Affiliation
a Kemerovo State University, Kemerovo, Russian Federation
b Кемеровский государственный университет, Кемерово
c Северо-восточный сельскохозяйственный университет, Харбин
d Харбинский университет коммерции, Харбин
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Abstract
Yeast cultures with advanced metabolic indicators improve various industrial biotechnological processes. New sources of biostimulators involve mainly natural resources, e.g., Taraxacum officinale Wigg. or Trifolium pratense L., as well as non-destructive extraction methods, e.g., supercritical fluid extraction (SCFE). This research featured the effect of CO2 extracts of T. officinale and T. pratense on the enzymatic and physiological profiles of yeast culture.
The experiment involved CO2 extracts of T. officinale and T. pratense obtained by SCFE at 8.0–20.0 MPa and 40°C, as well as industrial brewer’s yeast. The method of gas chromatography made it possible to reveal the chemical composition of the extracts while the Warburg method revealed the fermentation activity of the yeast.
The rational parameters of SCFE for T. officinale included a working pressure of 15.0 MPa while for T. pratense it was 8.0–15.0 MPa. The separate fractions of CO2 extracts obtained with SCFE differed in many aspects. The appearance varied from liquid to waxy. The refractive index correlated with the working pressure. The chemical composition was represented by different mixes of hydrocarbons, phenolic compounds, fatty acids, ketones, aldehydes, and alcohols. The bioactive potential demonstrated antibacterial, antioxidant, and other properties. The analysis involved the chemical composition of the CO2 extracts during longterm storage based on spectrograms and chemical composition. It showed a decrease in the concentration and transformation of polyphenols, flavonoids, and other essential oil components. The microbiological profile of the CO2 extracts was as follows: on storage day 30 at 20–24°C, they contained gram-negative bacteria. However, no microflora was detected when the storage conditions were 2–4°C in the dark. The initial extracts were also microflora-free. When treated with aqueous solutions of CO2 extracts of T. officinale and T. pratense for 20–30 min in an amount of 0.2–2.0% biomass volume, the yeast increased their fermentation activity by an average of 220% while the dead cell count went d own.
In this research, the CO2 extracts of T. officinale and T. pratense demonstrated good prospects as industrial yeast biostimulators.
Keywords
Supercritical CO2 extraction,
chemical composition,
biostimulators,
Taraxacum officinale,
Trifolium pratense,
Saccharomyces cerevisiae,
fermentation activity,
physiological parameters
