Screening, identification and growth characteristics of dominant yeasts in Tongxian fish

As a local flavor specialty dish of Xinyang Shangcheng, Tongxian fish is favored by consumers for its unique flavor. Yeast is a key factor affecting the flavor quality of fermented foods. Therefore, Tongxian fishes fermented for 5 d, 10 d, and 15 d were selected as the isolation sources and the yeasts were isolated and purified. The fermentation performance, protein decomposition ability, and ester production ability of isolated strains were investigated to screen excellent yeast. The strains were identified based on morphological observation, physiological and biochemical tests (sugar fermentation test, assimilation test) and 26S rDNA gene sequence, and their growth characteristics and optimal culture conditions were analyzed. The results showed that 19 yeast strains were isolated from the samples, and excellent yeast strain C14 was rescreened. After identification, the strain C14 was Yarrowia lipolytica. The strain C14 grew actively at 8-24 h, and the optimal cultivation conditions were as follows: temperature 28-36 ℃, salt concentration less than 5%, pH 5, and rotation speed 200 r/min. The study results could provide theoretical basis for preparation and standardized production of Tongxian fish.