Characterization of an acetyl xylan esterase from the marine bacterium Ochrovirga pacifica and its synergism with xylanase on beechwood xylan

Sachithra Amarin Hettiarachchi,Eunyoung Jo,Mahanama De Zoysa,Do-Hyung Kang,Svini Dileepa Marasinghe,Chulhong Oh,Yoon-Hyeok Kang,Young-Kyung Kwon,Youngdeuk Lee,Tae-Yang Eom

doi:10.1186/s12934-019-1169-y

Abstract

BackgroundAcetyl xylan esterase plays an important role in the complete enzymatic hydrolysis of lignocellulosic materials. It hydrolyzes the ester linkages of acetic acid in xylan and supports and enhances the activity of xylanase. This study was conducted to identify and overexpress the acetyl xylan esterase (AXE) gene revealed by the genomic sequencing of the marine bacterium Ochrovirga pacifica.ResultsThe AXE gene has an 864-bp open reading frame that encodes 287 aa and consists of an AXE domain from aa 60 to 274. Gene was cloned to pET-16b vector and expressed the recombinant AXE (rAXE) in Escherichia coli BL21 (DE3). The predicted molecular mass was 31.75 kDa. The maximum specific activity (40.08 U/mg) was recorded at the optimal temperature and pH which were 50 °C and pH 8.0, respectively. The thermal stability assay showed that AXE maintains its residual activity almost constantly throughout and after incubation at 45 °C for 120 min. The synergism of AXE with xylanase on beechwood xylan, increased the relative activity 1.41-fold.ConclusionResulted higher relative activity of rAXE with commercially available xylanase on beechwood xylan showed its potential for the use of rAXE in industrial purposes as a de-esterification enzyme to hydrolyze xylan and hemicellulose-like complex substrates.

Highlights

Hemicellulose is the second most abundant polysaccharide type in land plant cell walls and it consisted of about 25–35% of forest and agricultural residues [1, 2]
Identification and molecular characterization of recombinant AXE (rAXE) The acetyl xylan esterase (AXE) gene has an 864-bp open reading frame that encodes 287 aa the acetyl esterase domain can be found from aa 60 to 274
This study was conducted to characterize the acetyl xylan esterase gene from the marine bacterium O. pacifica, isolated from a seaweed sample [20]. This is the first report of such an enzyme from the genus Ochrovirga, and further biochemical characterization of the expressed enzyme within an E. coli expression system was performed

Summary

Introduction

Hemicellulose is the second most abundant polysaccharide type in land plant cell walls and it consisted of about 25–35% of forest and agricultural residues [1, 2]. Hemicellulose consists of a linear backbone of β-1,4linked xyloses and short-chain branches of O-acetyl, Hettiarachchi et al Microb Cell Fact (2019) 18:122. The synergistic action of acetyl xylan esterase and endoxylanases increases the efficient hydrolysis of xylan [18, 19]. During genome sequence analysis of O. pacifica, an acetyl xylan esterase (AXE) gene was found. Acetyl xylan esterase plays an important role in the complete enzymatic hydrolysis of lignocellulosic materials. It hydrolyzes the ester linkages of acetic acid in xylan and supports and enhances the activity of xylanase. This study was conducted to identify and overexpress the acetyl xylan esterase (AXE) gene revealed by the genomic sequencing of the marine bacterium Ochrovirga pacifica

Methods

Results

Discussion

Conclusion