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

摘要

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, (NH_4)_2PO_4, incubation time, trace metal solution, MgCl_2, K_2HPO_4, KH_2PO_4 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, (NH_4)_2PO_4, K_2HPO_4 and KH_2PO_4 having high t-values were selected to study their optimal relationship for maximal PHA production using 2~4 Central Composite Design. The optimal composition of the medium was found to be at 7.5 gL ~1 oleic acid, 0.4 g L ~1(NH_4)_2PO_4,3.0gL~1K_2HPO_4 and 1.5gL ~1KH_2PO_4 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.