Tweens and ionic detergents in the hydrolytic activity of Pseudomonas mendocina 3121-1 lipase

Abstract

A more detailed analysis of Pseudomonas mendocina 3121-1 lipase catalytic activity in hydrolysing non-ionic detergents Tweens was the goal of the present study. Tweens as lipase substrates were used in aqueous media at the following final concentrations: half of the critical micelle concentration (CMC), close to CMC, five-fold above CMC and by far exceeding CMC (11–44 mM). The intensity of the hydrolysis of the detergents increased with increasing fatty acid chain length in the Tween structure. The reaction rate also depended on the detergent concentration and changed (increased) at the point when it exceeded the CMC, suggesting that Tweens at those concentrations are not well suitable for stabilizing the Ps. mendocina lipase substrate emulsion. The role of ionic detergents in the lipase-catalysed hydrolysis of soluble substrate p-nitrophenyl butyrate (p-NPB) was also investigated. The hydrolytic activity was shown to be rapidly declined by sodium dodecylsulphate (SDS) during the first 10 min, slower inactivated by dodecyltrimethylammonium bromide (DTMAB) and only slightly affected by sodium deoxycholate (SDCh). The inactivation rate constants (kinact, min–1) were calculated to be 0.29, 0.07 and 0.006 for SDS, DTMAB and SDCh, respectively. Keywords: bacterial lipase, Tweens, ionic detergents, critical micelle concentration, hydrolytic activity