Identification and Characterization of Two Novel Thermostable and Thermoresistant Esterases Isolated from Rice Rhizosphere by Activity- Based on Metagenomic Screening

Abstract

A 72,000 recombinant phages metagenomic library was constructed from rice rhizosphere. An esterase screening was performed and resulted in the identification of 6 positive esterase clones. Two of them, Ela1 and Ela2, were selected for a further characterization. Sequence analysis revealed that Ela1 exhibits a high homology with proteins annotated as acetyl xylan esterase (AXE) and Ela2 with SGNH hydrolases. Both enzymes are carboxylic ester hydrolases, with a high stability, an alkaline optimum pH 8-9 and active at high temperatures (75°C). Additionally, a 16S rRNA library was performed in order to characterize the biodiversity and biological diversity of the ecosystem source of this gene. It confirmed the predominance of thermophilic groups of bacteria matching with the esterases Ela1 and Ela2 annotation results and biochemical characterization. Thus, rice rhizosphere, which is a high-pressure selective ecosystem, arises as a very appropriate source of novel enzymes with a great potential for biotechnological and industrial applications.