Improvement of soy-sauce flavour by genome shuffling in Candida versatilis to improve salt stress resistance

Genome shuffling of Candida versatilis was applied to improve the soy-sauce flavour by further increasing salt stress resistance. A mutant S3-5, with a stronger resistance to salt, was isolated after three rounds of genome shuffling. It is found that S3-5 improved stress tolerance to higher potassium chloride and lithium chloride. S3-5 not only grew well in the YPD (peptone, yeast extract and dextrose) medium containing high concentrations of sodium chloride with various pH values, but also exhibited improvement of growth ability in soy-sauce medium. The main aroma compounds in soy sauce were distinctly improved. Notably, S3-5 produced about 2.78 times as much ethanol as the control strain. Another important aroma compound, 4-hydroxy-2 (or 5)-ethyl-5 (or 2)-methyl-3 (2H)-furanone (HEMF) was enhanced by up to 80%. Meanwhile, S3-5 accelerated flavour formation of soy sauce thus decreasing the total time required for the aroma development.