Microbiological and physicochemical changes during fermentation of solid residue of olive mill wastewaters: Exploitation towards the production of an olive paste – type product

Τo exploit the solid residue of olive mill wastewaters (OMWS) towards the production of an olive paste-type product, natural fermentation of OMWS in NaCl (6% w/v) was implemented for 14 days at 20 °C. The microbiological and physicochemical characteristics of OMWS were examined during fermentation. Fermentation of OMWS was shown to be relied on yeasts while absence of enterobacteria, pseudomonads and staphylococci as well as LAB was observed. Molecular identification of yeast included RFLP analysis of the 5.8S-ITS region. For some selected isolates, sequence analysis of the 5.8S-ITS region was performed. The results were compared to sequences held in public databases (NCBI) and data of papers published previously. These techniques allowed to identify the isolates as Saccharomyces cerevisiae (99% homology) and Pichia membranefasciens (100% homology). Beta-glucosidase was the most important biochemical activity observed, mainly responsible for removing the bitter taste. Paste preparations of fermented OMWS did not differ in sensory characteristics than the controls.