Role of SUC2 gene and invertase of Saccharomyces sp. W0 in inulin hydrolysis

• The SUC2 gene in Saccharomyces sp. W0 was removed.
• The disruptant W4 could not produce invertase and inulin was not hydrolyzed.
• The SUC2 gene was over-expressed in the disruptant W4.
• The recombinant yeast strain Suc2-1 produced higher invertase and more inulin was hydrolyzed.

After a SUC2 gene in Saccharomyces sp. W0, isolated from fermented rice was removed, the disruptant W4 obtained could not produce any invertase, even could not grow in the media containing sucrose and inulin, but could grow in the medium containing fructose. At the same time, inulin was not hydrolyzed by the disruptant. However, after the SUC2 gene was over-expressed in the disruptant W4, the recombinant yeast strain Suc2-1 obtained could produce much higher invertase activity than Saccharomyces sp. W0 and more inulin was hydrolyzed and the transcriptional level of the SUC2 gene in the recombinant yeast strain Suc2-1 was also much higher than that in Saccharomyces sp. W0. This is the first time to report that the SUC2 gene in Saccharomyces sp. W0 is closely related to both invertase activity and inulin hydrolysis. The invertase over-produced by the recombinant yeast strain Suc2-1 could actively convert inulin into monosaccharides. The recombinant yeast strain Suc2-1 over-expressing the SUC2 gene could produce over 13.4% (v/v) ethanol from 300.0 g/L inulin directly, suggesting that Saccharomyces sp. W0 over-producing invertase also can be applied to ethanol fermentation industry.

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