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Fed-batch Experiments (fed-batch + experiment)
Selected AbstractsFed-Batch Cultivation of Saccharomyces cerevisiae in a Hyperbaric BioreactorBIOTECHNOLOGY PROGRESS, Issue 2 2003I. Belo Fed-batch is the dominating mode of operation in high-cell-density cultures of Saccharomyces cerevisaein processes such as the production of bakerapos;s yeast and recombinant proteins, where the high oxygen demand of these cultures makes its supply an important and difficult task. The aim of this work was to study the use of hyperbaric air for oxygen mass transfer improvement on S. cerevisiaefed-batch cultivation. The effects of increased air pressure up to 1.5 MPa on cell behavior were investigated. The effects of oxygen and carbon dioxide were dissociated from the effects of total pressure by the use of pure oxygen and gas mixtures enriched with CO2. Fed-batch experiments were performed in a stirred tank reactor with a 600 mL stainless steel vessel. An exponential feeding profile at dilution rates up to 0.1 h,1 was used in order to ensure a subcritical flux of substrate and, consequently, to prevent ethanol formation due to glucose excess. The ethanol production observed at atmospheric pressure was reduced by the bioreactor pressurization up to 1.0 MPa. The maximum biomass yield, 0.5 g g,1 (cell mass produced per mass of glucose consumed) was attained whenever pressure was increased gradually through time. This demonstrates the adaptive behavior of the cells to the hyperbaric conditions. This work proved that hyperbaric air up to 1.0 MPa (0.2 MPa of oxygen partial pressure) could be applied to S. cerevisiaecultivation under low glucose flux. Above that critical oxygen partial pressure value, i.e., for oxygen pressures of 0.32 and 0.5 MPa, a drastic cell growth inhibition and viability loss were observed. The increase of carbon dioxide partial pressure in the gas mixture up to 48 kPa slightly decreased the overall cell mass yield but had negligible effects on cell viability. [source] D -Lactic acid production from waste cardboardJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 1 2005Remedios Yáñez Abstract The effects caused by alkaline treatment on the susceptibility of waste cardboard to enzymatic hydrolysis have been studied. Optimised conditions leading to extensive saccharification of both cellulose (870 g kg,1 conversion) and hemicelluloses (845 g kg,1 conversion) were identified. Samples treated under selected operational conditions were employed for producing D -lactic acid by simultaneous saccharification and fermentation (SSF) in media containing cellulases, ,-glucosidase and Lactobacillus coryniformis ssp torquens cells. SSF fed-batch experiments led to D -lactic acid concentrations up to 23.4 g dm,3 at a product yield of 514 g lactic acid kg,1 of potential glucose and a volumetric productivity of 0.48 g dm,3 h,1. Copyright © 2004 Society of Chemical Industry [source] Quantitative physiology of Pichia pastoris during glucose-limited high-cell density fed-batch cultivation for recombinant protein productionBIOTECHNOLOGY & BIOENGINEERING, Issue 2 2010Jan Heyland Abstract Pichia pastoris has become one of the major microorganisms for the production of proteins in recent years. This development was mainly driven by the readily available genetic tools and the ease of high-cell density cultivations using methanol (or methanol/glycerol mixtures) as inducer and carbon source. To overcome the observed limitations of methanol use such as high heat development, cell lysis, and explosion hazard, we here revisited the possibility to produce proteins with P. pastoris using glucose as sole carbon source. Using a recombinant P. pastoris strain in glucose limited fed-batch cultivations, very high-cell densities were reached (more than 200,gCDW,L,1) resulting in a recombinant protein titer of about 6.5,g,L,1. To investigate the impact of recombinant protein production and high-cell density fermentation on the metabolism of P. pastoris, we used 13C-tracer-based metabolic flux analysis in batch and fed-batch experiments. At a controlled growth rate of 0.12,h,1 in fed-batch experiments an increased TCA cycle flux of 1.1,mmol,g,1,h,1 compared to 0.7,mmol,g,1,h,1 for the recombinant and reference strains, respectively, suggest a limited but significant flux rerouting of carbon and energy resources. This change in flux is most likely causal to protein synthesis. In summary, the results highlight the potential of glucose as carbon and energy source, enabling high biomass concentrations and protein titers. The insights into the operation of metabolism during recombinant protein production might guide strain design and fermentation development. Biotechnol. Bioeng. 2010;107: 357,368. © 2010 Wiley Periodicals, Inc. [source] Dynamic gene expression regulation model for growth and penicillin production in Penicillium chrysogenumBIOTECHNOLOGY & BIOENGINEERING, Issue 4 2010Rutger D. Douma Abstract As is often the case for microbial product formation, the penicillin production rate of Penicillium chrysogenum has been observed to be a function of the growth rate of the organism. The relation between the biomass specific rate of penicillin formation (qp) and growth rate (µ) has been measured under steady state conditions in carbon limited chemostats resulting in a steady state qp(µ) relation. Direct application of such a relation to predict the rate of product formation during dynamic conditions, as they occur, for example, in fed-batch experiments, leads to errors in the prediction, because qp is not an instantaneous function of the growth rate but rather lags behind because of adaptational and regulatory processes. In this paper a dynamic gene regulation model is presented, in which the specific rate of penicillin production is assumed to be a linear function of the amount of a rate-limiting enzyme in the penicillin production pathway. Enzyme activity assays were performed and strongly indicated that isopenicillin-N synthase (IPNS) was the main rate-limiting enzyme for penicillin-G biosynthesis in our strain. The developed gene regulation model predicts the expression of this rate limiting enzyme based on glucose repression, fast decay of the mRNA encoding for the enzyme as well as the decay of the enzyme itself. The gene regulation model was combined with a stoichiometric model and appeared to accurately describe the biomass and penicillin concentrations for both chemostat steady-state as well as the dynamics during chemostat start-up and fed-batch cultivation. Biotechnol. Bioeng. 2010;106: 608,618. © 2010 Wiley Periodicals, Inc. [source] Logistic Equations Effectively Model Mammalian Cell Batch and Fed-Batch Kinetics by Logically Constraining the FitBIOTECHNOLOGY PROGRESS, Issue 4 2005Chetan T. Goudar A four-parameter logistic equation was used to fit batch and fed-batch time profiles of viable cell density in order to estimate net growth rates from the inoculation through the cell death phase. Reduced three-parameter forms were used for nutrient uptake and metabolite/product formation rate calculations. These logistic equations constrained the fits to expected general concentration trends, either increasing followed by decreasing (four-parameter) or monotonic (three-parameter). The applicability of this approach was first verified for Chinese hamster ovary (CHO) cells cultivated in 15-L batch bioreactors. Cell density, metabolite, and nutrient concentrations were monitored over time and used to estimate the logistic parameters by nonlinear least squares. The logistic models fit the experimental data well, supporting the validity of this approach. Further evidence to this effect was obtained by applying the technique to three previously published batch studies for baby hamster kidney (BHK) and hybridoma cells in bioreactors ranging from 100 mL to 300 L. In 27 of the 30 batch data sets examined, the logistic models provided a statistically superior description of the experimental data than polynomial fitting. Two fed-batch experiments with hybridoma and CHO cells in benchtop bioreactors were also examined, and the logistic fits provided good representations of the experimental data in all 25 data sets. From a computational standpoint, this approach was simpler than classical approaches involving Monod-type kinetics. Since the logistic equations were analytically differentiable, specific rates could be readily estimated. Overall, the advantages of the logistic modeling approach should make it an attractive option for effectively estimating specific rates from batch and fed-batch cultures. [source] | ||||||||||