According to Ribera et al. [48], who examined the strain P. putida KT2442, it was observed that the particular microorganism was able to accumulate 1.52% g PHAs/g CDM while the rate of PHAs biosynthesis was qPHAs= 0.56 mg L−1h−1. This study is the only one dealing with the production of PHAs by bacteria of the Pseudomonas genus from olive mill wastewater (alpechin). On the other hand,when the same strain was grown in oleic acid PHAs accumulation reached 23% g PHAs/g CDM [49].
It has been reported that in the case of recombinant P. putida KT2442 PHAs content reached up to 65% g PHAs/g CDM when sodium octanoate was provided as carbon source but PHAs content dropped to ∼3.5% g PHAs/g CDM when olive mill wastewater was used [50]. The results of the present study are similar to those of Ribera et al. [48] although different strains of the Pseudomonas genus were examined. Low PHAs production efficiency in the case of acidified OMW could be attributed to the complexity of the wastewater or to inhibitory effect of ‘toxic’ compounds present in OMW, such as polyphenols.
The complex nature of OMW which was used as carbon source caused differences on the production process parameters com-pared to the synthetic medium. However, this is not in agreement with the findings of Dionisi et al. [6]. When acidified OMW was fedagainst synthetic medium to an enriched mixed culture, no difference in the PHAs yield coefficient (0.54 g PHAs/g VSS) was observed.Moreover, the authors concluded that the culture, apart from the VFAs, consumed other carbon substrates, such as alcohols.