Genome shuffling of Hansenula anomala to improve flavour formation of soy sauce.

Genome shuffling of mutagenized Hansenula anomala was used to improve soy-sauce flavour by enhancing its salt-tolerance, because the concentration of salt was about 17% in high-salt liquid fermentation of soy sauce. A mutant strain H3-8, with stronger resistance to salt, was selected and screened after three rounds of genome shuffling. It was found that H3-8 could grow in YPD media containing a high salt content and within a wide range of pH. In high-salt liquid fermentation, the soy-sauce flavour components produced by H3-8 were distinctly improved compared with the control strains Zygosaccharomyces rouxii and Torulopsis versatilis. Notably, hydroxyethylmethylfuranone produced by H3-8 was 6.3 times as high as that formed by Z. rouxii. Ethyl acetate synthesized by H3-8 was 734 times higher than that yielded by T. versatilis. Another important aroma component, 4-ethylguaiacol was increased by up to 10.84% compared with T. versatilis.