Effects of crude feruloyl and acetyl esterase solutions of Neocallimastix sp. YQ1 and Anaeromyces sp. YQ3 isolated from Holstein steers on hydrolysis of Chinese wildrye grass hay, wheat bran, maize bran, wheat straw and corn stalks

Abstract

Neocallimastix sp. YQ1 and Anaeromyces sp. YQ3 were isolated from rumen fluids of Holstein steers using a modification of the roll-tube technique of Hungate (1969). After a 9-day incubation for YQ1, and a 4-day incubation for YQ3, with optimal carbon and N supply in cultures, crude enzyme solutions of both fungi were prepared by centrifuging cultures for 10 min at 1000 × g at 4 °C. Enzymological characteristics of ferulic acid esterase and acetyl esterase were measured in the crude enzyme solution. The Michaelis constants ( K m ) and maximum velocities ( V max ) of ferulic acid esterase against methyl ferulate at pH 6.0 and 39 °C were 30 μM and 8.05 mU for YQ1 and 129 μM and 3.15 mU for YQ3, respectively. With substrate of p-nitrophenyl acetate, the K m and V max of AE at pH 6.0 and 39 °C were 0.21 mM and 336 mU for YQ1 and 5.26 mM and 854 mU for YQ3. Enzymatic release of reducing sugar, ferulic acid, and p-coumaric acid from complex fibre-rich feedstuffs was evaluated, and YQ3 released more reducing sugars from wheat straw, but less from the other plant materials especially maize bran and corn stalks. YQ3 liberated much more hydroxycinnamic acids from corn stalks, and YQ1 liberated much more hydroxycinnamic acids from maize bran. Anaerobic rumen fungi showed species diversity of enzymological characteristics of ferulic acid esterase and acetyl ester esterase, and exhibited a strong capability to release ferulic acid and p-coumaric acid from complex fibre-rich feedstuffs. Therefore anaerobic fungi, especially their FAE, should not be neglected in studies on biodegradation of plant cell walls in the rumen as well as on industrial processes developed to release ferulic acid and p-coumaric acid from agricultural by-products with potential commercial industrial applications, such as precursors of natural vanillin, natural antioxidants, food preservative agents, anti-inflammatory agents and photoprotectants.