The influence of nitrogen limitation on mcl-PHA synthesis by two newly isolated strains of Pseudomonas sp.

The nucleotide composition of key enzymes involved in medium-chain-length polyhydroxyalkanoates (mcl-PHA) synthesis was analyzed in two newly isolated strains of Pseudomonas. The isolated strains were tested for their abilities to synthesize polyhydroxyalkanoates using three different substrates as a carbon source: sodium octanoate, oleic acid, and sodium gluconate. Both analyzed strains were able to accumulate mcl-PHA in a range from 2.07 to 21.40%, which depended on the substrate used. Potential nitrogen-dependent regulation of mcl-PHA synthesis was analyzed by cell cultivation in nitrogen-limiting and non-limiting conditions. The analyzed strains demonstrated an incremental increase of mcl-PHAs in response to nitrogen starvation when oleic acid and sodium gluconate were applied as the carbon source. The transcriptional analysis showed that the induction of gene coding for PHA synthases was correlated with an increment in mcl-PHAs content. Both analyzed strains revealed differences in terms of the studied gene's expression, showing a dependence on the carbon source used.