Model-Based Fault Diagnosis and Fault Tolerant Control for Safety-Critical Chemical Reactors: A Case Study of an Exothermic Continuous Stirred-Tank Reactor
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SUBMITTER: Du P
PROVIDER: S-EPMC10862546 | biostudies-literature | 2023 Aug
REPOSITORIES: biostudies-literature
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Project description:This study attempted to compare the enrichment of complete ammonium oxidation (comammox) bacteria, which are affiliated with Nitrospira and not able to generate nitrous oxide (N2O, a potent greenhouse gas) through biological pathways, in two commonly-utilized configurations of floccular sludge reactors, i.e., sequencing batch reactor (SBR) and continuous stirred tank reactor (CSTR), under the ammonium condition of mainstream wastewater (i.e., 40.0 g-N/m3). The results in terms of nitrification performance and microbial analyses during 216-d operation showed that compared with SBR offering a fluctuating but generally higher in-situ ammonium concentration (i.e., 1.0-6.0 g-N/m3) which was favorable for the growth of ammonium-oxidizing bacteria (AOB, belonging to Nitrosomonas in this study), CSTR managed to lower the in-situ ammonium level to < 2.0 g-N/m3, thus creating a competitive advantage for comammox bacteria with a highly oligotrophic lifestyle. Such an argument was further supported by dedicated batch tests which revealed that Nitrospira-dominant sludge had a lower maximum ammonium oxidation rate and lower apparent ammonium and oxygen affinity constants than Nitrosomonas-dominant sludge (i.e., 33.5 ± 2.1 mg-N/h/g-MLVSS vs. 139.9 ± 26.7 mg-N/h/g-MLVSS, 1.1 ± 0.1 g-N/m3 vs. 17.6 ± 4.6 g-N/m3, and 0.017 ± 0.002 g-O2/m3 vs. 0.037 ± 0.013 g-O2/m3, respectively), proving the nature of comammox bacteria as a K-strategist. Overall, this study not only provided useful insights into the effective enrichment of comammox bacteria in floccular sludge but also further revealed the interactions between comammox bacteria and AOB, thereby contributing to the future development of comammox-inclusive biological nitrogen removal technologies for sustainable wastewater treatment.
| S-EPMC11802381 | biostudies-literature
Project description:Nitrite-oxidizing bacteria are vital players in the global nitrogen cycle that convert nitrite to nitrate during the 2nd step of nitrification. Within this functional guild, the genus Nitrospira is among the most widespread and phylogenetically and physiologically diverse nitrite oxidizers and its members drive nitrite oxidation in many natural and biotechnological ecosystems. Despite their ecological and biotechnological importance, our understanding of Nitrospira’s energy metabolism is still limited. The main bottleneck for a detailed biochemical characterization of Nitrospira is biomass production, since they are slow-growing organisms and fastidious to culture. In this study, we cultured Nitrospira moscoviensis in a continuous stirred tank reactor system (CSTR) allowing constant biomass harvesting. Additionally, this cultivation setup enabled accurate control of physicochemical parameters and thus avoided fluctuating levels of nitrite and accumulation of nitrate. We performed transcriptome analysis and confirmed constant gene expression profiles in the chemostat culture over a period of two weeks. The transcriptomic data supports the predicted core metabolism of N. moscoviensis, including the reductive TCA cycle as a CO2 fixation pathway, the novel bd-like oxidase as terminal oxidase and the octaheme nitrite reductase involved in nitrogen assimilation. Additionally, the expression of multiple copies of respiratory complexes suggests functional differentiation of these copies within the respiratory chain. Transcriptome analysis also suggests a soluble and a membrane-bound gamma subunit as part of the nitrite oxidoreductase (NXR), the enzyme catalyzing nitrite oxidation. Overall, the transcriptome data provided novel insights into the metabolism of Nitrospira supporting the genome-based prediction of key pathways. Moreover, the application of a CSTR to cultivate Nitrospira is an important foundation for future proteomic and biochemical characterizations, which are crucial for a better understanding of canonical and complete nitrifying microorganisms.
2019-07-03 | GSE123406 | GEO
Project description:Unfortunately, the major group of the systems in industry has nonlinear behavior and control of such processes with conventional control approaches with fixed parameters causes problems and suboptimal or unstable control results. An adaptive control is one way to how we can cope with nonlinearity of the system. This contribution compares classic adaptive control and its modification with Wiener system. This configuration divides nonlinear controller into the dynamic linear part and the static nonlinear part. The dynamic linear part is constructed with the use of polynomial synthesis together with the pole-placement method and the spectral factorization. The static nonlinear part uses static analysis of the controlled plant for introducing the mathematical nonlinear description of the relation between the controlled output and the change of the control input. Proposed controller is tested by the simulations on the mathematical model of the continuous stirred-tank reactor with cooling in the jacket as a typical nonlinear system.
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Project description:Neurospora crassa has been utilized as a model organism for studying biological, regulatory, and circadian rhythms for over 50 years. These circadian cycles are driven at the molecular level by gene transcription events to prepare for environmental changes. N. crassa is typically found on woody biomass and is commonly studied on agar-containing medium which mimics its natural environment. We report a novel method for disrupting circadian gene transcription while maintaining light responsiveness in N. crassa when held in a steady metabolic state using bioreactors. The arrhythmic transcription of core circadian genes and downstream clock-controlled genes was observed in constant darkness (DD) as determined by reverse transcription-quantitative PCR (RT-qPCR). Nearly all core circadian clock genes were up-regulated upon exposure to light during 11hr light/dark cycle experiments under identical conditions. Our results demonstrate that the natural timing of the robust circadian clock in N. crassa can be disrupted in the dark when maintained in a consistent metabolic state. Thus, these data lead to a path for the production of industrial scale enzymes in the model system, N. crassa, by removing the endogenous negative feedback regulation by the circadian oscillator.
| S-EPMC4451529 | biostudies-literature
Project description:BackgroundCo-cultures and cell immobilization have been used for retaining biomass in a bioreactor, with the aim to improve the volumetric hydrogen productivity (QH2). Caldicellulosiruptor kronotskyensis is a strong cellulolytic species that possesses tāpirin proteins for attaching on lignocellulosic materials. C. owensensis has its reputation as a biofilm former. It was investigated whether continuous co-cultures of these two species with different types of carriers can improve the QH2.ResultsQH2 up to 30 ± 0.2 mmol L-1 h-1 was obtained during pure culture of C. kronotskyensis with combined acrylic fibres and chitosan. In addition, the yield of hydrogen was 2.95 ± 0.1 mol H2 mol-1 sugars at a dilution rate (D) of 0.3 h-1. However, the second-best QH2 26.4 ± 1.9 mmol L-1 h-1 and 25.4 ± 0.6 mmol L-1 h-1 were obtained with a co-culture of C. kronotskyensis and C. owensensis with acrylic fibres only and a pure culture of C. kronotskyensis with acrylic fibres, respectively. Interestingly, the population dynamics revealed that C. kronotskyensis was the dominant species in the biofilm fraction, whereas C. owensensis was the dominant species in the planktonic phase. The highest amount of c-di-GMP (260 ± 27.3 µM at a D of 0.2 h-1) were found with the co-culture of C. kronotskyensis and C. owensensis without a carrier. This could be due to Caldicellulosiruptor producing c-di-GMP as a second messenger for regulation of the biofilms under the high dilution rate (D) to prevent washout.ConclusionsThe cell immobilization strategy using a combination of carriers exhibited a promising approach to enhance the QH2. The QH2 obtained during the continuous culture of C. kronotskyensis with combined acrylic fibres and chitosan gave the highest QH2 among the pure culture and mixed cultures of Caldicellulosiruptor in the current study. Moreover, it was the highest QH2 among all cultures of Caldicellulosiruptor species studied so far.
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Project description:Monod and Logistic growth models have been widely used as basic equations to describe cell growth in bioprocess engineering. In the case of the Monod equation, the specific growth rate is governed by a limiting nutrient, with the mathematical form similar to the Michaelis-Menten equation. In the case of the Logistic equation, the specific growth rate is determined by the carrying capacity of the system, which could be growth-inhibiting factors (i.e., toxic chemical accumulation) other than the nutrient level. Both equations have been found valuable to guide us build unstructured kinetic models to analyze the fermentation process and understand cell physiology. In this work, we present a hybrid Logistic-Monod growth model, which accounts for multiple growth-dependent factors including both the limiting nutrient and the carrying capacity of the system. Coupled with substrate consumption and yield coefficient, we present the analytical solutions for this hybrid Logistic-Monod model in both batch and continuous stirred tank reactor (CSTR) culture. Under high biomass yield (Yx/s ) conditions, the analytical solution for this hybrid model is approaching to the Logistic equation; under low biomass yield condition, the analytical solution for this hybrid model converges to the Monod equation. This hybrid Logistic-Monod equation represents the cell growth transition from substrate-limiting condition to growth-inhibiting condition, which could be adopted to accurately describe the multi-phases of cell growth and may facilitate kinetic model construction, bioprocess optimization, and scale-up in industrial biotechnology.
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Project description:Syngas fermentation is one of the bets for the future sustainable biobased economies due to its potential as an intermediate step in the conversion of waste carbon to ethanol fuel and other chemicals. Integrated with gasification and suitable downstream processing, it may constitute an efficient and competitive route for the valorization of various waste materials, especially if systems engineering principles are employed targeting process optimization. In this study, a dynamic multi-response model is presented for syngas fermentation with acetogenic bacteria in a continuous stirred-tank reactor, accounting for gas-liquid mass transfer, substrate (CO, H2 ) uptake, biomass growth and death, acetic acid reassimilation, and product selectivity. The unknown parameters were estimated from literature data using the maximum likelihood principle with a multi-response nonlinear modeling framework and metaheuristic optimization, and model adequacy was verified with statistical analysis via generation of confidence intervals as well as parameter significance tests. The model was then used to study the effects of process conditions (gas composition, dilution rate, gas flow rates, and cell recycle) as well as the sensitivity of kinetic parameters, and multiobjective genetic algorithm was used to maximize ethanol productivity and CO conversion. It was observed that these two objectives were clearly conflicting when CO-rich gas was used, but increasing the content of H2 favored higher productivities while maintaining 100% CO conversion. The maximum productivity predicted with full conversion was 2 g·L-1 ·hr-1 with a feed gas composition of 54% CO and 46% H2 and a dilution rate of 0.06 hr-1 with roughly 90% of cell recycle.
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Project description:In the framework of the H2020 project CROCODILE, the recovery of Co from oxidized ores by reductive bioleaching has been studied. The objective was to reduce Fe(III) to Fe(II) to enhance the dissolution of Co from New-Caledonian limonitic laterites, mainly composed of goethite and Mn oxides. This study focused on the Fe(III) bioreduction which is a relevant reaction of this process. In the first step, biomass growth was sustained by aerobic bio-oxidation of elemental sulfur. In the second step, the biomass anaerobically reduced Fe(III) to Fe(II). The last step, which is not in the scope of this study, was the reduction of limonites and the dissolution of metals. This study aimed at assessing the Fe(III) bioreduction rate at 35°C with a microbial consortium composed predominantly of Sulfobacillus (Sb.) species as the iron reducers and Acidithiobacillus (At.) caldus. It evaluated the influence of the biomass concentration on the Fe(III) bioreduction rate and yield, both in batch and continuous mode. The influence of the composition of the growth medium on the bioreduction rate was assessed in continuous mode. A mean Fe(III) bioreduction rate of 1.7 mg·L-1·h-1 was measured in batch mode, i.e., 13 times faster than the abiotic control (0.13 mg·L-1·h-1). An increase in biomass concentrations in the liquid phase from 4 × 108 cells·mL-1 to 3 × 109 cells·mL-1 resulted in an increase of the mean Fe(III) bioreduction rate from 1.7 to 10 mg·L-1·h-1. A test in continuous stirred tank reactors at 35°C resulted in further optimization of the Fe(III) bioreduction rate which reached 20 mg·L-1·h-1. A large excess of nutrients enables to obtain higher kinetics. The determination of this kinetics is essential for the design of a reductive bioleaching process.
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Project description:The culture of human induced pluripotent stem cells (hiPSCs) at large scale becomes feasible with the aid of scalable suspension setups in continuously stirred tank reactors (CSTRs). Innovative monitoring options and emerging automated process control strategies allow for the necessary highly defined culture conditions. Next to standard process characteristics such as oxygen consumption, pH, and metabolite turnover, a reproducible and steady formation of hiPSC aggregates is vital for process scalability. In this regard, we developed a hiPSC-specific suspension culture unit consisting of a fully monitored CSTR system integrated into a custom-designed and fully automated incubator. As a step towards cost-effective hiPSC suspension culture and to pave the way for flexibility at a large scale, we constructed and utilized tailored miniature CSTRs that are largely made from three-dimensional (3D) printed polylactic acid (PLA) filament, which is a low-cost material used in fused deposition modelling. Further, the monitoring tool for hiPSC suspension cultures utilizes in situ microscopic imaging to visualize hiPSC aggregation in real-time to a statistically significant degree while omitting the need for time-intensive sampling. Suitability of our culture unit, especially concerning the developed hiPSC-specific CSTR system, was proven by demonstrating pluripotency of CSTR-cultured hiPSCs at RNA (including PluriTest) and protein level.
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