Identification and analysis of the metabolic functions of a high-salt-tolerant halophilic aromatic yeast Candida etchellsii for soy sauce production.

Salt-tolerant yeasts are very important for the flavor formation in soy sauce fermentation production. A halophilic aromatic yeast was isolated on the basis of the molecular biological and metabolic functions from soy sauce. The ITS nucleotide sequence alignment method was used to identify the strain as Candida etchellsii by subjecting the sequence to NCBI-BLAST in comparison with that of the C. etchellsii strain Miso 0208 (a typical high-salt-tolerant halophilic aromatic yeast strain). Organic acids, amino acids and volatile flavor compounds were produced by the yeast strain which were analyzed by HPLC and SPME-GC/MS methods. Tartaric acid (0.979 ± 0.040 g/l), formic acid (0.636 ± 0.030 g/l), lactic acid (2.80 ± 0.10 g/l), α-alkone glutaric acid (0.132 ± 0.015 g/l), citric acid (2.59 ± 0.10 g/l) and succinic acid (3.03 ± 0.20 g/l) were detected at 72 h of fermentation, respectively. Free and acid hydrolyzed amino acids at levels of 3.7355 ± 0.0027 and 11.5604 ± 0.0037 g/l, respectively, 4-ethyl guaiacols as well as other volatile flavor compounds were also detected.