An endo-beta-1,4-xylanase from Rhizopus oryzae: production, partial purification and biochemical characterization

An endoxylanase (1,4-beta -D-xylan xylanohydrolase, EC 3.2.1.8) was produce d by Rhizopus oryzae fermentation. Different xylan-containing agricultural byproducts such as wheat straw, wheat stems, cotton bagasse, hazelnut shell s, corn cobs and oat sawdust were used as the carbon source, white soybean bagasse was used as both the nitrogen and carbon source in the enzyme produ ction medium. Partial steam hydrolysis of the agricultural byproducts incre ased the enzyme yield of the microorganism, The highest xylanase activity, 260 IU/ml fermentation medium, was obtained by using a medium containing 3% hydrolyzed com cobs, 1% hydrolyzed soybean bagasse, 1% ammonium sulfate an d 0.5% sodium chloride at 35 degreesC, pH 5, 350 rpm and under aerobic cond itions in a 2-1 fermenter. A maximal cellulose activity of 0.06 IU/ml was o bserved. The enzyme was partially purified from the culture medium by ammon ium sulfate precipitation and cation exchange filtration. A 55-fold purific ation was achieved, with the purified xylanase having a specific activity o f about 50 IU/mg protein. The molecular weight of the enzyme is about 22 kD a by SDS-PAGE. The optimal pH and temperature values of the enzyme were abo ut 4.5 and 55 degreesC, respectively. The enzyme obeys Michaelis-Menten kin etics with Km and V. values being 18.5 mg xylan/ml and 90 IU/mg protein, re spectively. (C) 2001 Elsevier Science Inc. All rights reserved.