Function and safety evaluation of Staphylococcus epidermidis with high esterase activity isolated from strong flavor Daqu
Pei Xu, Yang Han, Lei Tian, Qingyan Guo, Hang Chen, Xinyue Wei, Ying Liu, Zongjun He, Jiaxu Zhang, Jing Luo, Dong Li, Tongwei Guan
Abstract
This study was aimed at evaluating the safety of Staphylococcus epidermidis YTPW-4 isolated from strong flavor Daqu and its beneficial functional characteristics in Baijiu-making. The content of ethyl caproate catalyzed by crude enzyme solution of Staphylococcus epidermidis YTPW-140 was 583.09 mg/100 mL, and the activity of esterase was 2.13 U/mL. Vancomycin, erythromycin, and gentam were sensitive to the strain, which was negative for the causative gene, hemolytic activity, and biofilm formation capacity. In addition, the strain was selected for laboratory-scale fermentation using HS-SPME-GCMS and statistical analysis to confirm its role in the production of flavor compounds. Propyl-3-methylbutyrate, hexanoic acid, and ethyl acetate had higher contents after fermentation than other flavor compounds, at 530.40 μg/L, 471.07 μg/L, and 297.33 μg/L, respectively. There was also a small amount of ethyl hexanoate in these products. Esterase could increase the levels of short-chain free fatty acids, which were precursors of flavor compounds. Most importantly, the isolate maintained viability under simulated pit conditions, and was resistant to pH 3.5 and 8% ethanol. These results indicated that the strain had the potential to be used as a starter to improve the quality of Nongxiangxing baijiu.