Abstract

One hundred and forty one actinomycetes strains were isolated from Egyptian and Saudi Arabia soils and decayed rice straw samples. The isolated actinomycetes strains were screened for their cellulolytic activities on carboxymethyl cellulose (CMC) - containing agar plates. Streptomyces sp. NEAE-D showed the highestcarboxymethyl cellulase (CMCase) activity. The optimum conditions for CMCase production were the use of pretreated rice straw as the best carbon source that supported better CMCase production than carboxymethyl cellulose after 5 days incubation at pH 6.5 and at 35°C in the presence of yeast extract as nitrogen source. Crude CMCase activity was characterized. The highest activity was recorded after 50 min incubation, at 50°C, pH 6.0 and 2% substrate concentration, the CMCase was shown to be alkali-tolerant enzyme whose activity was stable over a broad pH range (7 to 10). The enzyme retained 97.31 and 70.99% of its activity at 50 and 60°C respectively after 60 min. High performance liquid chromatography (HPLC) analysis of the hydrolysate of saccharified pretreated rice straw identified the formation of glucose, cellobiose, mannose and xylose as byproducts.

Key words: Carboxymethyl cellulase, production, pretreated  rice  straw, alkali-tolerant, Streptomyces sp. NEAE-D, characterization.