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Abstract
A Streptomyces sp. isolated from compost degraded the hemicellulose fraction of straw efficiently but apparently not native cellulose. Ball-milled straw induced endoglucanase, β-glucosidase, β-xylanase and β-xylosidase. Carboxymethylcellulose, cellotetraose and cellotriose induced cellulolytic enzymes specifically whereas cellobiose acted as inducer for β-glucosidase only. Cellotriose and cellotetraose induced β-glucosidase, but only partially induced endoglucanase. Hemicellulose (in the form of xylan) and xylobiose induced only β-xylanase and β-xylosidase. Kraft lignin and syringic acid induced β-xylanase and endoglucanase but not the other enzymes. 3,4-Dimethoxycinnamic acid slightly induced β-xylanase whereas 3,5-dimethoxy-4-hydroxycinnamic acid specifically induced endoglucanase. Neither veratric acid nor vanillic and ferulic acids induced any of the cellulolytic or hemicellulolytic enzymes. Enzyme production was subject to a form of carbon catabolite repression. Endoglucanase and β-xylanase were excreted into the culture medium. Four protein components, one acidic (pI 5·2) and three basic (pI 8·15, 8·45 and 8·65) exhibited β-xylanase activity. Two acidic components (pI 3·55 and 3·75) displayed endoglucanase activity.
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