Regulation of the production of hemicellulolytic and cellulolytic enzymes by a Streptomyces sp. growing on lignocellulose

Abstract

A Streptomyces sp. isolated from compost degraded the hemicellulose fraction of straw efficiently but apparently not native cellulose. Ball-milled straw induced endoglucanase, beta-glucosidase, beta-xylanase and beta-xylosidase. Carboxymethylcellulose, cellotetraose and cellotriose induced cellulolytic enzymes specifically whereas cellobiose acted as inducer for beta-glucosidase only. Cellotriose and cellotetraose induced beta-glucosidase, but only partially induced endoglucanase. Hemicellulose (in the form of xylan) and xylobiose induced only beta-xylanase and beta-xylosidase. Kraft lignin and syringic acid induced beta-xylanase and endoglucanase but not the other enzymes. 3,4-Dimethoxycinnamic acid slightly induced beta-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 beta-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 beta-xylanase activity. Two acidic components (pI 3.55 and 3.75) displayed endoglucanase activity.