Production and partial characterization of alkali-tolerant xylanase from an alkalophilic Streptomyces sp. CD3

摘要

Of the 30 isolates screened, Streptomyces 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℃), but enzyme retained considerable activity at higher pH (80% at 9-10) and temperature (60 % at 70-90℃). The enzyme was strongly inhibited by Hg~(2+), while Fe~(3+), Ca~(2+) and Zn~(2+) 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.