Production of polyhydroxyalkanoates from dephenolised and fermented olive mill wastewaters by employing a pure culture of Cupriavidus necator

The feasibility of producing polyhydroxyalkanoates (PHAs) by feeding a pure culture of Cupriavidus necator with a pre-treated olive mill wastewater (OMW) was demonstrated at 500mL shaken flask scale. The OMW was previously dephenolised and then fermented to produce an effluent rich in volatile fatty acids (VFAs). The latter stream (OMWAcid) was then employed as the carbon source for PHAs production.Firstly, pre-grown cells were fed with different dilutions of OMWAcid, namely: 25, 50, 75 and 100% (v/v). Significant inhibitory effects were observed when OMWAcid concentration was 75 and 100%. Thereafter, experiments with laboratory prepared solutions, simulating the OMWAcid, allowed to demonstrate that polyphenols significantly contributed to the observed inhibition. Furthermore, The copolymer poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (poly(HB-co-HV)), containing 11% of hydroxyvalerate, was accumulated up to 55% of the cells dry weight when two consecutive accumulation batch processes were carried out with 25% of OMWAcid and without adding any exogenous carbon source.The obtained results are promising in the perspective of continuing the production study at a bench-top bioreactor scale and thereafter analysing the possibility of developing a biotechnological PHAs production process as a part of an integrated OMW valorization process.