Cloning inescherichia coliof a bi‐functional cellulase/xylanase enzyme fromruminococcus flavefaciensFD‐1

Abstract
A genomic library of Ruminococcus fl avef aciens FD‐1 DNA was constructed using the Escherichia coli bacteriophage λ vector λDASH. A recombinant phage exhibiting activity against both Ostazin brilliant red‐hydroxyethyl cellulose (OBR‐HEC) and carboxymethyl cellulose (CMC) was isolated. This clone (designated FD1‐1) was further analyzed by restriction endonuclease mapping and Southern blot analysis. Substrate specificity data shows that the cloned gene(s) encodes both endoglucanase activity and endoxylanase activity. CMC and xylan zymograms of protein(s) produced by this clone and then separated by non‐denaturing PAGE suggest that the endoglucanase/endoxylanase activities reside on the same polypeptide or protein complex. An additional xylanase product lacking CMCase activity was also detected.