title: Identification and characterization of novel cellulolytic and hemicellulolytic genes and enzymes derived from German grassland soil metagenomes.
abstract: Soil metagenomes represent an unlimited resource for the discovery of novel biocatalysts from soil microorganisms. Three large-inserts metagenomic DNA libraries were constructed from different grassland soil samples and screened for genes conferring cellulase or xylanase activity. Function-driven screening identified a novel cellulase-encoding gene (cel01) and two xylanase-encoding genes (xyn01 and xyn02). From sequence and protein domain analyses, Cel01 (831 amino acids) belongs to glycoside hydrolase family 9 whereas Xyn01 (170 amino acids) and Xyn02 (255 amino acids) are members of glycoside hydrolase family 11. Cel01 harbors a family 9 carbohydrate-binding module, previously found only in xylanases. Both Xyn01 and Xyn02 were most active at 60°C with high activities from 4 to 10 and optimal at pH 7 (Xyn01) and pH 6 (Xyn02). The cellulase gene, cel01, was expressed in E. coli BL21 and the recombinant enzyme (91.9 kDa) was purified. Cel01 exhibited high activity with soluble cellulose substrates containing β-1,4-linkages. Activity with microcrystalline cellulose was not detected. These data, together with the analysis of the degradation profiles of carboxymethyl cellulose and barley glucan indicated that Cel01 is an endo 1,4-β-glucanase. Cel01 showed optimal activity at 50°C and pH 7 being highly active from pH range 5 to 9 and possesses remarkable halotolerance.
authors.affiliation: Department of Genomic and Applied Microbiology, Göttingen Genomics Laboratory, Institute of Microbiology and Genetics, Georg-August University Göttingen, Grisebachstr. 8, 37077, Göttingen, Germany.
authors.forename: Heiko
authors.initials: H
authors.lastname: Nacke
authors.forename: Martin
authors.initials: M
authors.lastname: Engelhaupt
authors.forename: Silja
authors.initials: S
authors.lastname: Brady
authors.forename: Christiane
authors.initials: C
authors.lastname: Fischer
authors.forename: Janine
authors.initials: J
authors.lastname: Tautzt
authors.forename: Rolf
authors.initials: R
authors.lastname: Daniel
mesh_terms: D044602:Cellulases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D003001:Cloning, Molecular; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics; D015870:Gene Expression; D015723:Gene Library; D005858:Germany; D054892:Metagenome; D008969:Molecular Sequence Data; D008970:Molecular Weight; D017422:Sequence Analysis, DNA; D012988:Soil Microbiology; D013379:Substrate Specificity; D014995:Xylosidases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*
chemical_list: D044602:Cellulases; D014995:Xylosidases