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 t he stability of lipase from animal (crude porcine, CPL; lyophilized po rcine, LPL), fungal (Rhizopus arrhizus, RAL; Aspergillus niger, ANL), and bacterial (two Pseudomonas spp., PL1, PL2; and Chromobacterium vis cosum, CVL) sources when exposed to conditions associated with the gla ndular stomach. Activity was measured at pH 3 to 8, 40 C and then moni tored in response to temperature (40 C), time of exposure (0 and 30 mi n), 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 f or 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 A NL. Ln contrast, 40 C increased ANL activity 2.5-fold. Although activi ty of all lipases was reduced by exposure to pH 3, it was nearly elimi nated for CPL and LPL. Pepsin concentration had only minor effects on lipase activity and then only at high concentration. The results demon strate that bacterial lipases (PL1, PL2, and CVL) and ANL are more sta ble under conditions that approximate the glandular stomach and may ex plain why dietary porcine lipase has been ineffective in preventing fa t malabsorption in previous in vivo studies.