Abstract:

Acetoin (ACT) is the precursor of tetramethylpyrazine, a popular food flavor found in different traditional
fermented foods. In our present study, we isolated approximately 200 pure cultures by forming transparent zone on GYC
agar medium, and obtained 28 ACT-producing strains from these isolates by Voges-Proskauer (V-P) colorimetric assay and
gas chromatograph with flame ionization detector (GC-FID). Based on ACT level, C92 strain with the highest yield was
selected for further analysis. It was identified as Acetobacter pasteurianus by physiological and biochemical characteristics
and 16S rRNA gene sequence similarity. We examined ACT level of C92 strain under different conditions and found that the
optimal culture conditions that provided maximum ACT yield of 19.04 g/L were 31.31 ℃, pH 6.55, shaking at 209 r/min,
48 h and inoculum size of 8.27%, representing a 35.8% increase compared to that before optimization. Therefore, C92 has a
promising potential in the production of vinegar.

Key words: Liangzhou fumigated vinegar, Acetobacter pasteurianus, acetoin, response surface optimization