Production of Polyhydroxyalkanoates From Underutilized Plant Oils by Cupriavidus necator

Utilization of neglected oils for polyhydroxyalkanoates (PHAs) production will provide vast arrays of carbon substrates, lower its production cost, and boost global PHA production. The scope of this study is to evaluate the potential of desert date oil, bitter apple oil, African elemi oil, and Amygdalus pedunculata oil from Africa and some parts of Asia as novel carbon sources for PHA production. The desert date kernels and bitter apple seeds contain up to 45.5 and 53.2% of oil-based on dry weight. Fatty acid methyl ester (FAME) results showed the presence of palmitic (C16:0), stearic (C18:0), oleic (C18:1), and linoleic (C18:2) acids as the major fatty acids constituting 97–99% of the total fatty acids. Both strains of Cupriavidus necator H16 and Re2058/pCB113 utilizes the oils effectively as carbon sources for poly(3-hydroxybutyrate), P(3HB) and poly(3-hydroxybutyrate-co-3-hydroxyhexanoate), P(3HB-co-3HHx) production, respectively. A maximum cell dry weight (CDW) of 8–9 g/L−1 (C. necator H16) and 6–8 g L−1 (Re2058/pCB113) at a C/N ratio between 24 and 36 was achieved from shake flask cultures. The oils are suitable for the biosynthesis of high concentration of P(3HB) (6 g L−1) and P(3HB-co-3HHx) (5 g L−1) with 31 mol% 3HHx. Gel permeation chromatographic (GPC) analysis of the PHAs revealed high PHA molecular weights (Mw) of 510 000–630 000 for copolymer and 1 580 000–2 400 000 Da for homo-polymer. This study shows that the underutilized oils are potential feedstock to produce PHA that can substitute palm oil.