A genomic library ofRuminococcus albus 8 DNA was constructed by using the Escherichia coli bacteriophage
XDASH. Recombinants were screened for celiulolytic activity by plating in soft agar (0.7%) overlays containing
either 1% (wt/vol) carboxymethyl cellulose (CMC), 4-methylumbelliferyl-I(-D-cellobioside (MUC, 1 mg/ml), or
1% (wt/vol) Ostazin brilliant red-hydroxyethyl cellulose (OBR-HEC). One hundred and three recombinant
phage exhibiting activity against OBR-HEC were found, and these fell into different classes based on the size
of the zone of hydrolysis. Twenty-one recombinant phage exhibiting activity against CMC and 19 recombinant
phage exhibiting activity against MUC were isolated. Four OBR-HEC+, five CMC+, and seven MUC+ clones
were further analyzed by restriction endonuclease mapping and cellulase substrate specificity to identify unique
clones and to determine their cellulase type. Three different clone types representing endoglucanase activity
were identified. Three clones that appeared to encode exoglucanase type activity and four clones that had a
mixed specificity, including ,-glucosidase activity, were also identified.