title: Physiological regulation and optimization of lipase activity in Pseudomonas aeruginosa EF2.
abstract: Physiological regulation of extracellular lipase activity by a newly-isolated, thermotolerant strain of Pseudomonas aeruginosa (strain EF2) was investigated by growing the organism under various conditions in batch, fed-batch and continuous culture. Lipase activity, measured as the rate of olive oil (predominantly triolein) hydrolysis, was weakly induced by general carbon and/or energy limitation, strongly induced by a wide range of fatty acyl esters including triglycerides, Spans and Tweens, and repressed by long-chain fatty acids including oleic acid. The highest lipase activities were observed during the stationary phase of batch cultures grown on Tween 80, and with Tween 80-limited fed-batch and continuous cultures grown at low specific growth rates. The lipase activity of Tween 80-limited continuous cultures was optimized with respect to pH and temperature using response surface analysis; maximum activity occurred during growth at pH 6.5, 35.5 degrees C, at a dilution rate of 0.04 h-1. Under these conditions the culture exhibited a lipase activity of 39 LU (mg cells)-1 and a specific rate of lipase production (qLipase) of 1.56 LU (mg cells)-1 h-1 (1 LU equalled 1 mumol fatty acid released min-1). Esterase activity, measured with p-nitrophenyl acetate as substrate, varied approximately in parallel with lipase activity under all growth conditions, suggesting that a single enzyme may catalyse both activities.
authors.affiliation: Department of Biochemistry, University of Leicester, UK.
authors.forename: E J
authors.initials: EJ
authors.lastname: Gilbert
authors.forename: J W
authors.initials: JW
authors.lastname: Drozd
authors.forename: C W
authors.initials: CW
authors.lastname: Jones
mesh_terms: D003470:Culture Media; D004950:Esterases / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008049:Lipase / Q000378:metabolism*; D011550:Pseudomonas aeruginosa / Q000201:enzymology* / Q000302:isolation & purification; D013696:Temperature
chemical_list: D003470:Culture Media; D004950:Esterases; D008049:Lipase