Zhanyu Shen,Fanghua Mo,Lei Wang,Yu Su,Huijing Han,Kaiyue Zheng,Chunling Wang
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.
To improve the fermentation production of transglutaminase (TGase) from Streptomyces mobaraensis for applications in the food industry, the atmospheric and room-temperature plasma (ARTP) mutagenesis was applied to breed S. mobaraensis mutants with increased TGase production.After eight rounds of iterative ARTP mutagenesis, four genetically stable mutants, Sm5-V1, Sm6-V13, Sm2-V10, and Sm7-V12, were identified, which showed increased TGase production by 27, 24, 24, and 19%, respectively. The best mutant Sm5-V1 exhibited a maximum TGase activity of 5.85 U/mL during flask fermentation. Compared to the wild-type strain, the transcription levels of the zymogen TGase genes in the mutants increased significantly as indicated by quantitative real-time PCR, while the gene nucleotide sequences of the mutants did not change at all. It was shown that the overexpression of TGase zymogen gene in the mutants contributes to the increase in TGase production.ARTP is a potentially efficient tool for microbial mutation breeding to bring some significant changes required for the industrial applications.
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