Unusual poly(3-hydroxyalkanoate) (PHA) biosynthesis behavior of Pseudomonas putida Bet001 and Delftia tsuruhatensis Bet002 isolated from palm oil mill effluent

Pseudomonas putida Bet001 and Delftia tsuruhatensis Bet002, isolated from palm oil mill effluent, accumulated poly(3-hydroxyalkanoates) (PHAs) when grown on aliphatic fatty acids, sugars, and glycerol. The substrates were supplied at 20:1 C/N mole ratio. Among C-even n-alkanoic acids, myristic acid gave the highest PHA content 26 and 28 wt% in P. putida and D. tsuruhatensis, respectively. Among C-odd n-alkanoic acids, undecanoic gave the highest PHA content at 40 wt% in P. putida and 46 wt% in D. tsuruhatensis on pentadecanoic acid. Sugar and glycerol gave <10 wt% of PHA content for both bacteria. Interestingly, D. tsuruhatensis accumulated both short- and medium-chain length PHA when supplied with n-alkanoic acids ranging from octanoic to lauric, sucrose, and glycerol with 3-hydroxybutyrate as the major monomer unit. In P. putida, the major hydroxyalkanoates unit was 3-hydroxyoctanoate and 3-hydroxydecanoate when grown on C-even acids. Conversely, 3-hydroxyheptanoate, 3-hydrxoynonanoate, and 3-hydroxyundecanoate were accumulated with C-odd acids. Weight-averaged molecular weight (M_w ) was in the range of 53-81 kDa and 107-415 kDa for P. putida and D. tsuruhatensis, respectively. Calorimetric analyses indicated that both bacteria synthesized semicrystalline polymer with good thermal stability with degradation temperature (T_d ) ranging from 178 to 282 °C.