| 1. |
- Andersson, Christian, et al.
(författare)
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Maintaining high anaerobic succinic acid productivity by product removal
- 2010
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Ingår i: Bioprocess and biosystems engineering (Print). - : Springer Science and Business Media LLC. - 1615-7591 .- 1615-7605. ; 33:6, s. 711-718
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Tidskriftsartikel (refereegranskat)abstract
- During dual-phase fermentations using Escherichia coli engineered for succinic acid production, the productivity and viable cell concentration decrease as the concentration of succinic acid increases. The effects of succinic acid on the fermentation kinetics, yield, and cell viability were investigated by resuspending cells in fresh media after selected fermentation times. The cellular succinic acid productivity could be restored, but cell viability continuously decreased throughout the fermentations by up to 80% and subsequently the volumetric productivity was reduced. Omitting complex nutrients in the resuspension media had no significant effect on cellular succinate productivity and yield, although the viable cell concentration and thus the volumetric productivity was reduced by approximately 20%. By resuspending the cells, the amount of succinate produced during a 100-h fermentation was increased by more than 60%. The results demonstrate that by product removal succinic acid productivity can be maintained at high levels for extended periods of time.
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| 2. |
- Bäcklund, Emma, et al.
(författare)
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Cell engineering of Escherichia coli allows high cell density accumulation without fed-batch process control
- 2008
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Ingår i: Bioprocess and biosystems engineering (Print). - : Springer Science and Business Media LLC. - 1615-7591 .- 1615-7605. ; 31:1, s. 11-20
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Tidskriftsartikel (refereegranskat)abstract
- A set of mutations in the phosphoenolpyruvate:carbohydrate phosphotransferase system (PTS) was used to create Escherichia coli strains with a reduced uptake rate of glucose. This allows a growth restriction, which is controlled on cellular rather than reactor level, which is typical of the fed-batch cultivation concept. Batch growth of the engineered strains resulted in cell accumulation profiles corresponding to a growth rate of 0.78, 0.38 and 0.25 h(-1), respectively. The performance of the mutants in batch cultivation was compared to fed-batch cultivation of the wild type cell using restricted glucose feed to arrive at the corresponding growth profiles. Results show that the acetate production, oxygen consumption and product formation were similar, when a recombinant product was induced from the lacUV5 promoter. Ten times more cells could be produced in batch cultivation using the mutants without the growth detrimental production of acetic acid. This allows high cell density production without the establishment of elaborate fed-batch control equipment. The technique is suggested as a versatile tool in high throughput multiparallel protein production but also for increasing the number of experiments performed during process development while keeping conditions similar to the large-scale fed-batch performance.
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| 3. |
- Charoenrat, Theppanya, et al.
(författare)
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Oxygen-limited fed-batch process : an alternative control for Pichia pastoris recombinant protein processes
- 2005
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Ingår i: Bioprocess and biosystems engineering (Print). - : Springer Science and Business Media LLC. - 1615-7591 .- 1615-7605. ; 27:6, s. 399-406
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Tidskriftsartikel (refereegranskat)abstract
- An oxygen-limited fed-batch technique (OLFB) was compared to traditional methanol-limited fed-batch technique (MLFB) for the production of recombinant Thai Rosewood beta-glucosidase with Pichia pastoris. The degree of energy limitation, expressed as the relative rate of respiration (q(O)/q(O,max)), was kept similar in both the types of processes. Due to the higher driving force for oxygen transfer in the OLFB, the oxygen and methanol consumption rates were about 40% higher in the OLFB. The obligate aerobe P. pastoris responded to the severe oxygen limitation mainly by increased maintenance demand, measured as increased carbon dioxide production per methanol, but still somewhat higher cell density (5%) and higher product concentrations (16%) were obtained. The viability was similar, about 90-95%, in both process types, but the amount of total proteins released in the medium was much less in the OLFB processes resulting in substantially higher (64%) specific enzyme purity for input to the downstream processing.
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| 4. |
- Cimander, Christian, et al.
(författare)
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Bioprocess control from a multivariate process trajectory.
- 2004
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Ingår i: Bioprocess and biosystems engineering (Print). - : Springer Science and Business Media LLC. - 1615-7591 .- 1615-7605. ; 26:6, s. 401-411
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Tidskriftsartikel (refereegranskat)abstract
- A multivariate bioprocess control approach, capable of tracking a pre-set process trajectory correlated to the biomass or product concentration in the bioprocess is described. The trajectory was either a latent variable derived from multivariate statistical process monitoring (MSPC) based on partial least squares (PLS) modeling, or the absolute value of the process variable. In the control algorithm the substrate feed pump rate was calculated from on-line analyzer data. The only parameters needed were the substrate feed concentration and the substrate yield of the growth-limiting substrate. On-line near-infrared spectroscopy data were used to demonstrate the performance of the control algorithm on an Escherichia coli fed-batch cultivation for tryptophan production. The controller showed good ability to track a defined biomass trajectory during varying process dynamics. The robustness of the control was high, despite significant external disturbances on the cultivation and control parameters.
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| 5. |
- de Maré, Lena, et al.
(författare)
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Feeding strategies for E-coli fermentations demanding an enriched environment
- 2007
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Ingår i: Bioprocess and Biosystems Engineering. - : Springer Science and Business Media LLC. - 1615-7605 .- 1615-7591. ; 30:1, s. 13-25
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Tidskriftsartikel (refereegranskat)abstract
- The addition of a carbon nutrient feed to a fed-batch cultivation is often not enough to obtain satisfactory growth and/or production. In some cases, an additional feed with for example supplementary amino acids or complex media is required. This work presents the development of feeding strategies where more than one feed is required and the knowledge of the growth requirements is low. Simulations and cultivations with E. coli are shown using the proposed feed controllers which are based on a probing control concept. The strategies work well and they can be used to shorten the process development phase considerably.
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| 6. |
- de Maré, Lena, et al.
(författare)
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Probing control of glucose feeding in Vibrio cholerae cultivations
- 2003
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Ingår i: Bioprocess and Biosystems Engineering. - : Springer Science and Business Media LLC. - 1615-7605 .- 1615-7591. ; 25:4, s. 221-228
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Tidskriftsartikel (refereegranskat)abstract
- Infection with Vibrio cholerae is a significant problem in manydeveloping countries. Cultivation of Vibrio cholerae is used inproduction of CTB, which is a component in a cholera vaccine. Fed - batch cultivations with V. cholerae in defined mediahave been conducted and reproducible results were obtained. A probing feeding strategy developed by Åkessonfor E. coli cultivations has been tested.The program is working as well for V. cholerae as forE. coliin minimizing the amount acetic acid formed and avoiding anaerobicconditions. Two hours after the feed start most of the acetic acidaccumulated during the batch phase is consumed. The resulting feedrate tends to be thehighest possible with respect to the constraints from cell metabolismand mass transfer, thus maximizing productivity in terms of biomass.A cell dry weight of 20 - 23 g/l is obtained after12 hours of feeding.
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| 7. |
- Ekstrand, Eva-Maria, et al.
(författare)
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Viscosity dynamics and the production of extracellular polymeric substances and soluble microbial products during anaerobic digestion of pulp and paper mill wastewater sludges
- 2020
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Ingår i: Bioprocess and biosystems engineering (Print). - : SPRINGER. - 1615-7591 .- 1615-7605. ; 43:2, s. 283-291
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Tidskriftsartikel (refereegranskat)abstract
- The production processes of the pulp and paper industry often run in campaigns, leading to large variations in the composition of wastewaters and waste sludges. During anaerobic digestion (AD) of these wastes, the viscosity or the production of extracellular polymeric substances (EPS) and soluble microbial products (SMP) may be affected, with the risk of foam formation, inefficient digester mixing or poor sludge dewaterability. The aim of this study was to investigate how viscosity and production of EPS and SMP during long-term AD of pulp and paper mill sludge is affected by changes in organic loading rate (OLR) and hydraulic retention time (HRT). Two mesophilic lab-scale continuous stirred tank reactors (CSTRs) were operated for 800 days (R1 and R2), initially digesting only fibre sludge, then co-digesting fibre sludge and activated sludge. The HRT was lowered, followed by an increase in the OLR. Reactor fluids were sampled once a month for rheological characterization and analysis of EPS and SMP. The production of the protein fraction of SMP was positively correlated to the OLR, implicating reduced effluent qualities at high OLR. EPS formation correlated with the magnesium content, and during sulphate deficiency, the production of EPS and SMP increased. At high levels of EPS and SMP, there was an increase in viscosity of the anaerobic sludges, and dewatering efficiency was reduced. In addition, increased viscosity and/or the production of EPS and SMP were important factors in sludge bulking and foam formation in the CSTRs. Sludge bulking was avoided by more frequent stirring.
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| 8. |
- Gustavsson, Robert, et al.
(författare)
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Soft sensor control of metabolic fluxes in a recombinant Escherichia coli fed-batch cultivation producing green fluorescence protein
- 2013
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Ingår i: Bioprocess and biosystems engineering (Print). - : Springer Verlag (Germany). - 1615-7591 .- 1615-7605. ; 36:10, s. 1375-1384
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Tidskriftsartikel (refereegranskat)abstract
- A soft sensor approach is described for controlling metabolic overflow from mixed-acid fermentation and glucose overflow metabolism in a fed-batch cultivation for production of recombinant green fluorescence protein (GFP) in Escherichia coli. The hardware part of the sensor consisted of a near-infrared in situ probe that monitored the E. coli biomass and an HPLC analyzer equipped with a filtration unit that measured the overflow metabolites. The computational part of the soft sensor used basic kinetic equations and summations for estimation of specific rates and total metabolite concentrations. Two control strategies for media feeding of the fed-batch cultivation were evaluated: (1) controlling the specific rates of overflow metabolism and mixed-acid fermentation metabolites at a fixed pre-set target values, and (2) controlling the concentration of the sum of these metabolites at a set level. The results indicate that the latter strategy was more efficient for maintaining a high titer and low variability of the produced recombinant GFP protein.
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| 9. |
- Han, L., et al.
(författare)
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Escherichia coli high-cell-density culture : carbon mass balances and release of outer membrane components
- 2003
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Ingår i: Bioprocess and biosystems engineering (Print). - : Springer Science and Business Media LLC. - 1615-7591 .- 1615-7605. ; 25:4, s. 205-212
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Tidskriftsartikel (refereegranskat)abstract
- Carbon mass balances were calculated in fed-batch cultures of E. coli W3110, using mineral medium with glucose as the limiting substrate. The carbon recovery, based on biomass, CO2 and acetate was similar to90% at the end of the culture (25 h, 27 g L-1 dw). The missing carbon remained as soluble organic compounds in the medium. Outer membrane (OM) constituents, such as lipopolysaccharides (LPS), phospholipids (PL), and carbohydrates (each at similar to1 g L-1) contributed to 63% of the extracellular carbon. The amount of released LPS and PL equaled the total amount of OM bound to the cells in the culture. Small amounts of DNA and protein detected in the medium indicated that no cell lysis had occurred. Acetate, lactate, ethanol, formate, succinate and amino acids (Glu, Gln, Asp, Asn, Ala, Gly, Ser) were detected in the culture medium, but made up only a few percent of the carbon mass. The remaining 30% was not identified, but was assumed to constitute complex carbohydrates.
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| 10. |
- Hernández-Ibáñez, N., et al.
(författare)
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Effect of confinement of horse heart cytochrome c and formate dehydrogenase from Candida boidinii on mesoporous carbons on their catalytic activity
- 2021
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Ingår i: Bioprocess and biosystems engineering (Print). - : Springer Science and Business Media Deutschland GmbH. - 1615-7591 .- 1615-7605. ; 44:8, s. 1699-1710
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Tidskriftsartikel (refereegranskat)abstract
- This study reports the immobilization of two biocatalysts (e.g., cytochrome c—Cyt c—and the non-metalloenzyme formate dehydrogenase from Candida boidinii–cbFDH) on a series of mesoporous carbons with controlled pore sizes. The catalytic activity of the nanoconfined proteins was correlated with the pore size distribution of the carbon materials used as supports. The electrochemical behaviour of nanoconfined Cyt c showed direct electron transfer electroactivity in pore sizes matching tightly the protein dimension. The pseudo-peroxidase activity towards H2O2 reduction was enhanced at pH 4.0, due to the protein conformational changes. For cbFDH, the reduction of CO2 towards formic acid was evaluated for the nanoconfined protein, in the presence of nicotinamide adenine dinucleotide (NADH). The carbons displayed different cbFDH uptake capacity, governed by the dimensions of the main mesopore cavities and their accessibility through narrow pore necks. The catalytic activity of nanoconfined cbFDH was largely improved, compared to its performance in free solution. Regardless of the carbon support used, the production of formic acid was higher upon immobilization with lower nominal cbFDH:NADH ratios.
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