**5. Conclusion**

The olive oil industry generates large amounts of olive mill wastes (OMWs) as by-products that are harmful to the environment. About 30 million tons of OMWs per year are produced in the world. Thus, more research is needed on the development of new bioremediation technologies and strategies of OMWs, as well as the valorisation by microbial biotechnology. The fermentation of fatty low-value renewable carbon sources like OMWs aiming at the production of various added-value metabolites is a noticeable interest in the sector of industrial microbiology and microbial biotechnology.

Microbiological studies show that presence of yeasts, but not of bacteria and moulds in the olive oil. Some of the yeasts are considered useful as they improve the organoleptic characteristics of the oil during preservation, whereas others are considered harmful as they can damage the quality of the oil through the hydrolysis of the triglycerides. Olive oil and its by-products could provide a source of low-cost fermentation substrate and isolation of new microorganisms with biotechnological potentials.

OMWs treatment processes that employ physical, chemical, biological and combined technologies have been tested. Among the different options, biological treatments or bioremediation are considered the most environmentally compatible and the least expensive. Bioremediation occurs either under aerobic or anaerobic conditions. Aerobic processes are applied waste streams of OMWs with low organic loads, whereas anaerobic processes are applied waste streams with high organic loads.

Microbial biotechnology strategies and methods in olive oil industry were used to reduce chemical oxygen demand (COD), biological oxygen demand (BOD) and phenolic compounds of OMWs with a concomitant production of biotechnologically valuable products such as enzymes (lipases, β-glucosidase, phytase, tannase, lignin peroxidase, manganese peroxidise, laccase and pectinases), organic acids (citric, isocitric and oxalic acids), biopolymers and biodegradable plastics (xanthan, β-glucan and polyhydroxyalkanoates), biosurfactants, food

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**Part 3** 

**Bioavailability and Biological** 

**Properties of Olive Oil Constituents** 

