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Batch Fermentation (batch + fermentation)
Selected AbstractsBiosensor online control of citric acid production from glucose by Yarrowia lipolytica using semicontinuous fermentationENGINEERING IN LIFE SCIENCES (ELECTRONIC), Issue 4 2010Lucie Moeller Abstract Our study aimed at the development of an effective method for citric acid production from glucose by use of the yeast Yarrowia lipolytica. The new method included an automated bioprocess control using a glucose biosensor. Several fermentation methodologies including batch, fed-batch, repeated batch and repeated fed-batch cultivation were tested. The best results were achieved during repeated fed-batch cultivation: Within 3 days of cycle duration, approximately 100,g/L citric acid were produced. The yields reached values between 0.51 and 0.65,g/g and the selectivity of the bioprocess for citric acid was as high as 94%. Due to the elongation of the production phase of the bioprocess with growth-decoupled citric acid production, and by operating the fermentation in cycles, an increase in citric acid production of 32% was achieved compared with simple batch fermentation. [source] Supercritical fluid extraction of lipids from the heterotrophic microalga Crypthecodinium cohniiENGINEERING IN LIFE SCIENCES (ELECTRONIC), Issue 2 2010Ricardo Miguel Couto Abstract Microalgae biomass can be a feasible source of ,-3 fatty acids due to its stable and reliable composition. In the present study, the Crypthecodinium cohnii growth and docosahexaenoic acid (DHA, 22:6,3) production in a 100,L glucose-fed batch fermentation was evaluated. The lipid compounds were extracted by supercritical carbon dioxide (SC-CO2) from C. cohnii CCMP 316 biomas, was and their fatty acid composition was analysed. Supercritical fluid extraction runs were performed at temperatures of 313 and 323,K and pressures of 20.0, 25.0 and 30.0,MPa. The optimum extraction conditions were found to be 30.0,MPa and 323,K. Under those conditions, almost 50% of the total oil contained in the raw material was extracted after 3,h and the DHA composition attained 72%,w/w of total fatty acids. The high DHA percentage of total fatty acids obtained by SC-CO2 suggested that this extraction method may be suitable for the production of C. cohnii value added products directed towards pharmaceutical purposes. Furthermore, the fatty acid composition of the remaining lipid fraction from the residual biomass with lower content in polyunsaturated fatty acids could be adequate for further uses as feedstock for biodiesel, contributing to the economy of the overall process suggesting an integrated biorefinery approach. [source] Evaluation of Various Unstructured Kinetic Models for the Production of Protease by Bacillus sphaericus,MTTC511ENGINEERING IN LIFE SCIENCES (ELECTRONIC), Issue 2 2008A. Rajendran Abstract Bacillus sphaericus,MTCC511 was used for the production of protease in submerged batch fermentation. Maximum protease activity of 1010,U/L was obtained during a fermentation period of 24,h under optimized conditions of 30,°C in a medium with an initial pH of 7 and at a shaking rate of 120,rpm. The maximum biomass obtained in the batch fermentation was 2.55,g/L after 16,h. Various unstructured models were analyzed to simulate the experimental values of microbial growth, protease activity and substrate concentration. The unstructured models, i.e. the Monod model for microbial growth, the Monod incorporated Luedeking-Piret model for the production of protease and the Monod-incorporated modified Luedeking-Piret model for the utilization of substrate were capable of predicting the fermentation profile with high coefficient of determination (R2) values of 0.9967, 0.9402 and 0.9729, respectively. The results indicated that the unstructured models were able to describe the fermentation kinetics more effectively. [source] A cost-effective cane molasses medium for enhanced cell-bound phytase production by Pichia anomalaJOURNAL OF APPLIED MICROBIOLOGY, Issue 3 2004A. Vohra Abstract Aim:, Formulation of an inexpensive cane molasses medium for improved cell-bound phytase production by Pichia anomala. Methods and Results:, Cell-bound phytase production by Pichia anomala was compared in synthetic glucose,beef extract and cane molasses media. The yeast was cultivated in 250 ml flasks containing 50 ml of the medium, inoculated with a 12 h-old inoculum (3 × 106 CFU ml,1) and incubated at 25°C for 24 h at 250 rev min,1. Different cultural parameters were optimized in cane molasses medium in batch fermentation. The cell-bound phytase content increased significantly in cane molasses medium (176 U g,1 dry biomass) when compared with the synthetic medium (100 U g,1 dry biomass). In fed-batch fermentation, a marked increase in biomass (20 g l,1) and the phytase yield (3000 U l,1) were recorded in cane molasses medium. The cost of production in cane molasses medium was £0·006 per 1000 U, which is much lower when compared with that in synthetic medium (£0·25 per 1000 U). Conclusions:, An overall 86·6% enhancement in phytase yield was attained in optimized cane molasses medium using fed-batch fermentation when compared with that in synthetic medium. Furthermore, the production in cane molasses medium is cost-effective. Significance and Impact of the Study:, Phytase yield was improved in cane molasses when compared with the synthetic medium, and the cost of production was also significantly reduced. This enzyme can find application in the animal feed industry for improving the nutritional status of feed and combating environmental pollution. [source] Simultaneous saccharification and fermentation of sludge-containing cassava mash for batch and repeated batch production of bioethanol by Saccharomyces cerevisiae CHFY0321JOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 4 2009Gi-Wook Choi Abstract BACKGROUND: The aim of this study was to examine the repeated batch production of bioethanol from sludge-containing cassava mash as starchy substrate by flocculating yeast to improve volumetric bioethanol productivity and to simplify the process of a pre-culture system. RESULTS: For the repeated batch production of bioethanol using cassava mash, the optimal recycling volume ratio was found to be 5%. The repeated batch fermentation was completed within 36 h, while the batch fermentation was completed after 42 h. Volumetric productivity, final ethanol concentration, and ethanol yield were attained to 2.15 g L,1 h,1, 83.64 g L,1, and 85.15%, respectively. Although cell accumulation in the repeated batch process is difficult due to the cassava mash, the repeated batch process using Saccharomyces cerevisiae CHFY0321 could exhibited 10-fold higher initial viable cell number (1.7 × 107 CFU mL,1) than that of the batch process. CONCLUSION: The liquefied cassava powder was directly used for the repeated batch process without removal of sludge. Repeated batch bioethanol production by simultaneous saccharification and fermentation using self-flocculating yeast could reduce process costs and accelerate commercial applications. This result was probably due in part to the effect of the initial viable cell density. Copyright © 2008 Society of Chemical Industry [source] Enhanced production of lovastatin in a bubble column by Aspergillus terreus using a two-stage feeding strategyJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 1 2007EM Rodríguez Porcel Abstract A two-stage feeding strategy is shown to improve the rate of production of lovastatin by Aspergillus terreus when compared with conventional batch fermentation. The feeding strategy consisted of an initial batch/fed-batch phase and a semi-continuous culture dilution phase with retention of pelleted biomass in a slurry bubble column reactor. The batch phase served only to build up the biomass for producing lovastatin, a secondary metabolite that inhibits its own synthesis in the producing microfungus. The semi-continuous dilution phase provided nutrients to sustain the fungus, but prevented biomass growth by limiting the supply of essential nitrogen. (Synthesis of lovastatin does not require nitrogen.) The preferred pelleted growth morphology that favors lovastatin synthesis was readily obtained and maintained in the 20 L bubble column used. In contrast, a stirred tank fermentation had a substantially lower production of lovastatin because mechanical agitation damaged the fungal pellets. The two-stage feeding method increased lovastatin production rate by more than 50% in comparison with the conventional batch operation. Rheological data for the fungal broth are presented. Copyright © 2007 Society of Chemical Industry [source] Clustering multivariate time-series dataJOURNAL OF CHEMOMETRICS, Issue 8 2005Ashish Singhal Abstract A new methodology for clustering multivariate time-series data is proposed. The new methodology is based on calculating the degree of similarity between multivariate time-series datasets using two similarity factors. One similarity factor is based on principal component analysis and the angles between the principal component subspaces while the other is based on the Mahalanobis distance between the datasets. The standard K -means clustering algorithm is modified to cluster multivariate time-series datasets using similarity factors. Simulation data from two nonlinear dynamic systems: a batch fermentation and a continuous exothermic chemical reactor, are clustered to demonstrate the effectiveness of the proposed technique. Comparisons with existing clustering methods show several advantages of the proposed method. Copyright © 2006 John Wiley & Sons, Ltd. [source] Comparison of the performances of different fermentation strategies on cell growth and bacteriocin production by Lactobacillus curvatus CWBI-B28JOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 3 2007Hakim Ghalfi Abstract The dynamics of cell growth and bacteriocin production by Lactobacillus curvatus CWBI-B28 in modified De Man/Rogosa/Sharp (mMRS) broth with various concentrations of glucose and complex nitrogen source (CNS; peptone, yeast extract and meat extract) was investigated in flask fermentations and in a laboratory fermentor using batch and fed-batch cultivations. In fed-batch fermentation the rate of feeding of the reactor with the substrates was either maintained constant (0.12 L h,1) or varied exponentially as a function of time. The results showed that both cell growth and bacteriocin activity were influenced by changes in the concentrations of glucose and CNS. Optimal growth and bacteriocin activity were obtained in mMRS broth containing 40 g L,1 glucose and 40 g L,1 CNS (mMRS40/40). A bacteriocin titre of 4266 AU mL,1 and a cell count of 8.7 log colony-forming units (cfu) mL,1 were recorded when this medium was used for cultivation. In batch fermentation using the same medium, a higher cell count (9.5 log cfu mL,1) and twice as much bacteriocin as in flask fermentation were produced. The highest bacteriocin titre (8533 AU mL,1) was obtained with fed-batch fermentation at an exponentially varying rate of feeding. Bacteriocin activity and cell dry mass did not always correlate. Copyright © 2007 Society of Chemical Industry [source] Sensitivity to Hydrogen Peroxide of Growth and Hyaluronic Acid Production by Streptococcus zooepidemicus ATCC 39920ASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 5-6 2005M.D. Mashitah Abstract The sensitivity to hydrogen peroxide (H2O2) of growth and hyaluronic acid (HA) production by Streptococcus zooepidemicus ATCC 39920 was studied under various conditions. In sheep blood agar-plates, no detectable zone was observed even when the concentration of H2O2 was increased to 0.15 mM. With brain heart infusion-agar and chemically defined medium-agar plates, a profound zone was detected at 0.015 mM concentration of H2O2. To determine the minimal inhibitory concentration (MIC) of the strain in culture broth, various concentrations of H2O2 (0-200 mM) were maintained in the medium prior to fermentation. The result showed that for higher concentrations of H2O2 in the medium, the greater was the inhibition. Streptococcus is catalase-negative and known to produce H2O2 which may affect growth, HA production and glucose utilization. In order to determine at which growth phase H2O2 had the maximum inhibitory activity, a batch fermentation of S. zooepidemicus was conducted in shake flask culture. It was found that H2O2 production took place during the growth phase, and HA production started after the growth had reach late exponential phase when H2O2 in the culture media was depleted. This indicates that H2O2 produced by the cells did not affect cell growth but influenced HA production. [source] Simultaneous saccharification and co-fermentation of paper sludge to ethanol by Saccharomyces cerevisiae RWB222.BIOTECHNOLOGY & BIOENGINEERING, Issue 5 2009Part II: Investigation of discrepancies between predicted, observed performance at high solids concentration Abstract The simultaneous saccharification and co-fermentation (SSCF) kinetic model described in the companion paper can predict batch and fed batch fermentations well at solids concentrations up to 62.4,g/L cellulose paper sludge but not in batch fermentation at 82.0,g/L cellulose paper sludge. Four hypotheses for the discrepancy between observation and model prediction at high solids concentration were examined: ethanol inhibition, enzyme deactivation, inhibition by non-metabolizable compounds present in paper sludge, and mass transfer limitation. The results show that mass transfer limitation was responsible for the discrepancy between model and experimental data. The model can predict the value of high paper sludge SSCF in the fermentation period with no mass transfer limitation. The model predicted that maximum ethanol production of fed-batch fermentation was achieved when it was run as close to batch mode as possible with the initial solids loading below the mass transfer limitation threshold. A method for measuring final enzyme activity at the end of fermentation was also developed in this study. Biotechnol. Bioeng. 2009; 104: 932,938. © 2009 Wiley Periodicals, Inc. [source] Engineering of Pichia pastoris for improved production of antibody fragmentsBIOTECHNOLOGY & BIOENGINEERING, Issue 2 2006Brigitte Gasser Abstract The methylotrophic yeast Pichia pastoris has been used for the expression of many proteins, including antibody fragments. However, limitations became obvious especially when secreting heterodimeric Fab fragments. Up-to-date, antibody fragments have only been expressed under control of the strong inducible alcohol oxidase 1 (AOX1) promoter, which may stress the cells by excessive transcription. Here, we examined the secretion characteristics of single chain and Fab fragments of two different monoclonal anti-HIV1 antibodies (2F5 and 2G12) with both the AOX1 and the glyceraldehyde-3-phosphate dehydrogenase (GAP) promoter. Also, the influences of different secretion leaders and strains were evaluated. Interestingly, secretion was only achieved when using the GAP promoter and the Saccharomyces cerevisiae mating factor , (MF, leader), whereas there was no difference between the two P. pastoris strains. During fed batch fermentation of a 2F5 Fab expressing strain, intracellular retention of Fab heavy chains was observed, while both intact Fab and single light chain molecules were only detected in the supernatants. This led to the conclusion that protein folding and heterodimer assembly in the ER are rate limiting steps in Fab secretion. To alleviate this limitation, S. cerevisiae protein disulfide isomerase (PDI) and the unfolded protein response (UPR) transcription factor HAC1 were constitutively overexpressed in P. pastoris. While the overexpression of HAC1 led to a moderate increase of Fab secretion of 1.3-fold, PDI enabled an increase of the Fab level by 1.9-fold. Hence, the formation of interchain disulfide bonds can be seen as a major rate limiting factor to Fab assembly and subsequent secretion. © 2006 Wiley Periodicals, Inc. [source] Construction and characterization of pta gene-deleted mutant of Clostridium tyrobutyricum for enhanced butyric acid fermentationBIOTECHNOLOGY & BIOENGINEERING, Issue 2 2005Ying Zhu Abstract Clostridium tyrobutyricum ATCC 25755 is an acidogenic bacterium, producing butyrate and acetate as its main fermentation products. In order to decrease acetate and increase butyrate production, integrational mutagenesis was used to disrupt the gene associated with the acetate formation pathway in C. tyrobutyricum. A nonreplicative integrational plasmid containing the phosphotransacetylase gene (pta) fragment cloned from C. tyrobutyricum by using degenerate primers and an erythromycin resistance cassette were constructed and introduced into C. tyrobutyricum by electroporation. Integration of the plasmid into the homologous region on the chromosome inactivated the target pta gene and produced the pta -deleted mutant (PTA-Em), which was confirmed by Southern hybridization. SDS-PAGE and two-dimensional protein electrophoresis results indicated that protein expression was changed in the mutant. Enzyme activity assays using the cell lysate showed that the activities of PTA and acetate kinase (AK) in the mutant were reduced by more than 60% for PTA and 80% for AK. The mutant grew more slowly in batch fermentation with glucose as the substrate but produced 15% more butyrate and 14% less acetate as compared to the wild-type strain. Its butyrate productivity was approximately 2-fold higher than the wild-type strain. Moreover, the mutant showed much higher tolerance to butyrate inhibition, and the final butyrate concentration was improved by 68%. However, inactivation of pta gene did not completely eliminate acetate production in the fermentation, suggesting the existence of other enzymes (or pathways) also leading to acetate formation. This is the first-reported genetic engineering study demonstrating the feasibility of using a gene-inactivation technique to manipulate the acetic acid formation pathway in C. tyrobutyricum in order to improve butyric acid production from glucose. © 2005 Wiley Periodicals, Inc. [source] Data reconciliation of concentration estimates from mid-infrared and dielectric spectral measurements for improved on-line monitoring of bioprocessesBIOTECHNOLOGY PROGRESS, Issue 2 2009Michal Dabros Abstract Real-time data reconciliation of concentration estimates of process analytes and biomass in microbial fermentations is investigated. A Fourier-transform mid-infrared spectrometer predicting the concentrations of process metabolites is used in parallel with a dielectric spectrometer predicting the biomass concentration during a batch fermentation of the yeast Saccharomyces cerevisiae. Calibration models developed off-line for both spectrometers suffer from poor predictive capability due to instrumental and process drifts unseen during calibration. To address this problem, the predicted metabolite and biomass concentrations, along with off-gas analysis and base addition measurements, are reconciled in real-time based on the closure of mass and elemental balances. A statistical test is used to confirm the integrity of the balances, and a non-negativity constraint is used to guide the data reconciliation algorithm toward positive concentrations. It is verified experimentally that the proposed approach reduces the standard error of prediction without the need for additional off-line analysis. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2009 [source] Bioreactor Coupled with Electromagnetic Field Generator: Effects of Extremely Low Frequency Electromagnetic Fields on Ethanol Production by SaccharomycescerevisiaeBIOTECHNOLOGY PROGRESS, Issue 5 2007Victor H. Perez The effect of extremely low frequency (ELF) magnetic fields on ethanol production by Saccharomyces cerevisiae using sugar cane molasses was studied during batch fermentation. The cellular suspension from the fermentor was externally recycled through a stainless steel tube inserted in two magnetic field generators, and consequently, the ethanol production was intensified. Two magnetic field generators were coupled to the bioreactor, which were operated conveniently in simple or combined ways. Therefore, the recycle velocity and intensity of the magnetic field varied in a range of 0.6,1.4 m s,1 and 5,20 mT, respectively. However, under the best conditions with the magnetic field treatment (0.9,1.2 m s,1 and 20 mT plus solenoid), the overall volumetric ethanol productivity was approximately 17% higher than in the control experiment. These results made it possible to verify the effectiveness of the dynamic magnetic treatment since the fermentations with magnetic treatment reached their final stage in less time, i.e., approximately 2 h earlier, when compared with the control experiment. [source] Enhancement of Monascus Pigment Production by the Culture of Monascus sp.BIOTECHNOLOGY PROGRESS, Issue 1 2006J101 at Low Temperature In general, high broth viscosity is a key factor to be considered in a submerged fermentation of filamentous fungi. High broth viscosity was also observed in a batch fermentation of Monascus sp. J101 at 30 °C. In a batch culture at 30 °C, most cell growth was accomplished within 48 h, which induced highly entangled clumps. The resultant high viscosity induced heterogeneity inside the fermentor, poor oxygen transfer, and low pigment yield. However, these problems could be overcome by reducing fungal growth rate through culture at low temperature (25 °C). Cell growth was moderate and continued for 120 h, and low viscosity was maintained. The DO levels remained at 50% or higher with good mixing. As a result, the pigment yield at 25 °C was 10 times greater than at 30 °C. [source] Combined Effect of Agitation/Aeration and Fed-Batch Strategy on Ubiquin- one-10 Production by Pseudomonas diminutaCHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 6 2010Mahesh V. Bule Abstract The effects of aeration rate and agitation speed on ubiquinone-10 (CoQ10) submerged fermentation in a stirred-tank reactor using Pseudomonas diminuta NCIM 2865 were investigated. CoQ10 production, biomass formation, glycerol utilization, and volumetric mass transfer coefficient (kLa) were affected by both aeration and agitation. An agitation speed of 400,rpm and aeration rate of 0.5,vvm supported the maximum production (38.56,mg,L,1) of CoQ10 during batch fermentation. The fermentation run supporting maximum production had an kLa of 27.07,h,1 with the highest specific productivity and CoQ10 yield of 0.064,mg,g,1h,1 and 0.96,mg,g,1 glycerol, respectively. Fermentation kinetics performed under optimum aeration and agitation showed the growth-associated constant (a,=,5.067,mg,g,1) to be higher than the nongrowth-associated constant (,,=,0.0242,mg,g,1h,1). These results were successfully utilized for the development of fed-batch fermentation, which increased the CoQ10 production from 38.56,mg,L,1 to 42.85,mg,L,1. [source] Kinetik des anaeroben Glycerinabbaus mithilfe sulfatreduzierender Bakterien,.CHEMIE-INGENIEUR-TECHNIK (CIT), Issue 10 2010Kinetics of Anaerobic Biodegradation of Glycerol by Sulfate-Reducing Bacteria Anaerobic glycerol degradation; Anaerobic wastewater treatment; biological sulfate reduction; heavy metals and sulphate removal; industrial sewage; Sulphate-reducing bacteria Abstract Die Wirtschaftlichkeit der Produktion von Biosulfid für die Schwermetall- oder Sulfatelimination aus Industrieabwässern hängt ausschlaggebend vom verwendeten Substrat ab und steht in direktem Zusammenhang mit der Verwertbarkeit der Kohlenstoffquelle durch Mikroorganismen. Leicht zugänglich und einfach in der Handhabung ist Glycerin als Substrat für die sulfatreduzierenden Bakterien (SRB). Gegenstand der hier vorgestellten Arbeiten war die Untersuchung des anaeroben Glycerinabbaus in der Batch-Fermentation mithilfe einer Mischkultur von SRB und die Ermittlung eines kinetischen Modellansatzes. The efficiency of the production of Biosulfid for the elimination of heavy metals or sulphate from industrial wastewater is crucial on the used substrate and is directly related to the recoverability of the carbon source by microorganisms. Easily accessible and easy to use is glycerol as substrate for the sulfate-reducing bacteria (SRB). Subject of the presented work was the investigation of the anaerobic degradation of glycerol in the batch fermentation. A mixed culture of SRB and a kinetic model approach was determined. [source] Modelling the growth of Weissella cibaria as a function of fermentation conditionsJOURNAL OF APPLIED MICROBIOLOGY, Issue 5 2009A. Ricciardi Abstract Aims:, To investigate the effect of pH, water activity (aw) and temperature on the growth of Weissella cibaria DBPZ1006, a lactic acid bacterium isolated from sourdoughs. Methods and Results:, The kinetics of growth of W. cibaria DBPZ1006 was investigated during batch fermentations as a function of pH (4·0,8·0), aw (0·935,0·994) and temperature (10,45°C) in a rich medium. The growth curve parameters (lag time, growth rate and asymptote) were estimated using the dynamic model of Baranyi and Roberts (1994. A dynamic approach to predicting bacterial growth in food. Int J Food Microbiol23, 277,294). The effect of pH, aw and temperature on maximum specific growth rate (,max) were estimated by fitting a cardinal model. ,max under optimal conditions (pH = 6·6, aw = 0·994, T = 36·3°C) was estimated to be 0·93 h,1. Minimum and maximum estimated pH and temperature for growth were 3·6 and 8·15, and 9·0°C and 47·8°C, respectively, while minimum aw was 0·918 (equivalent to 12·2% w/v NaCl). Conclusions:,Weissella cibaria DBPZ1006 is a fast-growing heterofermentative strain, which could be used in a mixed starter culture for making bread. Significance and Impact of the Study:, This is the first study reporting the modelling of the growth of W. cibaria, a species that is increasingly being used as a starter in sourdough and vegetable fermentations. [source] Gluconic acid production by Aspergillus terreusLETTERS IN APPLIED MICROBIOLOGY, Issue 3 2010C. Dowdells Abstract Aim:,Aspergillus terreus produces itaconic acid at low pH but lovastatin and other secondary metabolites at higher pH in the fermentation. The utilization of glucose as a carbon substrate was investigated for secondary metabolite production by A. terreus. Methods and Results:, With a starting pH of 6·5, glucose was rapidly metabolized to gluconic acid by the wild-type strain and by transformants harbouring Aspergillus niger genes encoding 6-phosphofructo-1-kinases with superior kinetic and regulatory properties for bioproduction of metabolites from glucose. On exhaustion of the glucose in batch fermentations, the accumulated gluconic acid was utilized as a carbon source. Conclusions:, A novel pathway of glucose catabolism was demonstrated in A. terreus, a species whose wild type is, without any strain development, capable of producing gluconic acid at high molar conversion efficiency (up to 0·7 mol mol,1 glucose consumed). Significance and Impact of the Study:,Aspergillus terreus is a potential novel producer organism for gluconic acid, a compound with many uses as a bulk chemical. With a new knowledge of glucose catabolism by A. terreus, fermentation strategies for secondary metabolite production can be devised with glucose feeding using feedback regulation by pH. [source] Simultaneous saccharification and co-fermentation of paper sludge to ethanol by Saccharomyces cerevisiae RWB222.BIOTECHNOLOGY & BIOENGINEERING, Issue 5 2009Part II: Investigation of discrepancies between predicted, observed performance at high solids concentration Abstract The simultaneous saccharification and co-fermentation (SSCF) kinetic model described in the companion paper can predict batch and fed batch fermentations well at solids concentrations up to 62.4,g/L cellulose paper sludge but not in batch fermentation at 82.0,g/L cellulose paper sludge. Four hypotheses for the discrepancy between observation and model prediction at high solids concentration were examined: ethanol inhibition, enzyme deactivation, inhibition by non-metabolizable compounds present in paper sludge, and mass transfer limitation. The results show that mass transfer limitation was responsible for the discrepancy between model and experimental data. The model can predict the value of high paper sludge SSCF in the fermentation period with no mass transfer limitation. The model predicted that maximum ethanol production of fed-batch fermentation was achieved when it was run as close to batch mode as possible with the initial solids loading below the mass transfer limitation threshold. A method for measuring final enzyme activity at the end of fermentation was also developed in this study. Biotechnol. Bioeng. 2009; 104: 932,938. © 2009 Wiley Periodicals, Inc. [source] Fermentative production of l -glycerol 3-phosphate utilizing a Saccharomyces cerevisiae strain with an engineered glycerol biosynthetic pathway,BIOTECHNOLOGY & BIOENGINEERING, Issue 3 2008A. Popp Abstract Interest in l -glycerol 3-phosphate (l -G3P) production via microbial fermentation is due to the compound's potential to replace the unstable substrate dihydroxyacetone phosphate (DHAP) in one-pot enzymatic carbohydrate syntheses. A Saccharomyces cerevisiae strain with deletions in both genes encoding specific l -G3Pases (GPP1 and GPP2) and multicopy overexpression of l -glycerol 3-phosphate dehydrogenase (GPD1) was studied via small-scale (100 mL) batch fermentations under quasi-anaerobic conditions. Intracellular accumulation of l -G3P reached extremely high levels (roughly 200 mM) but thereafter declined. Extracellular l -G3P was also detected and its concentration continuously increased throughout the fermentation, such that most of the total l -G3P was found outside the cells as fermentation concluded. Moreover, in spite of the complete elimination of specific l -G3Pase activity, the strain showed considerable glycerol formation suggesting unspecific dephosphorylation as a mechanism to relieve cells of intracellular l -G3P accumulation. Up-scaling the process employed fed-batch fermentation with repeated glucose feeding, plus an aerobic growth phase followed by an anaerobic product accumulation phase. This produced a final product titer of about 325 mg total l -G3P per liter of fermentation broth. Biotechnol. Bioeng. 2008;100: 497,505. © 2008 Wiley Periodicals, Inc. [source] Growth of Rhodospirillum rubrum on synthesis gas: Conversion of CO to H2 and poly-,-hydroxyalkanoateBIOTECHNOLOGY & BIOENGINEERING, Issue 2 2007Young S. Do Abstract To examine the potential use of synthesis gas as a carbon and energy source in fermentation processes, Rhodospirillum rubrum was cultured on synthesis gas generated from discarded seed corn. The growth rates, growth and poly-,-hydroxyalkanoates (PHA) yields, and CO oxidation/H2 evolution rates were evaluated in comparison to the rates observed with an artificial synthesis gas mixture. Depending on the gas conditioning system used, synthesis gas either stimulated or inhibited CO-oxidation rates compared to the observations with the artificial synthesis gas mixture. Inhibitory and stimulatory compounds in synthesis gas could be removed by the addition of activated charcoal, char-tar, or char-ash filters (char, tar, and ash are gasification residues). In batch fermentations, approximately 1.4 mol CO was oxidized per day per g cell protein with the production of 0.75 mol H2 and 340 mg PHA per day per g cell protein. The PHA produced from R. rubrum grown on synthesis gas was composed of 86% ,-hydroxybutyrate and 14% ,-hydroxyvalerate. Mass transfer of CO into the liquid phase was determined as the rate-limiting step in the fermentation. Biotechnol. Bioeng. 2007;97: 279,286. © 2006 Wiley Periodicals, Inc. [source] Increased recombinant protein production in Escherichia coli strains with overexpressed water-forming NADH oxidase and a deleted ArcA regulatory proteinBIOTECHNOLOGY & BIOENGINEERING, Issue 3 2006G.N. Vemuri Glycolytic flux is increased and acetate production is reduced in Escherichia coli by the expression of heterologous NADH oxidase (NOX) from Streptococcus pneumoniae coupled with the deletion of the arcA gene, which encodes the ArcA regulatory protein. In this study, we examined the overproduction of a model recombinant protein in strains of E. coli expressing NOX with or without an arcA mutation. The presence of NOX or the absence of ArcA reduced acetate by about 50% and increased ,-galactosidase production by 10,20%. The presence of NOX in the arcA strain eliminated acetate production entirely in batch fermentations and resulted in a 120% increase in ,-galactosidase production. © 2006 Wiley Periodicals, Inc. [source] Assessment of physiological conditions in E. coli fermentations by epifluorescent microscopy and image analysisBIOTECHNOLOGY PROGRESS, Issue 3 2009Sónia Carneiro Abstract The development of monitoring methods for assessing the physiological state of microorganisms during recombinant fermentation processes has been encouraged by the need to evaluate the influence of processing conditions in recombinant protein production. In this work, a technique based on microscopy and image analysis was developed that allows the simultaneous quantification of parameters associated with viability and fluorescent protein production in recombinant Escherichia coli fermentations. Images obtained from light microscopy with phase contrast are used to assess the total number of cells in a given sample and, from epifluorescence microscopy, both protein producing and injured cells are evaluated using two different fluorochromes: propidium iodide and enhanced yellow fluorescent protein. This technique revealed the existence of different cell populations in the recombinant E. coli fermentation broth that were evaluated along four batch fermentations, complementing information obtained with standard techniques to study the effects of the temperature and induction time in recombinant protein production processes. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2009 [source] Comparison of glucose/xylose cofermentation of poplar hydrolysates processed by different pretreatment technologiesBIOTECHNOLOGY PROGRESS, Issue 2 2009Yulin Lu Abstract The inhibitory effects of furfural and acetic acid on the fermentation of xylose and glucose to ethanol in YEPDX medium by a recombinant Saccharomyces cerevisiae strain (LNH-ST 424A) were investigated. Initial furfural concentrations below 5 g/L caused negligible inhibition to glucose and xylose consumption rates in batch fermentations with high inoculum (4.5,6.0 g/L). At higher initial furfural concentrations (10,15 g/L) the inhibition became significant with xylose consumption rates especially affected. Interactive inhibition between acetic acid and pH were observed and quantified, and the results suggested the importance of conditioning the pH of hydrolysates for optimal fermentation performance. Poplar biomass pretreated by various CAFI processes (dilute acid, AFEX, ARP, SO2 -catalyzed steam explosion, and controlled-pH) under respective optimal conditions was enzymatically hydrolyzed, and the mixed sugar streams in the hydrolysates were fermented. The 5-hydroxymethyl furfural (HMF) and furfural concentrations were low in all hydrolysates and did not pose negative effects on fermentation. Maximum ethanol productivity showed that 0,6.2 g/L initial acetic acid does not substantially affect the ethanol fermentation with proper pH adjustment, confirming the results from rich media fermentations with reagent grade sugars. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2009 [source] Effect of Different Carbon Sources on the Production of Succinic Acid Using Metabolically Engineered Escherichia coliBIOTECHNOLOGY PROGRESS, Issue 2 2007Christian Andersson Succinic acid (SA) is an important platform molecule in the synthesis of a number of commodity and specialty chemicals. In the present work, dual-phase batch fermentations with the E. coli strain AFP184 were performed using a medium suited for large-scale industrial production of SA. The ability of the strain to ferment different sugars was investigated. The sugars studied were sucrose, glucose, fructose, xylose, and equal mixtures of glucose and fructose and glucose and xylose at a total initial sugar concentration of 100 g L,1. AFP184 was able to utilize all sugars and sugar combinations except sucrose for biomass generation and succinate production. For sucrose as a substrate no succinic acid was produced and none of the sucrose was metabolized. The succinic acid yield from glucose (0.83 g succinic acid per gram glucose consumed anaerobically) was higher than the yield from fructose (0.66 g g,1). When using xylose as a carbon source, a yield of 0.50 g g,1 was obtained. In the mixed-sugar fermentations no catabolite repression was detected. Mixtures of glucose and xylose resulted in higher yields (0.60 g g,1) than use of xylose alone. Fermenting glucose mixed with fructose gave a lower yield (0.58 g g,1) than fructose used as the sole carbon source. The reason is an increased pyruvate production. The pyruvate concentration decreased later in the fermentation. Final succinic acid concentrations were in the range of 25,40 g L,1. Acetic and pyruvic acid were the only other products detected and accumulated to concentrations of 2.7,6.7 and 0,2.7 g L,1. Production of succinic acid decreased when organic acid concentrations reached approximately 30 g L,1. This study demonstrates that E. coli strain AFP184 is able to produce succinic acid in a low cost medium from a variety of sugars with only small amounts of byproducts formed. [source] Optimization of Cyclodextrin Glycosyltransferase Production from KlebsiellapneumoniaeAS-22 in Batch, Fed-Batch, and Continuous CulturesBIOTECHNOLOGY PROGRESS, Issue 6 2003Bharat N. Gawande Production of a novel cyclodextrin glycosyltransferase (CGTase) from Klebsiella pneumoniaeAS-22 strain, which converts starch predominantly to ,-CD at high conversion yields, in batch, fed-batch, and continuous cultures, is presented. In batch fermentations, optimization of different operating parameters such as temperature, pH, agitation speed, and carbon-source concentration resulted in more than 6-fold increase in CGTase activity. The enzyme production was further improved by two fed-batch approaches. First, using glucose-based feed to increase cell density, followed by starch-based feed to induce enzyme production, resulted in high cell density of 76 g dry cell weight/L, although the CGTase production was low. Using the second approach of a single dextrin-based feed, 20-fold higher CGTase was produced compared to that in batch fermentations with media containing tapioca starch. In continuous operation, more than 8-fold increase in volumetric CGTase productivity was obtained using dextrin-based media compared to that in batch culture using starch-based media. [source] | |||||||||||||||||||||||||