Controlled Branching by Step-Growth Polymerization of Xylitol and Succinic Acid via Microwave Irradiation.
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ABSTRACT:
SUBMITTER: Mosquera M
PROVIDER: S-EPMC8190812 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:This study explores the relation between biomass-specific succinic acid (SA) production rate and specific growth rate of an engineered industrial strain of Saccharomyces cerevisiae, with the aim to investigate the extent to which growth and product formation can be uncoupled. Ammonium-limited aerobic chemostat and retentostat cultures were grown at different specific growth rates under industrially relevant conditions, that is, at a culture pH of 3 and with sparging of a 1:1 CO2 -air mixture. Biomass-specific SA production rates decreased asymptotically with decreasing growth rate. At near-zero growth rates, the engineered strain maintained a stable biomass-specific SA production rate for over 500 h, with a SA yield on glucose of 0.61 mol mol-1 . These results demonstrate that uncoupling of growth and SA production could indeed be achieved. A linear relation between the biomass-specific SA production rate and glucose consumption rate indicated the coupling of SA production rate and the flux through primary metabolism. The low culture pH resulted in an increased death rate, which was lowest at near-zero growth rates. Nevertheless, a significant amount of non-viable biomass accumulated in the retentostat cultures, thus underlining the importance of improving low-pH tolerance in further strain development for industrial SA production with S. cerevisiae.
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Project description:To understand cell responses against high succinate stress, a continuous culture was performed for 9 months using a wild Escherichia coli under gradually increasing succinate stress. The final adapted strain against high succinate stress, named DST160, was able to grow with no lag phase in medium containing 1.35 M of succinate stress while wild W3110 showed more than 38 h lag phase. The maximum growth rate and growth yield of DST160 under the stress condition were 0.20 h-1 and 0.192 g-cell/g-glucose, which were 53.8 % and 12.3 % higher than those of W3110 (0.13 h-1 and 0.171 g-cell/g-glucose, respectively).
2009-10-30 | GSE17991 | GEO
Project description:To understand cell responses against high succinate stress, a continuous culture was performed for 9 months using a wild Escherichia coli under gradually increasing succinate stress. The final adapted strain against high succinate stress, named DST160, was able to grow with no lag phase in medium containing 1.35 M of succinate stress while wild W3110 showed more than 38 h lag phase. The maximum growth rate and growth yield of DST160 under the stress condition were 0.20 h-1 and 0.192 g-cell/g-glucose, which were 53.8 % and 12.3 % higher than those of W3110 (0.13 h-1 and 0.171 g-cell/g-glucose, respectively). A single colony of E. coli W3110 was inoculated into a 15-mL tube containing 4 mL of LB medium. After 12 h cultivation in a shaking incubator at 37℃ and 220 rpm, pre-culture (1 mL) was transferred to a 250 mL-fermentor (Mini-chemostat fermentor; Biotron Inc., Bucheon, Korea) containing 100 mL medium consisted of M9-glucose minimal medium (3 g glucose , 0.8 g NH4Cl, 0.5 g NaCl, 7.5 g Na2HPO4•2H2O, 3 g KH2PO4 with separately added trace elements of 0.2 g MgSO4•7H2O, 0.1 g CaCl2, 1 mg thiamine) per liter supplemented with 254 mmole of succinate (30 g succinic acid) per liter. The initial pH of the medium was set to be pH 7.5 by adding 6N NaOH. The fermentor was operated at 37℃, 350 rpm with air flushing (100 mL/min.). After 12 h batch mode growth, feeding and outlet pumps were turned on at flow rate of 0.167 mL/min (Dilution rate=0.1 h-1). The fresh medium reservoir (10 L) contained the same contents and pH with the initial medium. Every 10 turnover time (100 h), the reservoir was changed with the same medium composition except succinate concentration. The succinate concentration of the reservoir was gradually increased by 25.4 ~ 84.7 mM (3 ~ 10 g/L of succinic acid) at a time than previous states depending on the cell concentrations at the outlet. When the cell concentration was reduced below O.D.=0.2, succinate feeding pump was temporarily stopped to go back to the slightly lower succinate concentration. The continuous culture was performed until the steady state when succinate in the reservoir reached 1.35 M (160 g/L in succinic acid form). The final adapted cells in 100 mL culture were harvested by centrifuge and frozen rapidly in a liquid nitrogen tank for further analyses including DNA microarray. To understand the change of up/down regulations in the high-succinate adapted E. coli, total mRNAs of control cells and the adapted E. coli cells were extracted using a RNA extraction kit (RNeasy mini kit; Quiagen, Hilden, Germany), and the transcriptomes were compared using DNA microarray. Hybridization and washing were accomplished by a facility of Digital Genomics Co (Seoul, Korea). DNA microarray were scanned using an Axon GenePix 4000B Scanner (Axon Instruments, Union City, CA, USA), and the scanned images were analyzed with GenePix Pro 3.0 software to obtain gene expression ratios.
2009-10-29 | E-GEOD-17991 | biostudies-arrayexpress