Starter Culture Selection for Making Chinese Sesame-Flavored Liquor Based on Microbial Metabolic Activity in Mixed-Culture Fermentation

Abstract

Selection of a starter culture with excellent viability and metabolic activity is important for inoculated fermentation of traditional food. To obtain a suitable starter culture for making Chinese sesame-flavored liquor, the yeast and bacterium community structures were investigated during spontaneous and solid-state fermentations of this type of liquor. Five dominant species in spontaneous fermentation were identified: Saccharomyces cerevisiae, Pichia membranaefaciens, Issatchenkia orientalis, Bacillus licheniformis, and Bacillus amyloliquefaciens. The metabolic activity of each species in mixed and inoculated fermentations of liquor was investigated in 14 different cocultures that used different combinations of these species. The relationships between the microbial species and volatile metabolites were analyzed by partial least-squares (PLS) regression analysis. We found that S. cerevisiae was positively correlated to nonanal, and B. licheniformis was positively associated with 2,3-butanediol, isobutyric acid, guaiacol, and 4-vinyl guaiacol, while I. orientalis was positively correlated to butyric acid, isovaleric acid, hexanoic acid, and 2,3-butanediol. These three species are excellent flavor producers for Chinese liquor. Although P. membranaefaciens and B. amyloliquefaciens were not efficient flavor producers, the addition of them alleviated competition among the other three species and altered their growth rates and flavor production. As a result, the coculture of all five dominant species produced the largest amount of flavor compounds. The result indicates that flavor producers and microbial interaction regulators are important for inoculated fermentation of Chinese sesame-flavored liquor.

Bacterial communities and volatile compounds in Doubanjiang, a Chinese traditional red pepper paste

“…Nonanal, exhibiting a soapy flavour, might be associated with the metabolism of Bacillus licheniformis (Wu et al . ). These aldehyde compounds, mainly associate with sweet, fruity odours, played an important role as enhancing flavour quality (Lee and Ahn ).…”

Flavor Profile of Chinese Liquor Is Altered by Interactions of Intrinsic and Extrinsic Microbes

“…The fermentation medium was prepared with sorghum as previously reported (16). The original total reducing sugar in the extract was about 45.5 g/kg.…”

“…This medium was sealed in 2-liter beakers and autoclaved at 121°C for 15 min. Yeast cultures were inoculated by sterile loops in 250-ml Erlenmeyer flasks with 50 ml sorghum extract, which was prepared as previously reported (16). Fermentations were conducted at 150 rpm and 30°C for 48 h. Yeast cell numbers were determined using a hemocytometer (16).…”

“…Yeast cultures were inoculated by sterile loops in 250-ml Erlenmeyer flasks with 50 ml sorghum extract, which was prepared as previously reported (16). Fermentations were conducted at 150 rpm and 30°C for 48 h. Yeast cell numbers were determined using a hemocytometer (16). These strains were then inoculated into solid-state sorghum in beakers for mixed fermentation, with the initial cell density of each strain adjusted to 1 ϫ 10 5 CFU/g.…”

“…Yeast enumeration was carried out on Wallerstein Laboratory nutrient (WLN) medium (17), in which the five strains showed different macroscopic features, which were detailed in a previous report (15). According to the macroscopic features (texture, surface, margin, elevation, and color), colonies of different types on the WLN medium were counted separately (15,16). Standard deviations were calculated from triplicate repetitions of the fermentation.…”