Heterologous co-production of <Emphasis Type="Italic">Thermobifida fusca</Emphasis> Cel9A with other cellulases in <Emphasis Type="Italic">Saccharomyces cerevisiae</Emphasis> |
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Authors: | Niel van Wyk Riaan den Haan Willem H van Zyl |
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Institution: | (1) Department of Microbiology, University of Stellenbosch, De Beer Street, Stellenbosch, 7600, South Africa; |
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Abstract: | The processive endoglucanase Cel9A of the moderately thermophilic actinomycete Thermobifida fusca was functionally produced in Saccharomyces cerevisiae. Recombinant Cel9A displayed activity on both soluble (carboxymethylcellulose) and insoluble (Avicel) cellulose substrates
confirming its processive endoglucanase activity. High-performance anionic exchange chromatography analyses of soluble sugars
released from Avicel revealed a cellobiose/glucose ratio of 2.5 ± 0.1. Growth by the recombinant strain on amorphous cellulose
was possible due to the sufficient amount of glucose cleaved from the cellulose chain. This is the first confirmed report
of S. cerevisiae growing on a cellulosic substrate as sole carbohydrate source while only expressing one recombinant gene. To improve the
cellulolytic capability of S. cerevisiae and to investigate the level of synergy among cellulases produced by a recombinant host, the cel9A gene was co-expressed with four cellulase-coding genes of Trichoderma reesei: two endoglucanases cel5A (egII) and cel7B (egI), and two cellobiohydrolases cel6A (cbhII) and cel7A (cbhI). Synergy, especially between the Cel9A and the two cellobiohydrolases, resulted in a higher cellulolytic capability of the
recombinant host. |
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