Use of Syzygium aromaticum L. Fermented Plant Extract to Enhance Antioxidant Potential: Fermentation Kinetics

Abstract

The concept of our research is related to the use of stems from S. aromaticum L. in the fermentation process in order to obtain new cosmetic raw materials with high antioxidant potential that are safe for human fibroblasts (HDFs) and keratinocytes (HaCaTs). This evaluation involves treating cell lines with different concentrations of fermented extracts to establish a noncytotoxic dose range. The focus was on evaluating antioxidant activity (AA), total polyphenol content (TPC), and lactic acid efficiency (LAe). For this purpose, the most favourable technological parameters of the fermentation process of stems were determined, including the type of microorganisms, initial sugar content, plant raw material content, and fermentation time. In the present study, lactic acid was obtained with maximum efficiency by stem fermentation in the presence of lactic acid bacteria (LAB) and molasses as a source of six-carbon sugars. In addition, fermentation kinetics was investigated, the essence of which was to identify the technological parameters that allow the highest values of the main functions describing the process (AA, TPC LAe). Two kinetic models were used to determine the kinetics of process function changes during fermentation. The most favourable fermentation conditions for maximum antioxidant activity (26.88 mmol Tx/L ± 0.19), total polyphenol content (5.96 mmol GA/L ± 0.19), and lactic acid efficiency (88% ± 1) were: type of microorganism L. rhamnosus MI-0272, initial sugar content 3.20%, plant raw material content 6.40%, and a fermentation time of 9 days. The values of chelating activity (ChA), AA, and TPC in the fermented stems increased more than two-fold compared to the non-fermented extracts. Reducing activity (RA) and LAe increased to 46.22 mmol Fe3+/L ± 0.29 and 88% ± 1, respectively. Of the kinetic models adopted, follow-up reaction equations and first-order equations best described the time-dependent changes taking place. This study shows that the process function values of AA and LAe are dependent on the LAB strain and the content of the plant material, and the rate of change of TPC may largely depend on the forms of phenolic compounds formed during fermentation.