title: Effect of process parameters on succinic acid production in Escherichia coli W3110 and enzymes involved in the reductive tricarboxylic acid cycle.
abstract: The effect of process optimization on succinic acid production by Escherichia coli W3110 and on enzymes involved in the reverse tricarboxylic acid cycle was studied. Approximately, 7.02 g L-1 of succinic acid was produced in 60 h at pH 7.0 in 500 mL anaerobic bottles containing 300 mL of the medium, wherein the sucrose concentration was 2.5%, the ratio of tryptone to ammonium hydrogen phosphate was 1:1, and the concentration of magnesium carbon ate was 1.5%. When these optimized fermentation conditions were employed in a 10 L bioreactor, 11.2 g L-1 of succinic acid was produced in 48 h. This is a 10-fold increase in succinic acid production from the initial titer of 0.94 g L-1. This clearly indicates the importance of process optimization, where by manipulating the media composition and production conditions, a remarkable increase in the production of the desired biomolecule can be obtained. The production of succinic acid is a multi-step reaction through the reverse tricarboxylic acid cycle. A linear relationship was observed between succinic acid production and the enzyme activities. The enzyme activities were found to increase in the order phospho-enol-pyruvate carboxylase<malate dehydrogenase<fumarase<fumarate reductase. The activity of phospho-enol-pyruvate carboxykinase was also estimated. Results indicate that this enzyme was not a very active participant in the production of succinic acid, since it catalyzes the phosphorylation of oxaloacetic acid to yield phospho-enol-pyruvate.
authors.affiliation: Department of Microbiology, University of Delhi South Campus, New Delhi, India.
authors.forename: Jasmine
authors.initials: J
authors.lastname: Isar
authors.forename: Lata
authors.initials: L
authors.lastname: Agarwal
authors.forename: Saurabh
authors.initials: S
authors.lastname: Saran
authors.forename: Pritesh
authors.initials: P
authors.lastname: Gupta
authors.forename: Rajendra Kumar
authors.initials: RK
authors.lastname: Saxena
mesh_terms: D000693:Anaerobiosis; D019149:Bioreactors / Q000382:microbiology; D002952:Citric Acid Cycle; D004926:Escherichia coli / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D005285:Fermentation; D006863:Hydrogen-Ion Concentration; D007218:Industrial Microbiology / Q000379:methods; D007477:Ions / Q000378:metabolism / Q000494:pharmacology; D008274:Magnesium / Q000378:metabolism / Q000494:pharmacology; D010461:Peptones / Q000378:metabolism / Q000494:pharmacology; D010710:Phosphates / Q000378:metabolism / Q000494:pharmacology; D010730:Phosphoenolpyruvate Carboxylase / Q000378:metabolism; D019802:Succinic Acid / Q000378:metabolism*; D013395:Sucrose / Q000378:metabolism / Q000494:pharmacology; D013696:Temperature
chemical_list: D007477:Ions; D010461:Peptones; D010710:Phosphates; C024788:ammonium phosphate; C005479:magnesium carbonate; D013395:Sucrose; C001830:tryptones; D019802:Succinic Acid; D010730:Phosphoenolpyruvate Carboxylase; D008274:Magnesium