Microorganisms In Bioreactor Research Articles

Regulation Mechanism and Optimization Strategy of Microbial Metabolism in Bioreactor

In this study, the metabolic regulation mechanism of microorganisms in bioreactor was discussed, and a series of optimization strategies were proposed based on this. The key effects of metabolic regulation on the performance of bioreactors were revealed through the overview of microbial metabolic pathways and the analysis of regulatory mechanisms. In view of this, the optimization strategy based on metabolic regulation was proposed from the aspects of metabolic engineering transformation, genetic engineering technology application, metabolic pathway reconstruction and optimization. At the same time, the operating conditions of the reactor, such as temperature, pH value, dissolved oxygen, substrate concentration and mixing effect were optimized in detail. In terms of reactor design and scale-up strategy, the scale effect, reactor configuration and flow field optimization, and heat and mass transfer enhancement technology were mainly considered. This study provides important theoretical and practical guidance for the improvement of bioreactor performance and the progress of biotechnology industry.

A bioaugmentation strategy to recover methane production under sulfate-stressed conditions: Highlights on targeted sulfate-reducing bacteria and DIET-related species

Bioaugmentation has been recognized as a key strategy to improve the anaerobic digestion efficiency in organic waste treatment. Methanosarcina barkeri possesses direct interspecies electron transfer capability, a characteristic that allows it to outcompete other unwanted species such as sulfate-reducing bacteria. This study investigated the effects of bioaugmentation with Methanosarcina barkeri DSM800 on two continuous-stirred tank reactors fed with a sulfate-rich feedstock. One of the two reactors was supplemented with magnetite to facilitate direct interspecies electron transfer. Time series quantitative polymerase chain reactions were performed to evaluate the absolute abundance of crucial species, including the augmented Methanosarcina. Results showed increased and stabilized methane production of 22% and 21% in the reactor amended with magnetite and in the control reactor, respectively. Moreover, volatile fatty acids were almost completely consumed in the magnetite-supplemented reactor. The quantitative polymerase chain reaction was used to analyze the abundance of targeted species in response to bioaugmentation. Specifically, Methanosarcina barkeri was not retained in either reactor after one hydraulic retention time. Direct interspecies electron transfer-associated microorganisms showed opposite trends in the two reactors, highlighting the different interactions with Methanosarcina barkeri in the presence and absence of magnetite. Sulfate-reducing bacteria following the dissimilatory sulfate reduction pathway exhibited an opposite behavior in the reactor amended with magnetite, in contrast to those employing the assimilatory sulfate reduction pathway. Overall, the study demonstrated that bioaugmentation with exogenous archaea can considerably alter the microbial community, but the introduced species is not able to establish itself in a stable microbiome. In addition, the strategy could be further tested to control H2S production in real-world waste treatment scenarios. Quantitative polymerase chain reaction proved to be a useful tool for monitoring changes in the absolute abundance of microorganisms in bioreactors, implementing effective monitoring and control strategies to improve overall system performance.

Beneficial Microorganisms in the Anaerobic Digestion of Cattle and Swine Excreta

The accumulation of solid organic waste is reaching critical levels in almost all regions of the world. It must be managed sustainably to avoid the depletion of natural resources, minimize risks to human health, reduce environmental burdens, and maintain an overall balance in the ecosystem. This research focuses on the anaerobic digestion of bovine and swine excreta with and without applying beneficial microorganisms as a viable option for recycling agricultural solid wastes. Three greenhouse gases (GHGs)—methane, carbon dioxide, and ammonia—produced by cattle and swine excreta that were treated with and without beneficial microorganisms in bioreactors were quantified. A monitoring and gas concentration measurement system was implemented inside the bioreactors. The behavior of the GHGs and the efficiency of the beneficial microorganisms in treating the farm animal waste were analyzed according to the phases of anaerobic digestion. Average reductions in the concentration in units of ppm of CH4 during the composting process of 46.95% and 34.48% were observed for the cattle and swine excreta treatments, respectively. It was concluded that the studied GHGs had different behaviors in the anaerobic digestion of the treatments in cattle and swine excreta with and without beneficial microorganisms due to the different types of feeding. However, it must be emphasized that beneficial microorganisms are an essential tool for reducing GHGs in anaerobic digestion.

Synergistic removal of nitrate by a cellulose-degrading and denitrifying strain through iron loaded corn cobs filled biofilm reactor at low C/N ratio: Capability, enhancement and microbiome analysis

Optimization of nitrate removal rate under low carbon-to-nitrogen ratio has always been one of the research hotspots. Biofilm reactor based on functional carrier and using interspecific synergic effect of strains provides an insight. In this study, iron-loaded corn cob was used as a functional carrier that can contribute to the cellulose degradation, iron cycling, and collaborative denitrification process of microorganisms. During biofilm reactor operation, the maximum nitrate removal efficiency was 99.30% and could reach 81.73% at no carbon source. Dissolved organic carbon and carrier characterization showed that strain ZY7 promoted the release of carbon source. The crystallinity of cellulose I and II in carrier of experimental group increased by 31.26% and decreased by 21.83%, respectively, in comparison to the control group. Microbial community showed the synergistic effect among different strains. The vitality and metabolic activity of the target microorganisms in bioreactor were increased through interspecific bacterial cooperation.

Modeling of enzymatic waste water treatment

Processing and recycling of waste water is an important environmental problem. One possible and promising way to use the generated sludge is production biofertilizers for agriculture. However, in view of the risks of chemical and bacteriological contamination, it is necessary to develop technologies that ensure a high level of conditioning and stabilization of sludge. Maximum enzyme activity is observed in a microbubble medium under the conditions of a mesophilic process. To accelerate the biochemical transformation of pollutants, an enzyme-cavitation method has been developed, based on the stimulation of growth processes of microorganisms in bioreactors by low and high intensity cavitation created by turbojets. It has been established that the quality and duration of sludge treatment depends on the pressure of the substrate at the entrance to the oxidizing jets. It has been proven that at a pressure p = 0.30-0.35 MPa, the processing time of the sludge before stabilization of the chemical oxygen consumption at 16% is 8 hours. Microscopic studies found that the processed substrate is an accumulation of microorganisms with a total surface of up to 100 m2 per 1 gram of dry matter that provides high sorption properties with respect to moisture.

Developing a method for measurement of dehydrogenase activity in biological wastewater treatment processes applied for toxic compounds degradation

Biological wastewater treatment processes are among the environmentally friendly techniques for degradation of organic compounds. They are also preferred to the physical and chemical processes which are due to the ability of biological processes to treat wide range of organic compounds with lower operational costs. However, biological processes are usually affected by variation in the inlet wastewater quality and quantity. In order to investigate the performance of the wastewater treatment plant, various parameters in case of effluent quality such as COD, BOD, TSS, TDS etc. are required to be measured. Microorganisms in bioreactors use various enzymes to degrade the organic contaminants. Higher toxic organic load on the biological process may lead to the deterioration of the process performance which is due to the reduction in microbial activity of the biomass. Dehydrogenase enzyme produced in biological processes could be used as an indicator for the biological wastewater treatment. Present study introduces a simple and modified method for evaluation of biological wastewater treatment process measuring dehydrogenase activity. In the present study, the effective parameters such as incubation time and types of solvent were investigated and the best procedure is developed for measuring the dehydrogenase activity in biological wastewater treatment process.

Production of polyhydroxyalkanoates and enrichment of associated microbes in bioreactors fed with rice winery wastewater at various organic loading rates

This study aimed to explore the production of polyhydroxyalkanoates (PHA) and selection of PHA-accumulating microorganisms in bioreactors fed with rice winery wastewater at various organic loading rates (OLRs). The substrate utilization, sludge properties, PHA synthesis and microbial community structure of three sequencing batch reactors were monitored. The results show the highest PHA yield (0.23 g/g) was achieved in one of the three reactors with an OLR of 2.4 g COD/L/d, in which Zoogloea was the most dominant PHA-accumulating microorganism. To quantify the PHA production and track the population changing profiles of the PHA-accumulating microorganisms in the long-term reactor operation, the Activated Sludge Model No. 3 was modified with two different heterotrophic microorganisms responding differently with the same substrate. The modeling results indicate that a moderate OLR (>2.4 gCOD/L/d) was beneficial for PHA production. The results are useful for understanding the PHA production from industrial wastewaters and selection of PHA-accumulating microorganisms.

Biotechnological Approaches to the Bioremediation of an Environment Polluted with Trinitrotoluene

The review covers the strategies for the biodegradation of a dangerous pollutant of the environment, an explosive 2,4,6-trinitrotoluene. The characteristics of the metabolism of this compound in microorganisms under aerobic and anaerobic conditions and the main enzymes involved in the transformation are described. The main class of enzymes involved in the destruction of trinitrotoluene are nitroreductases; oxidases, hydrogenases, and peroxidases may also be involved in degradation. Several approaches to the biodegradation of trinitrotoluene in the environment have been singled out and discussed: bioaugmentation of the biomass of TNT-destructor strains and consortia of microorganisms that degrade this compound; stimulation of the autochthonous microflora of polluted natural environments via the introduction of additional substrates for microorganism growth and electron donors for the reduction of trinitrotoluene; pollutant biodegradation by immobilized cells of microorganisms in bioreactors and biofilters; phytoremediation and the application of preventive measures consisting of the introduction of spores and lyophilisates of bacteria with biodegradation activity in a mixture containing nitroaromatic compounds.

Effect of temperature-time on sterilization process for a jacketed bioreactor system: Application of a Ratkowsky Nonlinear Model

Steam sterilization is a technique widely implemented in different biotechnological processes, among them the growth of microorganisms in bioreactors, which require initial aseptic conditions. In the present paper, it was studied the relationship between the lethality and the death rate of Bacillus cereus grown in 7 liter jacked stirred tank bioreactors was examined, where sugar cane molasses was utilized as the main culture medium. The sterilization process was tested with an industrial autoclave within data loggers in bioreactors, which measure the temperature in the cold point to quantify the accumulated lethality. Through data analysis a contour plot allows a graphical prediction of the microbiological sterilization results in terms of colony forming units (CFU). The case study shows that there is range between 16 and 20 minutes, approaching 123 °C, with a null presence of contaminant microorganisms. The surface chart demonstrates the existing non-linear relationship between the variables temperature and time involved. A positive correlation was observed using Ratkowsky mathematical model with a 0,971 correlation coefficient and the estimated value of α = 11,04 and β = -1,49 for the non-lineal model of parameterization. With these results, it is possible to predict the CFU based on data. This could provide an interesting base for future sterilization practices and a methodology as a starting point for sterilization trials in industry and save time and costs.

INTENSIFICATION OF BIOLOGICAL PROCESSES DURING THE REMOVAL OF AMMONIUM IONS FROM WATER

Currently one of the main problems in the purification of natural and sewage water is the removal from them biogenic elements – nitrogen and phosphorus that cause eutrophication of water bodies. In relation to nitrogen, there are several ways of it removal from the water. So, ammonium can be converted to ammonia and then to blown out from alkaline water, he also can be eliminated from water by the method of electrolytic oxidation, by ozonization or chlorination followed by filtration through activated carbon. Nitrates and nitrites may be removed by chemically reducing until molecular nitrogen, by using distillation or electrolysis. All three of these nitrogen compounds can be removed by ion exchange or ultrafiltration. However, all these methods require expensive reagents and equipment, they are difficult to operate and low-effective. To date, a biological method is considered as the cheapest, environmentally perfect, and therefore the most widely used method of purification from nitrogen. But according to traditional technological schemes of their elimination it requires the participation of two microbiological processes – nitrification (oxidation of ammonium ions to nitrate ions) and denitrification (recovery of nitrate ions to gaseous nitrogen). These two processes are characterized by the presence of conflicting requirements to the aquatic environment by the quantity of oxygen, organic compounds and many other parameters. In this regard, the most common scheme which results to removal from water the nitrogen compounds is a combination of classic nitrification and denitrification processes when they pass separately. The disadvantages of separate systems consist in the large costs of building separate (aerobic and anaerobic) bioreactors, the need to build secondary settling tanks after each stage of purification, which requires the construction of additional pumping stations, which lead to higher energy costs to maintain of necessary concentration of oxygen during the nitrification, etc. So, now the most promising considered the use of combination system of nitrogen removal. In such schemes, nitrification and denitrification processes are occurring in the same building (the bioreactor) simultaneously.Unresolved and controversial part in this scientific problem is optimization process of extracting nitrogen from the water flow while aerobic-anaerobic processes of nitrification and denitrification pass in the same reactor (OND phenomenon), which so far has not found an adequate explanation. Compared to classical schemes, cleaning processes using this phenomenon require less concentration of dissolved oxygen, no need to add organic matter, reduced costs for hardware, etc. However, being attractive from an economic perspective, these processes very “capricious” in their practical application.Based on the above, the purpose of our work was to find basic principles of optimization and intensification of biological processes that lead to the removal of nitrogen from the water while passing simultaneously nitrification and denitrification in a bioreactor.At the first stage of this work studied the advisability of isolate individual physiological groups of microorganisms and their associations with different habitats and environmental zones. Established that hypolimnion’s zone is the environment within which emerging microbial community, the most suitable for the efficient removal from water ammonium ions by simultaneous nitro-denitrification.A comparison of different loading materials depending on their impact on the effectiveness removal of ammonium ions from water by the microcenosis of bioreactor had also conducted. It is shown that the best filling for the aerobic-anaerobic bioreactor are the polystyrene blocks with the addition of clay minerals.The processes of improving the efficiency of extracting ammonium from the water are accompanied by changes in the dynamics of microbial populations. Thus, as a result of 3-month adapt of mycrocenosis to increased levels of ammonium ions, decrease in the number of species of microorganisms in bioreactor on half while maintaining of the percentage of anaerobic microorganisms as well as increasing the total microbial number have been observed.

Nonlinear predictive control for maximization of CO2 bio-fixation by microalgae in a photobioreactor

In the framework of environment preservation, microalgae biotechnology appears as a promising alternative for CO₂ mitigation. Advanced control strategies can be further developed to maximize biomass productivity, by maintaining these microorganisms in bioreactors at optimal operating conditions. This article proposes the implementation of Nonlinear Predictive Control combined with an on-line estimation of the biomass concentration, using dissolved carbon dioxide concentration measurements. First, optimal culture conditions are determined so that biomass productivity is maximized. To cope with the lack of on-line biomass concentration measurements, an interval observer for biomass concentration estimation is built and described. This estimator provides a stable accurate interval for the state trajectory and is further included in a nonlinear model predictive control framework that regulates the biomass concentration at its optimal value. The proposed methodology is applied to cultures of the microalgae Chlorella vulgaris in a laboratory-scale continuous photobioreactor. Performance and robustness of the proposed control strategy are assessed through experimental results.

Bioreactor monitoring with spectroscopy and chemometrics: a review

Biotechnological processes are crucial to the development of any economy striving to ensure a relevant position in future markets. The cultivation of microorganisms in bioreactors is one of the most important unit operations of biotechnological processes, and real-time monitoring of bioreactors is essential for effective bioprocess control. In this review, published material on the potential application of different spectroscopic techniques for bioreactor monitoring is critically discussed, with particular emphasis on optical fiber technology, reported for in situ bioprocess monitoring. Application examples are presented by spectroscopy type, specifically focusing on ultraviolet-visible, near-infrared, mid-infrared, Raman, and fluorescence spectroscopy. The spectra acquisition devices available and the major advantages and disadvantages of each spectroscopy are discussed. The type of information contained in the spectra and the available chemometric methods for extracting that information are also addressed, including wavelength selection, spectra pre-processing, principal component analysis, and partial least-squares. Sample handling techniques (flow and sequential injection analysis) that include transport to spectroscopic sensors for ex-situ on-line monitoring are not covered in this review.

Formation of Distinct Soluble Microbial Products by Activated Sludge: Kinetic Analysis and Quantitative Determination

Soluble microbial products (SMP) released by microorganisms in bioreactors are classified into two distinct groups according to their different chemical and degradation kinetics: utilization-associated products (UAP) and biomass-associated products (BAP). SMP are responsible for effluent chemical oxygen demand or for membrane fouling of membrane bioreactor. Here an effective and convenient approach, other than the complicated chemical methods or complex models, is developed to quantify the formation of UAP and BAP together with their kinetics in activated sludge process. In this approach, an integrated substrate utilization equation is developed and used to determine UAP and their production kinetics. On the basis of total SMP measurements, BAP formation is determined with an integrated BAP formation equation. The fraction of substrate electrons diverted to UAP, and the content of BAP derived from biomass can then be calculated. Dynamic quantification data are obtained for UAP and BAP separately and conveniently. The obtained kinetic parameters are found to be reasonable as they are generally bounded and comparable to the literature values. The validity of this approach is confirmed by independent SMP production tests in six different activated sludge systems, which demonstrates its applicability in a wide range of engineered system regarding SMP production. This work provides a widely applied approach to determine the formation of UAP and BAP conveniently, which may offer engineers with basis to optimize bioreactor operation to avoid a high effluent soluble organics from SMP or SMP-based membrane fouling in membrane bioreactors.

Estimation of kinetic rates in a baker's yeast fed-batch bioprocess by using non-linear observers

The growth rates of the micro-organisms in bioreactors are described by complex kinetic expressions, and the modelling and estimation of such kinetics are essential for the design of control strategies. This study deals with the online estimation of kinetic rates of a baker's yeast process, taking place inside a fed-batch bioreactor. This bioprocess is widely used in bioindustry; its model is highly non-linear and, furthermore, the available online measurements are missing and the reaction kinetics is not perfectly known. The unknown kinetics is estimated by using non-linear observers, based on high-gain approach. Two high-gain observers are designed and implemented: one for the specific growth rates and the other for the reaction rates of the baker's yeast bioprocess. The multiple estimation schemes do not require any model for the kinetic rates. The tuning of the proposed observers is reduced to the calibration of a single parameter. An observer-based estimator is also implemented in order to use it for comparisons. Numerical simulations are included to test the behaviour and the performance of the proposed observers.

Specific growth rate estimation in (fed-)batch bioreactors using second-order sliding observers

Abstract This paper addresses the estimation of specific growth rate of microorganisms in bioreactors using sliding observers. In particular, a second-order sliding observer based on biomass concentration measurement is proposed. Differing from other proposals that only guarantee bounded errors, the proposed observer provides a smooth estimate that converges in finite time to the time-varying parameter. Stability is proved using a Lyapunov approach. The observer exhibits also robustness to process uncertainties since no model of the reaction is used for its design. In addition, the off-surface coordinate of the sliding observer is useful to determine the convergence time as well as to identify sensor faults and unexpected behaviors. Because of the structure of the output error injection, chattering phenomena of conventional sliding mode algorithms are substantially reduced. The features of the proposed observer are assessed by numerical and experimental data.

Specific Growth Rate Estimation in Bioreactors Using Second-Order Sliding Observers

This paper addresses the estimation of specific growth rate of microorganisms in bioreactors. In particular, a second-order sliding observer based on biomass concentration measurement is proposed. Differing from other proposals that only guarantee bounded errors, the observer provides a smooth estimate that converges in finite time to the time-varying parameter. Further, the observer exhibits very robust properties since no model of the kinetics is used for its design. In addition, the off-surface coordinate of the sliding observer is useful to determine the convergence time as well as to identify sensor faults and unexpected behaviors. The features of the proposed observer are assessed by numerical and experimental data.

Monitoring bioreactors using principal component analysis: production of penicillin G acylase as a case study

The complexity of biological processes often makes impractical the development of detailed, structured phenomenological models of the cultivation of microorganisms in bioreactors. In this context, data pre-treatment techniques are useful for bioprocess control and fault detection. Among them, principal component analysis (PCA) plays an important role. This work presents a case study of the application of this technique during real experiments, where the enzyme penicillin G acylase (PGA) was produced by Bacillus megaterium ATCC 14945. PGA hydrolyzes penicillin G to yield 6-aminopenicilanic acid (6-APA) and phenyl acetic acid. 6-APA is used to produce semi-synthetic beta-lactam antibiotics. A static PCA algorithm was implemented for on-line detection of deviations from the desired process behavior. The experiments were carried out in a 2-L bioreactor. Hotteling's T(2) was the discrimination criterion employed in this multivariable problem and the method showed a high sensibility for fault detection in all real cases that were studied.

フロンティア研究シリーズ コロイド科学的手法による微生物の付着制御

The microbial adhesion is positively utilized for the immobilization of microorganisms in bioreactors although it causes troubles in medical implants and devices, food, metallic corrosion, pipeline, dental caries. Microbial adhesion is inevitable when solid surfaces are exposed to an aqueous phase. However, the mechanism of microbial adhesion to solid surface has not been well understood. In this paper, the interactions between microorganisms and solid surfaces are briefly reviewed. From the viewpoint of the colloid science, the measurements of the microbial surface characteristics, analysis of the microbial adhesion and its application are introduced.

Bioflocculation as a microbial response to substrate limitations

Previous theories of nutrient supply to microbial floes assumed that transport within the flocs was by molecular diffusion, and they predict that overall nutrient uptake is reduced in floes compared to dispersed cells. Calculations, supported by recent advances in understanding fluid flow through suspended aggregates, however, have shown that substantial fluid flow may occur through highly permeable bacterial floes. Since bioflocculation of microorganisms in bioreactors is known to occur under conditions of low substrate availability, the rate of substrate uptake is assumed to be mass transfer limited. The hydrodynamic environment of a cell then determines cellular uptake rates. Through development of a relative uptake factor, the overall uptake by cells in flocs in sheared fluids and floes attached to bubbles are compared with the uptake by an identical quantity of dispersed cells. Bioflocculation is found to increase the rate of substrate transport to cells in permeable floes compared to dispersed cells, particularly for large-molecular-weight substrates and when bubbles are present.