Abstract
With the ultimate goal of identifying robust cellulases for industrial biocatalytic conversions, we have isolated and characterized a new thermostable and very halotolerant GH5 cellulase. This new enzyme, termed CelDZ1, was identified by bioinformatic analysis from the genome of a polysaccharide-enrichment culture isolate, initiated from material collected from an Icelandic hot spring. Biochemical characterization of CelDZ1 revealed that it is a glycoside hydrolase with optimal activity at 70°C and pH 5.0 that exhibits good thermostability, high halotolerance at near-saturating salt concentrations, and resistance towards metal ions and other denaturing agents. X-ray crystallography of the new enzyme showed that CelDZ1 is the first reported cellulase structure that lacks the defined sugar-binding 2 subsite and revealed structural features which provide potential explanations of its biochemical characteristics.
Highlights
Cellulose is the most abundant biopolymer on Earth, with about 100–1000 trillion tons being naturally produced in the form of plant biomass every year [1, 2]
We identified a new thermostable and extremely halotolerant glycosyl hydrolase family 5 (GH5) cellulase, termed CelDZ1
The sequencing reads were assigned to taxa using the MEtaGenome ANalyzer (MEGAN) [21], which assigned the reads to either Thermoanaerobacterium thermosaccharolyticum or Thermoanaerobacterium xylanolyticum, thereby verifying that the gene originates from a Thermoanaerobacterium species
Summary
Cellulose is the most abundant biopolymer on Earth, with about 100–1000 trillion tons being naturally produced in the form of plant biomass every year [1, 2]. It is considered to be an almost inexhaustible source of raw material, which can be transformed through biotechnologybased manipulations to environmentally friendly products of high value, such as papers, textiles, animal feed stocks, biofuels and others [3]. Cellulose is a polymer of simple composition, comprised of D-glucose units connected with β-1,4 glycosidic bonds [4]. Tight packing of these linear chains and the formation of a rigid crystalline structure make cellulose an extremely difficult starting material, which is resistant to decomposition. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript
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