Fractionation of crude pentosanase (arabinoxylanase) for improvement of the nutritional value of rye diets for broiler chickens

Abstract

AbstractA pentosanase component of a crude enzyme product was concentrated and added to chick diets. Four levels of purity were examined: (a) the crude enzyme product, (b) a crude water extract, (c) a pentosanase purified using ion‐exchange chromatography (non‐bound fraction), and (d) residual pentosanase eluted with 0·4 M NaCl salt from the ion‐exchange column (salt‐eluted fraction). All preparations exhibited high viscosity‐reduction capabilities when tested against a soluble pentosan preparation isolated from rye grain. The absence of arabinose release during rapid viscosity reduction of pentosan indicated that the non‐bound pentosanase was an endoxylanase (1,4‐β‐D‐xylan xylanohydrolase, EC 3.2.1.8) without α‐L‐arabino‐furanosidase activity. When added to broiler chick diets containing rye as the only cereal, all enzyme preparations significantly improved growth and feed conversion. At equivalent viscosity‐reduction activity the non‐bound pentosanase was less effective than other preparations, suggesting that multiple enzymes may be necessary to elicit maximum benefit. Alternatively, since the non‐bound enzyme was less pH stable it may have lost activity in the acidic environment of the foregut.