title: Hyperexpression of two Aspergillus Niger Xylanase Genes in Escherichia Coli and Characterization of the Gene Products.
abstract: The analysis of individual gene product should enable to clarify the role of a particular enzyme in a complex xylanase system of A. niger. The two genes encoding precursors of co-produced endo-1,4-β-D-xylanases, xynA1 and xynB, were isolated from Aspergillus niger SCTCC 400264 (SCTCC, China) by using RT-PCR technique and then successfully expressed in Escherichia coli BL21. The nucleotide sequences of the xynA1 and xynB genes revealed that they were only 52.5% homology to each other. Characterization of the recombinant enzymes revealed the different properties: the specific activity of recombinant XYNA1 was 16.58 U/mg compared to 1201.7 U/mg for recombinant XYNB; The optimum temperature and pH of the recombinant XYNA1 were 35 °C and 3.0, respectively, whereas the corresponding values for the recombinant XYNB were 55 °C and 5.0, respectively; The recombinant XYNB showed much more thermostability than recombinant XYNA1; The recombinant XYNB showed 94% of maximal activity after incubating in water for 60 min at 60 °C compared to no activity for recombinant XYNA1. Various metal ions had different effects on activity between the two recombinant xylanases.
authors.affiliation: College of Life Science , Sichuan University, Chengdu 610064 , China ; Microbiology and Metabolic Engineering key Laboratory of Sichuan Province , Chengdu 610064 , China.
authors.forename: Xiuli
authors.initials: X
authors.lastname: Yi
authors.forename: Yan
authors.initials: Y
authors.lastname: Shi
authors.forename: Hui
authors.initials: H
authors.lastname: Xu
authors.forename: Wei
authors.initials: W
authors.lastname: Li
authors.forename: Jie
authors.initials: J
authors.lastname: Xie
authors.forename: Rongqing
authors.initials: R
authors.lastname: Yu
authors.forename: Jun
authors.initials: J
authors.lastname: Zhu
authors.forename: Yi
authors.initials: Y
authors.lastname: Cao
authors.forename: Dairong
authors.initials: D
authors.lastname: Qiao
keywords: Aspergillus niger; enzymatic characterization; prokaryotic expression; xylanase
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