Combinational system for biodegradation of olive oil mill wastewater phenolics and high yield of bio-hydrogen production.

Olive oil mill wastewater (OMW) is a significant pollutant in the Mediterranean region. In the present contribution, we showed clearly that microorganisms (microalgae and OMW-microflora) activated the biodegradation of OMW-phenolics and produced a high yield of hydrogen (H2). In a closed incubation system, the appropriate adjustment of OMW-pH leads to the establishment of anoxic conditions through the oxygen consumption of microorganisms during the first incubation day. The biodegradation procedure of OMW-phenolics needs oxygen. Therefore, after the establishment of anoxic conditions, the biodegradation stopped and the activation of hydrogenases started, leading to a continuous high yield of bio-hydrogen production. If the cultivation system re-opened (oxygen enrichment), the OMW-phenolic biodegradation (oxygen dependent process) started again and therefore the detoxified OMW could be used for further biotechnological applications (production of biodiesel, bioalcohols, organic fertilizers, etc.). Apart from the environmental compatibility of the method and the sustainability of such a combinational application (OMW detoxification and high yield of hydrogen production) in the context of a green biotechnology approach, the cost/profit ratio appears to be particularly tempting and guarantees its widespread use in the near future. The present contribution proposes a solution to a major environmental problem by upgrading its solution to a high-value product.