Impact of ARTP mutagenesis on the selection of salt-tolerant, aroma-producing yeasts and their contribution to the flavor of fermented soy sauce

The ARTP (atmospheric and room temperature plasma) mutation breeding approach was employed to enhance the salt tolerance and metabolic capability of Torulopsis versatilis . Targeted screening for salt tolerance identified the positive mutant strain T20-3, which exhibited improved performance in media 18 % and 20 % salinity. The selected strain's genetic stability, metabolic performance, and fermentation characteristics were further evaluated through successive passaging and mash fermentation experiments. The results demonstrated that T20-3 yeast could maintain stable propagation under high salt conditions and exhibited robust flavor production through enhanced glycolysis, amino acid metabolism, and fatty acid metabolism pathways. During the fermentation of T20-3, the content of alcohols and esters was elevated by 95.28 % and 201.83 %, with a significant increase in isoamyl acetate and phenylethanol. The combination of headspace solid-phase microextraction gas chromatography-mass spectrometry (HS-SPME-GC-MS) analysis and sensory evaluation demonstrated that increased levels of key flavor compounds, including phenylethanol, acetic acid, isoamyl acetate, 3-hydroxy-2-butanone, and 2,3,5-trimethylpyrazine, contributed to a more pronounced floral, fruity, and sauce-like flavor profile in T20-3 soy sauce. In conclusion, the findings indicated that T20-3 enhanced the flavor quality of fermented soy sauce and holds considerable potential for improving fruity, floral, umami, and aftertaste profiles.