Stability of porcine and microbial lipases to conditions that approximate the proventriculus of young birds.

In vitro experiments were conducted to characterize the activity and the stability of lipase from animal (crude porcine, CPL; lyophilized porcine, LPL), fungal (Rhizopus arrhizus, RAL; Aspergillus niger, ANL), and bacterial (two Pseudomonas spp., PL1, PL2; and Chromobacterium viscosum, CVL) sources when exposed to conditions associated with the glandular stomach. Activity was measured at pH 3 to 8, 40 C and then monitored in response to temperature (40 C), time of exposure (0 and 30 min), pH (3 and 7), and pepsin level (5, 50, and 500 U/mL). All lipases except ANL and CVL had maximum activity at pH 7 to 8. The optimal pH for ANL and CVL were 5 and 6 to 8, respectively. Exposure of lipases to 40 C and pH 7 for 30 min reduced the activity of all lipases except ANL. In contrast, 40 C increased ANL activity 2.5-fold. Although activity of all lipases was reduced by exposure to pH 3, it was nearly eliminated for CPL and LPL. Pepsin concentration had only minor effects on lipase activity and then only at high concentration. The results demonstrate that bacterial lipases (PL1, PL2, and CVL) and ANL are more stable under conditions that approximate the glandular stomach and may explain why dietary porcine lipase has been ineffective in preventing fat malabsorption in previous in vivo studies.