Dual nitrogen–oxygen limitation
The behavior of all cultures was identical with the one observed in the case of synthetic medium when they were facing dual nitrogen–oxygen limitation. When the enriched culture was used PHAs production decreased from 8.8% to 3.2% g PHAs/g CDM where as, strains B, C, D, E and F showed no significant difference on the PHAs accumulation percentages, yields and rates. Strain A seemed to respond positively to the low oxygen concentration accumulating 11.5% versus 6.2% g PHAs/g CDM under conditions of sufficient oxygen supply. In strain A the yield coefficient YPHAs/S significantly increased probably due to the preference of the microorganism to accumulate PHAs against other intracellular macromolecules under those conditions. This behavior is in accordance with the one observed under dual nitrogen–oxygen limitation using synthetic wastewater as substrate.
Despite the fact that strain A showed the higher PHAs content in this case, production of PHAs using the enriched culture seemed beneficial due to shorter batch duration. The enriched culture accumulated 3.2% g PHAs/g CDM, while stain A accumulated almost a three-fold amount, 11.5% g PHAs/g CDM, but in 328 h.
To our knowledge, there is no report to date that deals with the production of PHAs from OMW under simultaneous nitrogen and oxygen limitation.