Cloning, sequence analysis, and expression in Escherichia coli of a gene coding for a β-mannanase from the extremely thermophilic bacterium 'Caldocellum saccharolyticum'

A λ recombinant phage expressing β-mannanase activity in Escherichia coli has been isolated from a genomnic library of the extremely thermophilic anaerobe 'Caldocellum saccharolyticum.' The gene was cloned into pBR322 on a 5-kb BamHI fragmnent, and its location was obtained by deletion analysis. The sequence of a 2.1-kb fragment containing the mannanase gene has been determined. One open reading frame was found which could code for a protein of M(r) 38,904. The mannanase gene (manA) was overexpressed in E. coli by cloning the gene downstream from the lacZ promoter of pUC18. The enzyme was most active at pH 6 and 80°C and degraded locust bean gum, guar gum, Pinus radiata glucomannan, and konjak glucomannan. The noncoding region downstream from the mannanase gene showed strong homology to celB, a gene coding for a cellulase from the same organism, suggesting that the manA gene might have been inserted into its present position on the 'C. saccharolyticum' genome by homologous recombination.