title: Immobilized cells of recombinant Escherichia coli strain for continuous production of L-aspartic acid.
abstract: For L-aspartic acid biosynthesis, high production cells of Escherichia coli mutant B-715 and P1 were immobilized in chitosan gel using a technique developed in our laboratory. The immobilization process reduced initial activity of the intact cells, however, the biocatalyst produced was very stabile for long-term use in multi-repeated batch or continuous processes. Temperature influence on the conversion of ammonium fumarate to L-aspartic acid was investigated. In long-term experiments, over 603 hours, the temperature 40 degrees C was found to be the best for both biocatalyst stability and high conversion rate. The optimum substrate concentration was 1.0 M. Continuous production of L-aspartic acid was investigated in three types of column bioreactors characterized by different volumes as well as different high to biocatalyst bed volume rations (Hz/Vz). The highest conversion rate, 99.8%, and the productivity 6 g/g/h (mass of L-aspartic acid per dry mass of cells in biocatalyst per time unit) was achieved in the bioreactor with the highest value Hz/Vz = 3.1, and liquid hour space velocity value of 5.2, defined as the volume of feeding substrate passed per volume of catalyst in bioreactor per one hour.
authors: Department of Biosynthesis of Drugs, Chair of Biology and Pharmaceutical Biotechnology, Medical University of Łódź, Poland. grazyna.szymanska@umed.lodz.pl
authors: Grazyna
authors: G
authors: Szymańska
authors: Bogusław
authors: B
authors: Sobierajski
authors: Aleksander
authors: A
authors: Chmiel
mesh_terms: D001224:Aspartic Acid / Q000096:biosynthesis*; D055162:Biocatalysis; D019149:Bioreactors / Q000382:microbiology*; D018914:Cells, Immobilized / Q000378:metabolism; D048271:Chitosan / Q000737:chemistry; D003470:Culture Media / Q000737:chemistry; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism*; D005650:Fumarates / Q000378:metabolism*; D009154:Mutation; D013696:Temperature; D013997:Time Factors
chemical_list: D003470:Culture Media; D005650:Fumarates; D001224:Aspartic Acid; C032005:fumaric acid; D048271:Chitosan