Título :	Isolation of xylose isomerases by sequence- and function-based screening from a soil metagenomic library
Autor :	Parachin, Nádia Skorupa Grauslund, Marie F. Gorwa
Assunto::	Xilose Saccharomyces cerevisiae Fungos Basctérias
Fecha de publicación :	5-may-2011
Editorial :	BioMed Central
Citación :	PARACHIN, Nádia Skorupa; GRAUSLUND, Marie F. Gorwa. Isolation of xylose isomerases by sequence- and function-based screening from a soil metagenomic library. Biotechnology for Biofuels, v. 4, Article 9, 5 mai. 2011. Disponível em: <https://biotechnologyforbiofuels.biomedcentral.com/articles/10.1186/1754-6834-4-9>. Acesso em: 26 jun. 2017. doi: https://biotechnologyforbiofuels.biomedcentral.com/articles/10.1186/1754-6834-4-9.
Abstract:	Background: Xylose isomerase (XI) catalyses the isomerisation of xylose to xylulose in bacteria and some fungi. Currently, only a limited number of XI genes have been functionally expressed in Saccharomyces cerevisiae, the microorganism of choice for lignocellulosic ethanol production. The objective of the present study was to search for novel XI genes in the vastly diverse microbial habitat present in soil. As the exploitation of microbial diversity is impaired by the ability to cultivate soil microorganisms under standard laboratory conditions, a metagenomic approach, consisting of total DNA extraction from a given environment followed by cloning of DNA into suitable vectors, was undertaken. Results: A soil metagenomic library was constructed and two screening methods based on protein sequence similarity and enzyme activity were investigated to isolate novel XI encoding genes. These two screening approaches identified the xym1 and xym2 genes, respectively. Sequence and phylogenetic analyses revealed that the genes shared 67% similarity and belonged to different bacterial groups. When xym1 and xym2 were overexpressed in a xylA-deficient Escherichia coli strain, similar growth rates to those in which the Piromyces XI gene was expressed were obtained. However, expression in S. cerevisiae resulted in only one-fourth the growth rate of that obtained for the strain expressing the Piromyces XI gene. Conclusions: For the first time, the screening of a soil metagenomic library in E. coli resulted in the successful isolation of two active XIs. However, the discrepancy between XI enzyme performance in E. coli and S. cerevisiae suggests that future screening for XI activity from soil should be pursued directly using yeast as a host.
Licença::	© 2011 Parachin and Gorwa-Grauslund; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
DOI:	https://dx.doi.org/10.1186/1754-6834-4-9
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