Purification and characterization of a novel cholesterol esterase from Pseudomonas aeruginosa,with its application to cleaning lipid-stained contact lenses

With the aim of developing a new cholesterol esterase for eliminating lipids on used contact lenses, microorganisms were screened for the enzyme activity. A Pseudomonas aeruginosa isolated from soil was found to produce a desirable enzyme. The enzyme had an isoelectric point of 3.2, and molecular mass of 58 kDa. The optimal temperature was around 53 degrees C at pH 7.0, and the optimal pH was from 5.5 to 9.5. The enzyme was stable between pH 5 and 10 for 19 h at 25 degrees C, and retained its activity up to 53 degrees C on 30 min of incubation at pH 7.0. The rates of hydrolysis of cholesteryl esters of different fatty acids were in the following order: linoleate > oleate > stearate > palmitate > caprylate > myristate > laurate, caprate > caproate > butyrate, acetate. Addition of (tauro)cholate to a final concentration of 100 mM markedly promoted the hydrolysis of triglycerides of short-, medium-, and long-chain fatty acids. When used with taurocholate, the enzyme acted as an effective cleaner for contact lenses stained with lipids consisting of cholesteryl oleate, tripalmitin, and stearyl stearate.