•A nonlinear model predictive control scheme for fed-batch bioreactors is developed.•The scheme utilizes a dynamic flux balance model for control calculations.•Feedback is implemented through state ...resetting over a shrinking control horizon.•Simulations show 8–15% ethanol production increases compared to open-loop control.
Fed-batch fermentation is an important production technology in the biochemical industry. Using fed-batch Saccharomyces cerevisiae fermentation as a prototypical example, we developed a general methodology for nonlinear model predictive control of fed-batch bioreactors described by dynamic flux balance models. The control objective was to maximize ethanol production at a fixed final batch time by adjusting the glucose feeding rate and the aerobic–anaerobic switching time. Effectiveness of the closed-loop implementation was evaluated by comparing the relative performance of NMPC and the open-loop optimal controller. NMPC was able to compensate for structural errors in the intracellular model and parametric errors in the substrate uptake kinetics and cellular energetics by increasing ethanol production between 8.0% and 14.7% compared with the open-loop operating policy. Minimal degradation in NMPC performance was observed when the biomass, glucose, and ethanol concentration and liquid volume measurements were corrupted with Gaussian white noise. NMPC based on the dynamic flux balance model was shown to improve ethanol production compared to the same NMPC formulation based on a simpler unstructured model. To our knowledge, this study represents the first attempt to utilize a dynamic flux balance model within a nonlinear model-based control scheme.
Two CHO cell clones derived from the same parental CHO
BC®
cell line and producing the same monoclonal antibody (BC-G, a low producing clone; BC-P, a high producing clone) were tested in four basal ...media in all possible combinations with three feeds (=12 conditions) in fed-batch cultures. Higher amino acid feeding did not always lead to higher mAb production. The two clones showed differences in cell physiology, metabolism and optimal medium-feed combinations. During the phase transitions of all cultures, cell metabolism showed a shift represented by lower specific consumption and production rates, except for the specific glucose consumption rate in cultures fed by Actifeed A/B. The BC-P clone fed by Actifeed A/B showed a threefold cell volume increase and an increase of the specific consumption rate of glucose in the stationary phase. Since feeding was based on glucose this resulted in accumulation of amino acids for this feed, while this did not occur for the poorer feed (EFA/B). The same feed also led to an increase of cell size for the BC-G clone, but to a lesser extent.
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•We achieved CaCO3 precipitation yields up to 18.9gCaCO3/gNO3-N in 2 days.•Repetitive CaCO3 precipitation can be achieved from single inoculation.•Precipitation formed around the ...cells decreases nutrient uptake rate and activity.•Denitrifiers removed Ca2+ from paper mill wastewater through CaCO3 precipitation.
So far, researchers investigated microbially induced CaCO3 precipitation (MICP) for soil reinforcement, self-repairing concrete and Ca2+ removal from industrial waste streams. Reported MICP yields were mainly achieved under nutrient-rich conditions. However, creating the tested nutrient-rich conditions in intended applications is both an economical and a practical issue. Therefore, investigation of MICP in more realistic conditions is necessary. This study presents optimization of MICP through denitrification in minimal nutrient conditions. To optimize their MICP performances, we isolated two strains, Pseudomonas aeruginosa and Diaphorobacter nitroreducens, by following an application oriented selection procedure. Upon performance optimization, in 2 days, D. nitroreducens and P. aeruginosa precipitated 14.1 and 18.9gCaCO3/gNO3-N, respectively. Repetitive CaCO3 precipitation was also achieved from a single inoculum in both 2 days and 3 weeks intervals. Selected strains and the process were further evaluated for three MICP applications: (1) Ca2+ removal from paper mill wastewater (2) soil reinforcement, (3) crack repair in concrete. Overall, denitrification was found to be an effective process to remove Ca2+ from paper mill wastewater. P. aeruginosa and D. nitroreducens could be introduced as potential candidates for soil and concrete applications due to their enhanced precipitation yields, resilience and performance under minimal nutrient conditions.
Model‐based online optimization has not been widely applied to bioprocesses due to the challenges of modeling complex biological behaviors, low‐quality industrial measurements, and lack of ...visualization techniques for ongoing processes. This study proposes an innovative hybrid modeling framework which takes advantages of both physics‐based and data‐driven modeling for bioprocess online monitoring, prediction, and optimization. The framework initially generates high‐quality data by correcting raw process measurements via a physics‐based noise filter (a generally available simple kinetic model with high fitting but low predictive performance); then constructs a predictive data‐driven model to identify optimal control actions and predict discrete future bioprocess behaviors. Continuous future process trajectories are subsequently visualized by re‐fitting the simple kinetic model (soft sensor) using the data‐driven model predicted discrete future data points, enabling the accurate monitoring of ongoing processes at any operating time. This framework was tested to maximize fed‐batch microalgal lutein production by combining with different online optimization schemes and compared against the conventional open‐loop optimization technique. The optimal results using the proposed framework were found to be comparable to the theoretically best production, demonstrating its high predictive and flexible capabilities as well as its potential for industrial application.
A innovative model‐based bioprocess online optimization technique is proposed to tackle on the challenges of modeling complex biological behaviors, low‐quality industrial measurements, and lack of visualization techniques for ongoing processes.
Pullulanase is a debranching enzyme that cleaves explicitly α-1,6 glycosidic bonds, which is widely used in starch saccharification, production of glucose, maltose, and bioethanol. The ...thermal-resistant pullulanase is isolated from a variety of microorganisms; however, the lack of industrial production of pullulanase has hindered the transformation of the laboratory to industry. In this study, the expensive maltose syrup and soybean meal powder were replaced with cheap corn starch and corn steep liquor, exhibiting 440 U/mL of pullulanase in shake flasks by changing the C/N value and the total energy of the medium. Subsequently, the cultivation conditions were explored in a 50-L and 50-m
3
bioreactor. In batch culture, the pullulanase activity reached 896 U/mL, while it increased to 1743 U/mL in fed-batch culture by controlling the dissolved oxygen, pH, reducing sugar content, and temperature. Remarkably, the cultivation volume was enlarged to 50 m
3
based on the technical parameters of fed-batch culture. The industrial production of pullulanase was successful, and the activity achieved 1546 U/mL. When the product was stored at room temperature (25 °C) for 6 months, the pullulanase activity was over 90%. The half-lives at 60 and 80 °C were 119.45 h and 51.18 h, respectively, which satisfied the industrial application requirements of pullulanase.
The present study addresses the synthesis and properties of polyhydroxyalkanoates (PHA) of different composition synthesized by
Cupriavidus eutrophus
B-10646 using glycerol as a carbon substrate. ...Poly(3-hydroxybutyrate) P(3HB) was effectively synthesized in fed-batch culture in a 30-L fermenter on glycerol of various purification degrees, with 99.5, 99.7, and 82.1% content of the main component. Purified glycerol (99.7%) was used for 150-L pilot scale fermentation. The total biomass and P(3HB) concentration reached 110 and 85.8 g/L, respectively, after 45 h of fed-batch fermentation. An average volumetric productivity of P(3HB) was 1.83 g/(L h). The degree of crystallinity and molecular weight of P(3HB) synthesized on glycerol were lower than and temperature characteristics were the same as those of P(3HB) synthesized on sugars.
The microbial product citramalic acid (citramalate) serves as a five‐carbon precursor for the chemical synthesis of methacrylic acid. This biochemical is synthesized in Escherichia coli directly by ...the condensation of pyruvate and acetyl‐CoA via the enzyme citramalate synthase. The principal competing enzyme with citramalate synthase is citrate synthase, which mediates the condensation reaction of oxaloacetate and acetyl‐CoA to form citrate and begin the tricarboxylic acid cycle. A deletion in the gltA gene coding citrate synthase prevents acetyl‐CoA flux into the tricarboxylic acid cycle, and thus necessitates the addition of glutamate. In this study the E. coli citrate synthase was engineered to contain point mutations intended to reduce the enzyme's affinity for acetyl‐CoA, but not eliminate its activity. Cell growth, enzyme activity and citramalate production were compared in several variants in shake flasks and controlled fermenters. Citrate synthase GltAF383M not only facilitated cell growth without the presence of glutamate, but also improved the citramalate production by 125% compared with the control strain containing the native citrate synthase in batch fermentation. An exponential feeding strategy was employed in a fed‐batch process using MEC626/pZE12‐cimA harboring the GltAF383M variant, which generated over 60 g/L citramalate with a yield of 0.53 g citramalate/g glucose in 132 hr. These results demonstrate protein engineering can be used as an effective tool to redirect carbon flux by reducing enzyme activity and improve the microbial production of traditional commodity chemicals.
Biosynthesis of citramalate in Escherichia coli expressing the cimA gene coding citramalate synthase. A reduction in the activity of citrate synthase through the integration of single residue variants increases the availability of acetyl‐CoA and citramalate formation.
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•Phosphorus depletion had no influence on lipid accumulation.•Glucose inhibition was comparatively investigated with osmotic inhibition.•Nitrogen depletion and hyperosmotic stress ...enhanced lipid accumulation.•A novel two-stage fed-batch culture enhanced the lipid production.
In this study, the influences of major nutrients on cell growth and lipid production were investigated in heterotrophic culture of Chlorella protothecoides. The results demonstrated that phosphorus depletion had no effect on lipid accumulation but restricted cell growth; however, nitrogen depletion could enhance lipid accumulation thus benefiting lipid production. Furthermore, the effects of glucose inhibition were comparatively investigated with osmotic stress, showing that the effects of glucose inhibition were similar to the effect of osmotic stress at equivalent osmotic pressures only if the glucose concentration was less than 100g/L, otherwise the effects of glucose inhibition became much stronger than osmotic stress. Interestingly, it was found that a specific hyperosmotic stress could significantly enhance lipid accumulation, thus providing a new stress strategy for efficient lipid production. Finally, a novel two-stage fed-batch culture consisting of a growth phase and a lipid accumulation phase with nitrogen depletion and hyperosmotic stress was proposed, yielding a final lipid productivity of 177.3mg/L/h with a very high lipid yield of 207.0mg/g glucose and lipid content of 39.2% after 180 h culture, which were 1.60, 1.79 and 1.92-fold of those obtained in one-stage fed-batch culture without stress phase, respectively.
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