Production of xylanases by Streptomyces species and their bleaching effect on rice straw pulp

摘要

The number of potential applications of microbial xylanases in the pulp and paper industry is gradually increasing and several are approaching commercial use. This industry needs a xylanase, which is free of cellulase. Twenty isolated Streptomycetes strains from Egyptian soils, which produce cellulase free-xylanase and are easily grown using a low-cost agriculture waste substrate, were investigated. The two most active strains have been identified as Streptomyces albus and Streptomyces chromofuscus. Their maximum xylanase activity was 13.25, 19.31 and 32.53, 43.01 on untreated rice straw pulp and pulp treated with TiO2 in both Streptomyces species respectively. The enzyme activity increased when both isolates were grown on yeast extract. Optimum production of xylanase was recorded after five days of fermentation. Xylanase produced with Streptomyces chromofuscus showed higher bleaching activity than that from Streptomyces albus. The enzyme enhanced the liberation of reducing sugars, which improved pulp bleachability