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Glauche F, Glazyrina J, Cruz Bournazou MN, Kiesewetter G, Cuda F, Goelling D, Raab A, Lang C, Neubauer P. Detection of growth rate-dependent product formation in miniaturized parallel fed-batch cultivations. Eng Life Sci 2017; 17:1215-1220. [PMID: 32624749 PMCID: PMC6999230 DOI: 10.1002/elsc.201600029] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2016] [Revised: 04/28/2017] [Accepted: 07/24/2017] [Indexed: 12/22/2022] Open
Abstract
Saccharomyces cerevisiae is a popular expression system for recombinant proteins. In most cases, production processes are performed as carbon-limited fed-batch cultures to avoid aerobic ethanol formation. Especially for constitutive expression systems, the specific product formation rate depends on the specific growth rate. The development of optimal feeding strategies strongly depends on laboratory-scale cultivations, which are time and resource consuming, especially when continuous experiments are carried out. It is therefore beneficial for accelerated process development to look at alternatives. In this study, S. cerevisiae AH22 secreting a heterologous endo-polygalacturonase (EPG) was characterized in microwell plates with an enzyme-based fed-batch medium. Through variation of the glucose release rate, different growth profiles were established and the impact on EPG secretion was analyzed. Product formation rates of 200-400 U (gx h)-1 were determined. As a reference, bioreactor experiments using the change-stat cultivation technique were performed. The growth-dependent product formation was analyzed over dilution rates of D = 0.01-0.35 with smooth change of D at a rate of 0.003 h-2. EPG production was found to be comparable with a qp of 400 U (gx h)-1 at D = 0.27 h-1. The presented results indicate that parallel miniaturized fed-batch cultures can be applied to determine product formation profiles of putative production strains. With further automation and parallelization of the concept, strain characterization can be performed in shorter time.
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Affiliation(s)
- Florian Glauche
- Chair of Bioprocess EngineeringTechnische Universität BerlinBerlinGermany
| | - Julia Glazyrina
- Chair of Bioprocess EngineeringTechnische Universität BerlinBerlinGermany
| | | | | | - Fabian Cuda
- Chair of Bioprocess EngineeringTechnische Universität BerlinBerlinGermany
| | | | | | | | - Peter Neubauer
- Chair of Bioprocess EngineeringTechnische Universität BerlinBerlinGermany
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2
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Schmacht M, Lorenz E, Stahl U, Senz M. Medium optimization based on yeast's elemental composition for glutathione production in Saccharomyces cerevisiae. J Biosci Bioeng 2017; 123:555-561. [DOI: 10.1016/j.jbiosc.2016.12.011] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2016] [Revised: 12/13/2016] [Accepted: 12/15/2016] [Indexed: 01/27/2023]
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3
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Adamberg K, Valgepea K, Vilu R. Advanced continuous cultivation methods for systems microbiology. Microbiology (Reading) 2015. [DOI: 10.1099/mic.0.000146] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Affiliation(s)
- Kaarel Adamberg
- Tallinn University of Technology, Department of Food Processing, Ehitajate tee 5, 19086 Tallinn, Estonia
- Competence Center of Food and Fermentation Technologies, Akadeemia tee 15a, 12618 Tallinn, Estonia
| | - Kaspar Valgepea
- Competence Center of Food and Fermentation Technologies, Akadeemia tee 15a, 12618 Tallinn, Estonia
| | - Raivo Vilu
- Competence Center of Food and Fermentation Technologies, Akadeemia tee 15a, 12618 Tallinn, Estonia
- Tallinn University of Technology, Department of Chemistry, Akadeemia tee 15, 12618 Tallinn, Estonia
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4
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Gabardo S, Pereira GF, Rech R, Ayub MAZ. The modeling of ethanol production by Kluyveromyces marxianus using whey as substrate in continuous A-Stat bioreactors. J Ind Microbiol Biotechnol 2015; 42:1243-53. [PMID: 26233317 DOI: 10.1007/s10295-015-1661-2] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2015] [Accepted: 07/23/2015] [Indexed: 10/23/2022]
Abstract
We investigated the kinetics of whey bioconversion into ethanol by Kluyveromyces marxianus in continuous bioreactors using the "accelerostat technique" (A-stat). Cultivations using free and Ca-alginate immobilized cells were evaluated using two different acceleration rates (a). The kinetic profiles of these systems were modeled using four different unstructured models, differing in the expressions for the specific growth (μ) and substrate consumption rates (r s), taking into account substrate limitation and product inhibition. Experimental data showed that the dilution rate (D) directly affected cell physiology and metabolism. The specific growth rate followed the dilution rate (μ≈D) for the lowest acceleration rate (a = 0.0015 h(-2)), condition in which the highest ethanol yield (0.52 g g(-1)) was obtained. The highest acceleration rate (a = 0.00667 h(-2)) led to a lower ethanol yield (0.40 g g(-1)) in the system where free cells were used, whereas with immobilized cells ethanol yields increased by 23 % (0.49 g g(-1)). Among the evaluated models, Monod and Levenspiel combined with Ghose and Tyagi models were found to be more appropriate for describing the kinetics of whey bioconversion into ethanol. These results may be useful in scaling up the process for ethanol production from whey.
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Affiliation(s)
- Sabrina Gabardo
- Biotechnology and Biochemical Engineering Laboratory (BiotecLab), Federal University of Rio Grande do Sul, Av. Bento Gonçalves, 9500, PO Box 15090, Porto Alegre, RS, 91501-970, Brazil
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Abstract
Lab-scale stirred-tank bioreactors (0.2-20 l) are used for fundamental research on animal cells and in process development and troubleshooting for large-scale production. In this chapter, different configurations of bioreactor systems are shortly discussed and setting up these different configurations is described. In addition, online measurement and control of bioreactor parameters is described, with special attention to controller settings (PID) and online measurement of oxygen consumption and carbon dioxide production. Finally, methods for determining the oxygen transfer coefficient are described.
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Affiliation(s)
- Dirk E Martens
- Bioprocess Engineering, Wageningen University, Wageningen, The Netherlands,
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6
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Hoekema S, Rinzema A, Tramper J, Wijffels RH, Janssen M. Deceleration-stats save much time during phototrophic culture optimization. Biotechnol Bioeng 2013; 111:792-802. [DOI: 10.1002/bit.25131] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2013] [Accepted: 10/02/2013] [Indexed: 11/09/2022]
Affiliation(s)
- Sebastiaan Hoekema
- Bioprocess Engineering; Wageningen University; P.O. Box 8129 6700 EV Wageningen The Netherlands
| | - Arjen Rinzema
- Bioprocess Engineering; Wageningen University; P.O. Box 8129 6700 EV Wageningen The Netherlands
| | - Johannes Tramper
- Bioprocess Engineering; Wageningen University; P.O. Box 8129 6700 EV Wageningen The Netherlands
| | - René H. Wijffels
- Bioprocess Engineering; Wageningen University; P.O. Box 8129 6700 EV Wageningen The Netherlands
| | - Marcel Janssen
- Bioprocess Engineering; Wageningen University; P.O. Box 8129 6700 EV Wageningen The Netherlands
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7
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Hoekema S, van Breukelen FR, Janssen M, Tramper J, Wijffels RH. Exploration of the hydrogen producing potential of Rhodobacter capsulatus chemostat cultures: The application of deceleration-stat and gradient-stat methodology. Biotechnol Prog 2009; 25:1343-52. [PMID: 19626702 DOI: 10.1002/btpr.196] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
In this work, the dependency of the volumetric hydrogen production rate of ammonium-limited Rhodobacter capsulatus chemostat cultures on their imposed biomass concentration and dilution rate was investigated. A deceleration-stat experiment was performed by lowering the dilution rate from 1.0 d(-1) to zero aimed at a constant biomass concentration of 4.0 g L(-1) at constant incident light intensity. The results displayed a maximal volumetric hydrogen production rate of 0.6 mmol m(-3) s(-1), well below model predictions. Possibly the high cell density limited the average light availability, resulting in a sub-optimal specific hydrogen production rate. To investigate this hypothesis, a gradient-stat experiment was conducted at constant dilution rate of 0.4 d(-1) at constant incident light intensity. The biomass concentration was increased from 0.7 to 4.0 g L(-1) by increasing the influent ammonium concentration. Up to a biomass concentration of 1.5 g L(-1), the volumetric hydrogen production rate of the system increased according to model predictions, after which it started to decline. The results obtained provide strong evidence that the observed decline in volumetric hydrogen production rate at higher biomass concentrations was at least partly caused by a decrease in light availability.
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Lahtvee PJ, Valgepea K, Nahku R, Abner K, Adamberg K, Vilu R. Steady state growth space study of Lactococcus lactis in D-stat cultures. Antonie Van Leeuwenhoek 2009; 96:487-96. [PMID: 19603284 DOI: 10.1007/s10482-009-9363-2] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2009] [Accepted: 06/24/2009] [Indexed: 10/20/2022]
Abstract
Growth space of Lactococcus lactis subsp. lactis IL1403 was studied at constant growth rate using D-stat cultivation technique. Starting from steady state conditions in a chemostat culture (mu = 0.2 h(-1)), the pH and/or temperature were continuously changed in the range of 5.4-6.4 and 26-34 degrees C, respectively, followed by the return to the initial environmental conditions. Based on substrate consumption and product formation yields and expression changes of 1,920 genes, it was shown that changes of physiological state were not dependent on the direction of movement (from pH 6.3 to 5.4 or from 5.4 to 6.3), showing that quasi steady state values in D-stat corresponded to the steady state values in chemostats. Relative standard deviation of growth characteristics in triplicate D-stat experiments was below 10%. Continuing the experiment and reestablishing initial growth conditions revealed in average 7% difference (hysteresis) in growth characteristics when comparing chemostat steady state cultures prior and after the change of environmental conditions. Similarly, shifts were also seen at gene expression levels. The large amount of quantitatively reliable data obtained in this study provided a new insight into dynamic properties of bacterial physiology, and can be used for describing the growth space of microorganisms by modeling cell metabolism.
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Affiliation(s)
- Petri-Jaan Lahtvee
- Department of Chemistry, Tallinn University of Technology, Akadeemia tee 15, 12618 Tallinn, Estonia
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9
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Adamberg K, Lahtvee PJ, Valgepea K, Abner K, Vilu R. Quasi steady state growth of Lactococcus lactis in glucose-limited acceleration stat (A-stat) cultures. Antonie van Leeuwenhoek 2009; 95:219-26. [PMID: 19184516 DOI: 10.1007/s10482-009-9305-z] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/13/2007] [Accepted: 01/09/2009] [Indexed: 11/29/2022]
Abstract
Quasi steady state growth of Lactococcus lactis IL 1403 was studied in glucose-limited A-stat cultivation experiments with acceleration rates (a) from 0.003 to 0.06 h(-2) after initial stabilization of the cultures in chemostat at D = 0.2-0.3 h(-1). It was shown that the high limit of quasi steady state growth rate depended on the acceleration rate used-at an acceleration rate 0.003 h(-2) the quasi steady state growth was observed until mu (crit) = 0.59 h(-1), which is also the mu (max) value for the culture. Lower values of mu (crit) were observed at higher acceleration rates. The steady state growth of bacteria stabilized at dilution rate 0.2 h(-1) was immediately disrupted after initiating acceleration at the highest acceleration rate studied-0.06 h(-2). Observation was made that differences [Delta(mu - D)] of the specific growth rates from pre-programmed dilution rates were the lowest using an acceleration rate of 0.003 h(-2) (< 4% of preset changing growth rate). The adaptability of cells to follow preprogrammed growth rate was found to decrease with increasing dilution rate-it was shown that lower acceleration rates should be applied at higher growth rates to maintain the culture in the quasi steady state. The critical specific growth rate and the biomass yields based on glucose consumption were higher if the medium contained S (0) = 5 g L(-1) glucose instead of S (0) = 10 g L(-1). It was assumed that this was due to the inhibitory effect of lactate accumulating at higher concentrations in the latter cultures. Parallel A-stat experiments at the same acceleration and dilution rates showed good reproducibility-Delta(mu - D) was less than 5%, standard deviations of biomass yields per ATP produced (Y (ATP)), and biomass yields per glucose consumed (Y (XS)) were less than 15%.
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Affiliation(s)
- Kaarel Adamberg
- Department of Food Processing, Tallinn University of Technology, Ehitajate tee 5, Tallinn, Estonia
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Kasemets K, Nisamedtinov I, Laht TM, Abner K, Paalme T. Growth characteristics of Saccharomyces cerevisiae S288C in changing environmental conditions: auxo-accelerostat study. Antonie van Leeuwenhoek 2007; 92:109-28. [PMID: 17268890 DOI: 10.1007/s10482-007-9141-y] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/17/2006] [Accepted: 01/04/2007] [Indexed: 11/26/2022]
Abstract
The effect of individual environmental conditions (pH, pO(2), temperature, salinity, concentration of ethanol, propanol, tryptone and yeast extract) on the specific growth rate as well as ethanol and glycerol production rate of Saccharomyces cerevisiae S288C was mapped during the fermentative growth in aerobic auxo-accelerostat cultures. The obtained steady-state values of the glycerol to ethanol formation ratio (0.1 mol mol(-1)) corresponding to those predicted from the stoichiometric model of fermentative yeast growth showed that the complete repression of respiration was obtained in auxostat culture and that the model is suitable for calculation of Y(ATP) and Q(ATP) values for the aerobic fermentative growth. Smooth decrease in the culture pH and dissolved oxygen concentration (pO2) down to the critical values of 2.3 and 0.8%, respectively, resulted in decrease in growth yield (Y(ATP)) and specific growth rate, however the specific ATP production rate (Q(ATP)) stayed almost constant. Increase in the concentration of biomass (>0.8 g dwt l(-1)), propanol (>2 g l(-1)) or NaCl (>15 g l(-1)) lead at first to the decrease in the specific growth rate and Q(ATP), while Y(ATP) was affected only at higher concentrations. The observed decrease in Q(ATP) was caused by indirect rather than direct inhibition of glycolysis. The increase in tryptone concentration resulted in an increase in the specific growth rate from 0.44 to 0.62 h(-1) and Y(ATP) from 12.5 to 18.5 mol ATP g dwt(-1). This study demonstrates that the auxo-accelerostat method, besides being an efficient tool for obtaining the culture characteristics, provides also decent conditions for the experiments elucidating the control mechanisms of cell growth.
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Affiliation(s)
- Kaja Kasemets
- National Institute of Chemical Physics and Biophysics, Akadeemia tee 23, 12618, Tallinn, Estonia
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11
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Jansen MLA, Krook DJJ, De Graaf K, van Dijken JP, Pronk JT, de Winde JH. Physiological characterization and fed-batch production of an extracellular maltase of Schizosaccharomyces pombe CBS 356. FEMS Yeast Res 2006; 6:888-901. [PMID: 16911511 DOI: 10.1111/j.1567-1364.2006.00091.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
The fission yeast Schizosaccharomyces pombe CBS 356 exhibits extracellular maltase activity. This activity may be of commercial interest as it exhibited a low pH optimum (3.5) and a high affinity for maltose (Km of 7.0+/-1.8 mM). N-terminal sequencing of the protein indicates that it is the product of the AGL1 gene. Regulation of this gene occurs via a derepression/repression mechanism. In sugar- or nitrogen-limited chemostat cultures, the specific rate of enzyme production (q(p)) was independent of the nature of the carbon source (i.e. glucose or maltose), but synthesis was partially repressed by high sugar concentrations. Furthermore, q(p) increased linearly with specific growth rate (mu) between 0.04 and 0.10 h(-1). The enzyme is easily mass-produced in aerobic glucose-limited fed-batch cultures, in which the specific growth rate is controlled to prevent alcoholic fermentation. In fed-batch cultures in which biomass concentrations of 83 g L(-1) were attained, the enzyme concentration reached 58,000 Units per liter culture supernatant. Extracellular maltase may be used as a dough additive in order to prevent mechanisms such as maltose-induced glucose efflux and maltose-hypersensitivity that occur in maltose-consuming Saccharomyces cerevisiae.
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Affiliation(s)
- Mickel L A Jansen
- Kluyver Laboratory of Biotechnology, Delft University of Technology, Delft, The Netherlands
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Hoekema S, Douma RD, Janssen M, Tramper J, Wijffels RH. Controlling light-use byRhodobacter capsulatus continuous cultures in a flat-panel photobioreactor. Biotechnol Bioeng 2006; 95:613-26. [PMID: 16958141 DOI: 10.1002/bit.20907] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The main bottleneck in scale-up of phototrophic fermentation is the low efficiency of light energy conversion to the desired product, which is caused by an excessive dissipation of light energy to heat. The photoheterotrophic formation of hydrogen from acetate and light energy by the microorganism Rhodobacter capsulatus NCIMB 11773 was chosen as a case study in this work. A light energy balance was set up, in which the total bacterial light energy absorption is split up and attributed to its destinations. These are biomass growth and maintenance, generation of hydrogen and photosynthetic heat dissipation. The constants defined in the light energy balance were determined experimentally using a flat-panel photobioreactor with a 3-cm optical path. An experimental method called D-stat was applied. Continuous cultures were kept in a so-called pseudo steady state, while the dilution rate was reduced slowly and smoothly. The biomass yield and maintenance coefficients of Rhodobacter capsulatus biomass on light energy were determined at 12.4 W/m(2) (400-950 nm) and amounted to 2.58 x 10(-8) +/- 0.04 x 10(-8) kg/J and 102 +/- 3.5 W/kg, respectively. The fraction of the absorbed light energy that was dissipated to heat at 473 W/m(2) depended on the biomass concentration in the reactor and varied between 0.80 and 0.88, as the biomass concentration was increased from 2.0 to 8.0 kg/m(3). The process conditions were estimated at which a 3.7% conversion efficiency of absorbed light energy to produced hydrogen energy should be attainable at 473 W/m(2).
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Affiliation(s)
- Sebastiaan Hoekema
- Department of Agro Technology and Food Sciences, Food and Bioprocess Engineering Group, Wageningen University, P.O. Box 8129, 6700 EV Wageningen, The Netherlands.
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Van Der Sluis C, Rahardjo YSP, Smit BA, Kroon PJ, Hartmans S, Ter Schure EG, Tramper J, Wijffels R. Concomitant extracellular accumulation of alpha-keto acids and higher alcohols by Zygosaccharomyces rouxii. J Biosci Bioeng 2005; 93:117-24. [PMID: 16233175 DOI: 10.1016/s1389-1723(02)80002-0] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2001] [Accepted: 08/20/2001] [Indexed: 11/22/2022]
Abstract
Alpha-keto acids are key intermediates in the formation of higher alcohols, important flavor components in soy sauce, and produced by the salt-tolerant yeast Zygosaccharomyces rouxii. Unlike most of the higher alcohols, the alpha-keto acids are usually not extracellularly accumulated by Z. rouxii when it is cultivated with ammonium as the sole nitrogen source. To facilitate extracellular accumulation of the alpha-keto acids from aspartate-derived amino acid metabolism, the amino acids valine, leucine, threonine and methionine were exogenously supplied during batch and A-star cultivations of (routants of) Z. rouxii. It was shown that all alpha-keto acids from the aspartate-derived amino acid metabolism, except alpha-ketobutyrate, could be extracellularly accumulated. In addition, it appeared from the concomitant extracellular accumulation of alpha-keto acids and higher alcohols that in Z. rouxii, valine, leucine and methionine were converted via Ehrlich pathways similar to those in Saccharomyces cerevisiae. Unlike these amino acids, threonine was converted via both the Ehrlich and amino acid biosynthetic pathways in Z. rouxii.
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Affiliation(s)
- Catrinus Van Der Sluis
- Wageningen University, Department of Agrotechnology and Food Sciences, Food and Bioprocess Engineering Group, P.O. Box 8129, 6700 EV Wageningen, The Netherlands.
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Barbosa MJ, Zijffers JW, Nisworo A, Vaes W, van Schoonhoven J, Wijffels RH. Optimization of biomass, vitamins, and carotenoid yield on light energy in a flat-panel reactor using the A-stat technique. Biotechnol Bioeng 2004; 89:233-42. [PMID: 15593095 DOI: 10.1002/bit.20346] [Citation(s) in RCA: 72] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Acceleration-stat (A-stat) cultivations in which the dilution rate is continuously changed at a constant acceleration rate, leading to different average light intensities inside the photobioreactor, can supply more information and reduce experimental time compared with chemostat cultivations. The A-stat was used to optimize the biomass and product yield of continuous cultures of the microalgae D. tertiolecta in a flat-panel reactor. In this study, four different accelerations were studied, a pseudo steady state was maintained at acceleration rates of 0.00016 and 0.00029 h(-2) and results were similar to those of the chemostat. An increase in the acceleration rate led to an increase in the deviation between results obtained in the A-stat and in the chemostats. We concluded that it is advantageous to use the A-stat instead of chemostats to determine culture characteristics and optimize a specific photobioreactor. The effect of average light intensity inside the photobioreactor on the production of vitamins C and E, lutein, and beta-carotene was studied using the A-stat. The highest concentrations of these products were 3.48 +/- 0.46, 0.33 +/- 0.06, 5.65 +/- 0.24, and 2.36 +/- 0.38 mg g(-1), respectively. These results were obtained at different average light intensities, showing the importance of optimizing each product on light intensity.
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Affiliation(s)
- Maria J Barbosa
- Food and Bioprocess Engineering Group, Wageningen University, P.O. Box 8129, 6700 EV Wageningen, The Netherlands.
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Kasemets K, Drews M, Nisamedtinov I, Adamberg K, Paalme T. Modification of A-stat for the characterization of microorganisms. J Microbiol Methods 2003; 55:187-200. [PMID: 14500010 DOI: 10.1016/s0167-7012(03)00143-x] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Two novel modifications of continuous culture with gradual change of dilution rate (A-stat): D-stat and auxo-accelerostat were evaluated in the studies of the effect of changing individual environmental parameters (T, pH, pO(2), substrate concentration, etc.) on growth characteristics of different microorganisms. Common for those cultivation methods is that one environmental parameter is programmed to change with constant change rate (change-stat) while the others are kept constant or in the range not affecting the growth characteristics. The environment response growth curves were obtained starting with chemostat (in A-stat and D-stat) or auxostat (in auxo-accelerostat) steady-state cultures followed by change of set-point value of the desired cultivation parameter. Physiological studies of Saccharomyces sp. and Lactococcus lactis were combined with validation of the different modifications of the A-stat method based on well-known cultivation techniques: chemostat, pH-auxostat, pO(2)-auxostat CO(2)-auxostat and fed-batch. The auxo-accelerostat was shown to be very efficient for cell characterization and dynamic studies in growth environments with excess of essential substrates. Choosing the rate of change of environmental parameters was shown to be critical in comparative physiological studies of microorganisms.
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Affiliation(s)
- Kaja Kasemets
- National Institute of Chemical Physics and Biophysics, Akadeemia tee 23, 12618, Tallinn, Estonia
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Barbosa MJ, Hoogakker J, Wijffels RH. Optimisation of cultivation parameters in photobioreactors for microalgae cultivation using the A-stat technique. BIOMOLECULAR ENGINEERING 2003; 20:115-23. [PMID: 12919788 DOI: 10.1016/s1389-0344(03)00033-9] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Light availability inside the reactor is often the bottleneck in microalgal cultivation and for this reason much attention is being given to light limited growth kinetics of microalgae, aiming at the increase of productivity in photobioreactors. Steady-state culture characteristics are commonly used for productivity optimisation and for cell physiology studies in continuous cultures, and are normally achieved using chemostat cultivations. In the present study, we investigated the applicability of a new and dynamic cultivation method called acceleration-stat (A-stat) to microalgae cultivations where light is the limiting substrate. In the A-stat, the dilution rate is increased at a constant rate. This acceleration rate should be a compromise between a short cultivation time, in order to make it a fast process, and the metabolic adaptation rate of the microorganism to changes in the environment. Simulations of the A-stat were done with different acceleration rates to have an indication of the best rate to use. An A-stat was performed in a pilot plant bubble column (65 l) with Dunaliella tertiolecta as a model organism, and results showed that a pseudo steady state was maintained throughout the experiment. From this work, it was concluded that the A-stat can be used as a fast and accurate tool to determine kinetic parameters and to optimise any specific type of photobioreactor.
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Affiliation(s)
- Maria J Barbosa
- Food and Bioprocess Engineering Group, Wageningen University, P.O. Box 8129, 6700 EV Wageningen, The Netherlands.
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Bibliography. Current awareness on yeast. Yeast 2002; 19:467-74. [PMID: 11921095 DOI: 10.1002/yea.822] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
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