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Physiological regulation and optimization of lipase activity in Pseudomonas aeruginosa EF2
Abstract
Summary: 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 †C, at a dilution rate of 0·04 h−1. Under these conditions the culture exhibited a lipase activity of 39 LU (mg cells)−1and a specific rate of lipase production (q Lipase) of 1·56 LU (mg cells)−1h−1(1 LU equalled 1 μmol 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.
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© Society for General Microbiology 1991