Tyrosol and hydroxytyrosol biodegradation by microalgae

What is it about?

Olive mill wastewater has significant polluting properties, due to high phenolic content (mainly tyrosol and hydroxytyrosol). Growth kinetics and a series of fluorescence induction measurements of Scenedesmus obliquus cultures showed that microalgae can be tolerant to these phenolic compounds. Changes in the cellular energy reserves and the concentration of the phenolic compounds adjust the “toxicity” of these compounds to the microalgae and are, therefore, the main parameters which affect biodegradation. Autotrophic growth conditions of microalgae and high concentrations of tyrosol or hydroxytyrosol induce higher biodegradation compared to mixotrophic conditions and lower phenolic concentrations. When microalgae face simultaneously tyrosol and hydroxytyrosol, biodegradation begins from the hydroxytyrosol, the more energetically demanding compound. All these lead to the conviction that microalgae have a “rational” management of cellular energy balance. Low toxicity levels lead to higher growth and lower biodegradation, while higher toxicity levels lead to lower growth and higher biodegradation. The selection of the appropriate conditions (compatible to the bioenergetic strategies of microalgae) appears to be the key to a successful biodegradation of a series of toxic compounds, paving, thus, the way for future biotechnological applications for solving complicated pollution problems like the detoxification of olive mill wastewater.

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