Microbial Diversity in Olive Mill Wastewater: Insights, Implications, and Future Directions

When olives are processed into olive oil, olive mill wastewater (OMW) is produced, containing water, olive pulp, skin, and other organic materials. Rich in polyphenols and lipids, this complex waste can pollute soil and water sources due to its high organic and toxic compound content, acidity, salinity levels, and unbalanced nutrients. In this study, we focused on revealing the microbial diversity and physicochemical properties of OMW and discussed biotechnological potential. In this study, some physicochemical parameters of the OMW samples obtained from five different olive oil production enterprises in Çanakkale province and microbial diversity were determined by metabarcoding method using V3/V4 regions of 16S rRNA. It was observed that all OMW samples were classified as much polluted water in terms of temperature, pH, dissolved oxygen, biochemical oxygen demand, total nitrogen, total organic carbon, and oil and grease values. It was determined that the rates of oleuropein, an important phenolic component, varied between 7.1 mg/L—117 ± 7 mg/L, and the highest rate was obtained from station IV. When the biodiversity data of all stations were compared, it was revealed that the first five families represented by the highest number of genera and species were Enterobacteriaceae (Gammaproteobacteria), Lactobacillaceae (Firmicutes), Acetobacteraceae (Alphaproteobacteria), Erythrobacteraceae (Alphaproteobacteria) and Prevotellaceae (Bacteroidetes). While the obtained physicochemical parameters reveal the disadvantages of releasing OMW samples into the environment without treatment, the high microbial diversity percentages in all OMW samples show that OMW is an important source for comprehensive microbial biotechnology studies.