In vivo evolution and identification of predominant bacterial communities in naturally fermented Greek Chalkidiki table olives: Expression of bacterial genes involved in metabolic pathways

Abstract

Greek-style table olives involve debittering process by a spontaneous fermentation without any additional treatments which is why it is considered to be a good source of bio-active components and promote distinct organoleptic properties. The current study aims to invenstigate crucial factors that affect fermentation process of Chondrolia cultivar (Chalkidiki) greek-style fermented table olives. Application of advanced identification techniques has been respectively applied to primarily undermine bacteria behavior and dynamics throughout different stages of fermentation and provide in vivo expression analysis by identification of several bacterial genes activity and their expression at different stages of fermentations that indicate regulation/ degradation of certain phenolic compounds. Evolution and identification of predominant LAB has been presented where I.parafarraginis is found to be most predominant sp at end-point of fermentation whereas mid-stages prevalence of L.algidus has been examined. Moreover, most commonly observed gram-negatives during all stages of fermentation being Salinibacter ruber, Pseudomonas spp (Pseudomonas savastinoi, Pseudomona deceptionensis, Pseudomonas orientalis) and Pelomonas Puraquae have been observed. Out of 4 tested primers GLUC FI GLUC_RI (B-Glucosidase gene), GDC_FI GDC_R1 (Gallate decarboxylase gene) PCUD FI PCUD R1 (p-Coumaric decarboxylase gene) TAN_FI TAN_R1 (Tannase gene) gene expression has been observed at early stages for p-Coumaric decarboxylase and late stages for Gallate decarboxylase. Total phenolic content has been examined via Folin Ciocalteu assay showing on statistically significant changes of phenolic contents obtained throughout their release in the brine and a 55% antioxidant activity has been presented via DPPH assay which demonstrated that olives have kept initial antioxidant potency as opposed to 65% of initial inihibition of the samples.