Response surface optimization of poly (3-hydroxyalkanoic acid) production using oleic acid as an alternative carbon source by seudomonas aeruginosa

This study aims at optimizing medium-chain-length Polyhydroxyalkanoate (MCL-PHA) production from Pseudomonas aeruginosa 13003 culture using the statistical design techniques of 2-level factorial design and RSM. Two-level factorial design with eight variables viz. oleic acid, (NH₄)²POM₄, incubation time, trace metal solution, MgCl₂, K₂HPO₄, KH₂PO₄ and inoculum was performed to screen for nutrients that were significantly affecting MCL-PHA production. After the values for the less-influential variables were fixed, oleic acid, (NH₄)₂PO₄, K₂HPO₄ and KH₂PO₄ having high t-values were selected to study their optimal relationship for maximal PHA production using 24 Central Composite Design. The optimal composition of the medium was found to be at 7.5 g L_-1 oleic acid, 0.4 g L_-1 (NH₄)₂PO₄, 3.0 g L_-1 K2HPO4 and 1.5 g L-1 KH2PO4 which gave 60% of CDW as MCL-PHA. This optimization resulted in a 1.6 times increase in the PHA content (60% mass fraction in contrast to 36%). On analysis carbon to nitrogen ratio of 19 was found to be optimum for PHA production. This is the first report on the use of CCD to improve MCL-PHA production from P. aeruginosa.