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KMID : 0545120120220030390
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Journal of Microbiology and Biotechnology
2012 Volume.22 No. 3 p.390 ~ p.399
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Cloning, Expression, and Characterization of Endoglucanase Gene egIV from Trichoderma viride AS 3.3711
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Xiaomei Huang
Jinxia Fan
Qian Yang
Xiuling Chen
Zhihua Liu
Yun Wang
Daqing Wang
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Abstract
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Endoglucanase gene egIV was cloned from Trichoderma viride AS 3.3711, an important cellulose-producing fungus, by using an RT-PCR protocol. The egIV cDNA is 1,297 bp in length and contains a 1,035 bp open reading frame encoding a 344 amino acid protein with an estimated molecular mass of 35.5 kDa and isoelectronic point (pI) of 5.29. The expression of gene egIV in T. viride AS 3.3711 could be induced by sucrose, corn straw, carboxymethylcellulose (CMC), or microcrystalline cellulose, but especially by CMC. The transcripts of egIV were regulated under these substrates, but the expression level of the egIV gene could be inhibited by glucose and fructose. Three recombinant vectors, pYES2-xegIV, pYES2Mα-egIV, and pYES2Mα-xegIV, were constructed to express the egIV gene in Saccharomyces cerevisiae H158. The CMCase activity of yeast transformants IpYES2Mα-xegIV was higher than that of transformant IpYES2-xegIV or IpYES2Mα-egIV, with the highest activity of 0.13 U/ml at induction for 48 h, illustrating that the modified egIV gene could enhance CMCase activity and that MFα signal peptide from S. cerevisiae could regulate exogenous gene expression more effectively in S. cerevisiae. The recombinant EGIV enzyme was stable at pH 3.5 to 7.5 and temperature of 35oC to 65oC. The optimal reaction condition for EGIV enzyme activity was at the temperature of 55oC, pH of 5.0, 0.75 mM Ba2+, and using CMC as substrate. Under these conditions, the highest activity of EGIV enzyme in transformant IpYES2Mα-xegIV was 0.18 U/ml. These properties would provide technical parameters for utilizing cellulose in industrial bioethanol production.
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KEYWORD
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Trichoderma viride, endoglucanase EGIV, gene cloning, yeast expression
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