A gene encoding a β-mannanase (manA) has been cloned from an obligately anaerobic extreme thermophile, Caldicellulosiruptor strain Rt8B.4, which is most closely related to Caldicellulosiruptor saccharolyticus (formerly Caldocellum saccharolyticum). The gene codes for a multidomain enzyme with a C-terminal β-mannanase domain which was amplified by the polymerase chain reaction and cloned into a temperature-inducible expression vector in Escherichia coli. Sequence comparisons have shown that the Man domain of Rt8B.4 ManA is related to a thermophilic Dictyoglomus mannanase and a mesophilic mannanase from a Bacillus species. It appears to be unrelated to the β-mannanase domain of C. saccharolyticus, implying acquisition of the genes from unrelated sources by the two bacteria.
- pulp bleaching