Abstract: A yeast strain named A10-2 producing 4-ethylguaiacol was isolated from soy sauce mash. This strain was identified as Wickerhamiella versatilis by morphological observation, physiological and biochemical test, 18S rDNA ITS sequencing and homology sequence analysis. W. versatilis A10-2 was able to tolerate 18% NaCl and grow normally in soy sauce mash while synthesizing 4-ethylguaiacol. Using ferulic acid as the substrate, A10-2 produced the intermediate product 4-vinylguaiacol through decarboxylation by ferulic acid-decarboxylase, which was subsequently derived into 4-ethylguaiacol by 4-vinylguaiacol reductase. Strain A10-2 was capable of producing 4-ethylguaiacol (0.63 mg/mL) from the soy sauce background precursor, which was increased by 19.1 times with addition of 50 mg/L ferulic acid when compared with the control group. Meanwhile, it was found that the mellow aroma and sauce flavor was enhanced, and the saltiness was mitigated. This study highlights the promising potential of W. versatilis A10-2 for flavor improvement of fermented condiments such as soy sauce and sauce paste.

Key words: Wickerhamiella versatilis A10-2; 4-ethylguaiacol; soy sauce; identification; application