Evaluation of date seed oil and date molasses as novel carbon sources for the production of poly(3Hydroxybutyrate-co-3Hydroxyhexanoate) by Cupriavidus necator H16 Re 2058/pCB113

Cupriavidus necator H16 Re2058/pCB113 could effectively utilize oil sources to synthesize P(3HB-co-3HHx). In this study, P(3HB-co-3HHx) biosynthesis procedure with optimally controlled (between 2–28) 3HHx mol% was established for C. necator H16 Re2058/pCB113 by regulating the amounts of dual carbon sources supplied; date molasses and date seed oil. Alone, date molasses supplied at 20 g/L total sugar equivalents to recombinant C. necator resulted in pure P(3HB) biosynthesis, with accumulation up to 28 wt% of cell dry weight (CDW), and effective total biomass of 4 g/L. Whereas, date seed oil supply alone or in combination with date molasses resulted in P(3HB-co-3HHx) biosynthesis. P(3HB-co-3HHx) with as high as 28 mol% 3HHx, up to 80 wt% of CDW and total biomass of 7.6 g/L were produced using 10 g/L date seed oil as the sole carbon source. The results of PHA production in the presence of date seed oil as a sole carbon source was obtained with a modest yield at a range of 0.38–0.62 g-PHA per g-date oil used. Gel permeation chromatography (GPC) analyses of these P(3HB-co-3HHx) copolymers exhibited weight average molecular weights (Mw) between 500 − 690 kDa. Differential scanning calorimetry (DSC) analyses showed Tm values of 157 °C and 85 °C for P(3HB) and P(3HB-co-28 mol% 3HHx), respectively. NMR analyses (1H and 13C) of P(3HB-co-3HHx) copolymers confirmed the incorporation of 3HHx monomers between 2–28 mol% depending on the supplied dual carbon source composition.