Over-expression of SSU1 gene improves the sulfur resistance of Saccharomyces uvarum

Saccharomyces uvarum is a good wine yeast species for Sauvignon Blanc, which also may have great potential for the other fruit wine industry. However, the sulfur tolerance of most S. uvarum strains is very poor. To get sulfur tolerant S. uvarum strains, an expression vector that contained SSU1 gene from a sulfite tolerant strain A9 was constructed and was transferred into sulfite-sensitive strains ACY338 and A4, then ten colonies of transformation candidates from each starting strain were selected, and grown in the sulfite contained culture medium, screened with specific PCR products. The PCR products were sequenced, and results showed that all candidate transformations contained the exogenous SSU1 gene from sulfite tolerant strain A9. The SO
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average output of transformations of ACY338 and A4 increased 267.5% and 362.0% than that of the starting strains, respectively, while the difference of H
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S production among transformations and the starting strains was small. Fermentation measurement showed that selected transformations ACY338 - SSU1-5 and A4 - SSU1- 17 could ferment very well in grape juice containing 15 mM sodium sulfite. Hence, the SSU1 gene was important to sulfite resistance of S. uvarum strains, and over-expression of it could promote the sulfite resistance was concluded. This is the first report on getting transgenic S. uvarum strains for sulfur resistance using sulfite-sensitive genotypes.