous reactions in the reductive aminolysis of glucose with dimethylamine

The reductive aminolysis of glucose with dimethylamine (DMA) as aminating agent has been investigated experimentally as well as via kinetic model construction. A fed-batch reactor configuration was used at following conditions: temperatures ranging between 383 K–398 K, total pressures from 6.0 MPa to 7.5 MPa, an overall catalyst to glucose ratio of 9–31 gcat mol−1, an overall DMA to glucose ratio of 12–24 mol mol−1 and an overall hydrogen to glucose ratio of 5–10 mol mol−1. Such a reactor configuration, combined with a controlled feeding rate of the sugar, allowed to significantly avoid degradation reactions. The main desired products, i.e., dimethylaminoethanol (DMAE) and tetramethylethylenediamine (TMEDA), were obtained after amination followed by retro-aldol cleavage with maximum selectivity, amounting up to 15% and 60% respectively. Retro-aldol cleavage after amination proceeds at lower temperatures, evidenced by an activation energy of 60 kJ mol−1, than without amination, where activation energies amounting to 140 kJ mol−1 have been reported. A higher catalyst to glucose ratio leads to more parallel side products such as N,N-dimethylglucamine and 4‐dimethylamino-1,2,3-butanetriol. The effects of temperature and catalyst to glucose ratio were much more pronounced than that of the total pressure or the ratio of the aminating agent to glucose. The developed kinetic model is based on the most prominent homogeneous bulk phase and heterogeneously catalyzed reactions and accounts quantitatively for degradation reactions. A statistically and physically significant model which could satisfactorily reproduce the experimental observations, was thus obtained.

Removal of ozonation products of pharmaceuticals in laboratory Moving Bed Biofilm Reactors (MBBRs)

The major pathway of pharmaceuticals from urban applications to urban surface waters is via wastewater treatment plants. Ozonation is able to remove pharmaceuticals from wastewater effluents. However, during that reaction, ozonation products are formed. Some ozonation products were found to be persistent and have adverse effect on the environment. Moving bed bio reactors (MBBRs) were tested for the removal of the ozonation products of macrolide antibiotics and diclofenac at two different concentration levels 1 μg/L and 10 μg/L in laboratory reactors. It was found that the MBBRs are capable of degrading these compounds without back-transformation into the parent compounds. However, reaction rate constants and the degradation kinetics varied for different compounds and different concentrations. Depending on compound and conditions, the degradation reaction kinetics was found to follow either i) zero order ii) first order or iii) lag phase succeeded by first order. The study has proven that MBBRs have the potential to be efficient in polishing post ozonation treatment.

Membrane fouling reduction using electro-coagulation aided membrane bio-reactor

Membrane fouling reduction using electro-coagulation aided membrane bio-reactor