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Usage of Enzyme Substrate to Protect the Activities of Cellulase, Protease and a-Amylase in Simulations of Monogastric Animal and Avian Sequential Total Tract Digestion

H. T. Wang, J. T. Hsu
2006 Asian-Australasian Journal of Animal Sciences  
Many polysaccharides can form viscous gel-like structure in the small intestine which will trap nutrients and hinder the action of the animal's digestive enzymes. Cellulases and xylanases added to the diet can break down these gels and release the trapped nutrients (Pettersson and Aman, 1989) . However, positive responses were not achieved all the time for fibrolytic enzymes' application in pigs or broilers (Kim et al., 2004; Qiao et al., 2005) . Some cellulases, expressed by bacteria and
more » ... bacteria and fungi, are glycosylated by post-translational modification which often protects enzymes from inactivation by heat or protease (Olsen and Thomsen, 1991) . The stability of cellulase can also be improved by modification with synthetic copolymers over a wide range of pH (Jin, 1996) . Fontes et al. (1995) indicated that labile cellulases were resistant to proteolytic attack in the presence of their appropriate substrate. Many commercial feed enzyme additives are mixtures of protease, cellulase and amylase. In this case, protease may attack other enzymes and decrease their efficiency. To be fully functional in the digestive tract, exogenous enzymes should be resistant to attack of protease in the small intestine, and able to exhibit catalytic activity in the pH range 6 to 8. To maintain the activity of exogenous enzymes, substrate addition seems to be a convenient and cheap method to protect enzymes. In this study, purified microbial protease, cellulase and amylase were used alone or mixed for various tests of substrates' protection ability. Common protease substrates (casein, gelatin or soybean protein), cellulase Asian-Aust. ABSTRACT : Cellulase from Aspergillus niger, (α-amylase from Bacillus sp. and protease from Bacillus globigii were used as enzyme sources in this study to examine how their respective substrates protect them in two kinds of simulated gastrointestinal tract digesting processes. Avian total digest tract simulation test showed that filter paper, Avicel and cellulose resulted in 7.7, 6.4 and 7.4 times more activity than of unprotected cellulose, respectively. Protease with addition of casein, gelatin or soybean protein showed no significant protection response. Starch protected amylase to be 2.5 times activity of the unprotected one. Monogastric animal total tract digestion simulation test showed that filter paper, Avicel and cellulose resulted in 5.9, 9.0 and 8.8 times activity of unprotected cellulase, respectively. Casein, gelatin and soybean protein resulted in 1.2, 1.3 and 2.0 times activity of unprotected protease, respectively. Starch did not protect amylase activity in monogastric animal total tract simulation. Protection of mixed enzymes by substrates in two animal total tract simulation tests showed that filter paper in combination with soybean protein resulted in 1.5 times activity of unprotected cellulose, but all substrates tested showed no significant protection effect to protease. Soybean protein and starch added at the same time protected the amylase activity to be two times of the unprotected one. Test of non-purified substrate protection in two animal total digest tract simulation showed that cellulase activity increased as BSA (bovine serum albumin) concentration increased, with the highest activity to be 1.3 times of unprotected enzyme. However, BSA showed no significant protection effect to protease. Amylase activity increased to 1.5 times as BSA added more than 1.5% (w/v). Cellulase activity increased to 1.5 times as soybean hull was added higher than 1.5%. Amylase had a significant protection response only when soybean hull added up to 2%. Protease activity was not protected by soybean hull to any significant extent. (
doi:10.5713/ajas.2006.1164 fatcat:rbyaca7w75cvxltguh53wag3by