Isolation of cold-active, acidic endocellulase from Ladakh soil by functional metagenomics

Abstract

Mining of soil sample from cold desert of Ladakh by functional metagenomics led to the isolation of cold-adapted endocellulase (CEL8M) that hydrolyses carboxymethyl cellulose (CMC). Mature CEL8M, a 347-residue polypeptide with a molecular mass of 38.9 kDa showed similarity to β-1,3-1,4 D-glucanase from Klebsiella sp. The enzyme contains the catalytic module of glycosyl hydrolase family 8 but does not possess a carbohydrate-binding domain. 3D structural model of the enzyme built by homology modeling showed an architecture of (α/α)6-barrel fold. The purified enzyme was found to be active against CMC, xylan, colloidal chitosan and lichenan but not active against avicel. Glucose was not among the initial hydrolysis products, indicating an endo mode of action. CEL8M displayed maximal activity at pH 4.5 and remained significantly active (~28 %) when the temperature decreased to 10 °C. Cold-active endocellulase CEL8M may find applications in textile industry at low temperature which can result in energy savings.

Discovery of novel enzymes with industrial potential from a cold and alkaline environment by a combination of functional metagenomics and culturing

“…Firmicutes were best with approximately 70% and Actinobacteria worst with around 10%, suggesting that E. coli could be a suitable host for the ikaite library given the high fraction of Firmicutes , although the study did not consider other limiting factors. The library constructed had relatively few clones, but the hit-rate was comparable to those of similar studies: one α-amylase was found when screening a cosmid-library of 35,000 clones [38], six esterases were identified in a screening of 60,000 fosmid clones [8], 11 cellulases were found when screening a small insert BAC-library of 10,000 clones [39], three β-galactosidases in a screening of 2,100 plasmid clones [40], one amylolytic enzyme in a screening of 30,000 plasmid clones [41], one cellulase in a plasmid library of 8,500 clones [42], and 38 amylases, 13 phosphatases but no proteases in a screening of 32,000 plasmid clones [43]. …”

Cloning, expression and characterization of a cold-adapted endo-1, 4-β-glucanase from Citrobacter farmeri A1, a symbiotic bacterium of Reticulitermes labralis

“…Based on these applications, cold-adapted EglCs have attracted increased attention (Maharana & Ray, 2015; Gerday et al, 2000). However, few cold-adapted β -glucanases have been identified and cloned to date (Bhat et al, 2013; Cavicchioli et al, 2011)…”

Structure and function of a novel GH8 endoglucanase from the bacterial cellulose synthase complex of Raoultella ornithinolytica

“…Family GH8 endoglucanases from Clostridium thermocellum [40], Bacillus circulans [41], Halomonas sp. [39] and Ladakh soil metagenome [42] showed catalytic efficiencies of 1.5, 3.7, 2.1 and 2.5 mL.mg -1 .s -1 , respectively. Based on our data, the catalytic efficiency ( k cat / K m ) of AfmE1 was 5.5 mL.mg -1 .s -1 , which is higher than what has been described for other GH8 endoglucanases so far.…”