Production and partial characterization of alkali-tolerant xylanase from an alkalophilic <i style="">Streptomyces</i> sp. CD3

Abstract

Of the 30 isolates screened, <i style="">Streptomyces</i> sp CD3, an alkalophilic isolate, showed maximum xylanase production. Organism efficiently used wheat bran and bagasse as substrates and produced 2.211 and 1.896 U/ml of xylanase, respectively. Soybean meal supplementation enhanced xylanase production substantially, while yeast extract and gelatin did so moderately. Although, optimum enzyme activity was at pH 8 and temperature (50^oC), but enzyme retained considerable activity at higher pH (80% at 9-10) and temperature (60 % at 70-90^oC). The enzyme was strongly inhibited by Hg²⁺, while Fe³⁺, Ca²⁺ and Zn²⁺ were slight inducers of xylanase. Zymogram analysis suggested the presence of three xylanases (mol wt, 69.18, 63.09 & 43.65 kDa). Purification (108-fold) was achieved by carboxymethyl sephadex chromatography. Enzyme obeyed Michaelis-Menten kinetics (K_m 3.9 mg/ml). Industrially desirable characteristics of the enzyme like thermostability and alkali-stability, and highly alkalophilic nature of the organism, and its ability to grow and produce enzyme on low value agricultural by-products reflects the potential commercial importance of this study.