Publication

Molecular cloning, expression, and characterization of four novel thermo-alkaliphilic enzymes retrieved from a metagenomic library

Maruthamuthu, M. & van Elsas, J. D., 2-Jun-2017, In : Biotechnology for Biofuels. 10, 17 p., 142.

Research output: Contribution to journalArticleAcademicpeer-review

Background: Enzyme discovery is a promising approach to aid in the deconstruction of recalcitrant plant biomass in an industrial process. Novel enzymes can be readily discovered by applying metagenomics on whole microbiomes. Our goal was to select, examine, and characterize eight novel glycoside hydrolases that were previously detected in metagenomic libraries, to serve biotechnological applications with high performance.

Results: Here, eight glycosyl hydrolase family candidate genes were selected from metagenomes of wheat straw-degrading microbial consortia using molecular cloning and subsequent gene expression studies in Escherichia coli. Four of the eight enzymes had significant activities on either pNP-beta-D-galactopyranoside, pNP-beta-D-xylopyranoside, pNP-alpha-l-arabinopyranoside or pNP-alpha-D-glucopyranoside. These proteins, denoted as proteins 1, 2, 5 and 6, were his-tag purified and their nature and activities further characterized using molecular and activity screens with the pNP-labeled substrates. Proteins 1 and 2 showed high homologies with (1) a beta-galactosidase (74%) and (2) a beta-xylosidase (84%), whereas the remaining two (5 and 6) were homologous with proteins reported as a diguanylate cyclase and an aquaporin, respectively. The beta-galactosidase- and beta-xylosidase-like proteins 1 and 2 were confirmed as being responsible for previously found thermo-alkaliphilic glycosidase activities of extracts of E. coli carrying the respective source fosmids. Remarkably, the beta-xylosidase-like protein 2 showed activities with both pNP-Xyl and pNP-Ara in the temperature range 40-50 degrees C and pH range 8.0-10.0. Moreover, proteins 5 and 6 showed thermotolerant alpha-glucosidase activity at pH 10.0. In silico structure prediction of protein 5 revealed the presence of a potential "GGDEF" catalytic site, encoding alpha-glucosidase activity, whereas that of protein 6 showed a "GDSL" site, encoding a 'new family' alpha-glucosidase activity.

Conclusion: Using a rational screening approach, we identified and characterized four thermo-alkaliphilic glycosyl hydrolases that have the potential to serve as constituents of enzyme cocktails that produce sugars from lignocellulosic plant remains.

Original languageEnglish
Article number142
Number of pages17
JournalBiotechnology for Biofuels
Volume10
Publication statusPublished - 2-Jun-2017

    Keywords

  • Recombinant glycoside hydrolases, Thermo-alkaliphilic enzymes, Galactosidase, Biomass pretreatment, Biotechnological application, ACTIVE BETA-GALACTOSIDASE, GENE CLONING, LIGNOCELLULOSIC MATERIALS, FUNCTIONAL METAGENOMICS, CAULOBACTER-CRESCENTUS, CARBOHYDRATE ESTERASES, MICROBIAL XYLANASES, BIOFILM FORMATION, DI-GMP, FAMILY

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