title: Improved production of Pseudomonas sp. ECU1011 acetyl esterase by medium design and fed-batch fermentation.
abstract: We optimized culture medium and batch-fed fermentation conditions to enhance production of an acetyl esterase from Pseudomonas sp. ECU1011 (PSAE). This enzyme enantioselectively deacetylates α-acetoxyphenylacetic acid. The medium was redesigned by single-factor and statistical optimization. The addition of ZnSO(4) enhanced enzyme production by 37%. Yeast extract concentration was directly associated with the enzyme production. The fermentation was scaled up in a 5-l fermenter with the optimized medium, and the correlations between enzyme production and dissolved oxygen, pH, and feeding strategy were investigated. The fermentation process was highly oxygen-demanding, pH sensitive and mandelic acid-inducible. The fermentation pH was controlled at 7.5 by a pH and dissolved oxygen feedback strategy. Feeding mandelic acid as both a pH regulator and an enzyme inducer increased the enzyme production by 23%. The results of the medium redesign experiments were confirmed and explained in fed-batch culture experiments. Mathematical models describing the fermentation processes indicated that the enzyme production was strongly associated with cell growth. The optimized pH and dissolved oxygen stat fed-batch process resulted high volumetric production of PSAE (4166 U/l, 7.2-fold higher than the initial) without enantioselectivity decline. This process has potential applications for industrial production of chiral mandelic acid or its derivatives.
authors.affiliation: Laboratory of Biocatalysis and Bioprocessing, State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, 130 Meilong Road, Shanghai, People's Republic of China.
authors.forename: Xin
authors.initials: X
authors.lastname: Ju
authors.forename: Hui-Lei
authors.initials: HL
authors.lastname: Yu
authors.forename: Jiang
authors.initials: J
authors.lastname: Pan
authors.forename: Jian-He
authors.initials: JH
authors.lastname: Xu
mesh_terms: D000115:Acetylesterase / Q000096:biosynthesis*; D001426:Bacterial Proteins / Q000096:biosynthesis*; D019149:Bioreactors; D003470:Culture Media / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D008954:Models, Biological; D010101:Oxygen Consumption / Q000502:physiology; D011549:Pseudomonas / Q000201:enzymology* / Q000254:growth & development*
chemical_list: D001426:Bacterial Proteins; D003470:Culture Media; D000115:Acetylesterase