Stability of feed enzymes in physiological conditions assayed by in vitro methods

Authors

• Johan Inborr Finnfeeds International Ltd., Market House, High Street, Marlborough, Wiltshire SNB IAA, United Kingdom
• Anne Grönlund

DOI: https://doi.org/10.23986/afsci.72641

Abstract

A series of in vitro incubations were carried out to investigate the stability of two enzyme preparations in conditions similar to those in the upper gastrointestinal tract of monogastric animals. The two enzyme products, one crude xylanase from Trichoderma longibrachiatum (Multifekt K) and the other a specifically manufactured feed enzyme (Avizyme SX®), were subjected to incubations at low and neutral pH with and without proteolytic enzymes (pepsin and pancreatin). Wheat gluten was employed together with the crude xylanase to investigate its potential as a stabilising agent. Due to the buffering effect of Avizyme SX®, incubations were carried out with (pH 2.5) and without (pH 3.2) addition of either citric or hydrochloric acid. Incubation of the crude xylanase at low pH followed by incubation at neutral pH resulted in negligible loss of xylanase activity whereas β-xylosidase recovery fell to 57 per cent of the initial value (P<0.05). Addition of wheat gluten resulted in full recovery of β-xylosidase. The recoveries of both β-glucanase and xylanase were significantly (P<0.05) lower than the initial values after incubation of Avizyme SX® in pH 2.5. However, with no pH adjustment (pH 3.2) the recoveries were significantly higher (P<0.05 for β-glucanase and P<0.10 for xylanase). The results from the pepsin and pancreatin incubations showed similar trends as the ones of the pH stability experiments. Consequently, gluten addition and no pH adjustment gave the highest enzyme activity recoveries. The results suggest that partial enzyme inactivation may occur due to the low pH and proteolytic activities and hence in the Gl-tract of monogastrics. Feeds and feedstuffs can due to their buffering capacity and possibly by providing substrates for the enzymes markedly reduce the rate of inactivation. Results from a number of pig and poultry experiments appear to support this assumption. In vivo recovery measurements using animal models are needed to substantiate this.