Stability of porcine and microbial lipases to conditions that approximate the small intestine of young birds

In vitro experiments were conducted to study the stability of lipase activities from bacterial, fungal, and animal sources under conditions that approximate the small intestine. In the first experiment, the effects of preincubation with trypsin (500, 1,000, and 2,000 U/mL), chymotrypsin (200, 400, and 800 U/mL), and trypsin plus chymotrypsin (TC; 2,000 U/mL trypsin + 800 U/inL chymotrypsin) for 30 min at 40 C, on lipase activities from sources of Pseudomonas spp. (PL1, PL2), Chromobacterium viscosum (CVL), and Aspergillus niger (ANL) were determined. None of the enzymes were inhibited by trypsin. The chymotrypsin decreased the activity of all of the lipases. The TC had no additional negative effect on the activities of PL1 and PL2; however, ANL and CVL activities were further decreased relative to the chymotrypsin only treatment. In the second study, the effects of Na taurodeoxycholate (0.1 to 16 mM) on the activities of PL1, PL2, CVL, ANL, and crude porcine lipase (CPL) at 23 and 40 C were evaluated. At 23 C, in order of potency, Na taurodeoxycholate inhibited the activities of ANL, CPL, and CVL. At this temperature, Na taurodeoxycholate did not inhibit PL1 and PL2. An increase in the temperature to 40 C increased the activity of all of the enzymes tested. At 40 C, Na taurodeoxycholate had similar effects on lipase activities; however, higher Na taurodeoxycholate levels were required to inhibit ANL activity, and only a partial inhibition of CPL occurred. At 23 C, porcine colipase restored the activity of CPL but had no effect on ANL and CVL in the presence of inhibitory levels of Na taurodeoxycholate. At 40 C, porcine colipase had no effect on Na taurodeoxycholate inhibition of lipase activity. The results of this study indicate that PL is more stable than CVL and ANL, and that colipase addition has no beneficial effects on microbial lipase activities under conditions that approximate the avian small intestine.