Bioreactor scale co-production of poly(hydroxyalkanoate) and rhamnolipids with distinct nitrogen sources

The present study focuses on the efficient and optimized co-production of poly(hydroxyalkanoate) (PHA) and rhamnolipids (Rhls) in a batch bioreactor using Pseudomonas aeruginosa mutant strain cultivated on soybean oil in the minimal media provided with three sole nitrogen sources of sodium nitrate, carbamide, and ammonium chloride at different agitation speeds and dissolved oxygen (DO) saturation (%). Herein, up to 3.81 g PHA L −1 and 1.63 g Rhls L −1 could be produced at 200 rpm and 40% DO saturation, which then improved to 3.95 and 2.04 g L −1 , respectively, at 250 rpm and 50% DO saturation, both with carbamide as a sole nitrogen source. The Rhls hence produced were quantified using a modified methylene blue assay whereas the biopolymer was elucidated using the Fourier transform infrared spectroscopy, liquid chromatography-mass spectrometry, and differential scanning calorimetry. The results demonstrated that the PHA hence produced was a poly(3-hydroxybutyrate) of the molecular mass 448.5 amu. Highlights Herein, simultaneous poly(hydroxyalkanoate) (PHA) and rhamnolipids (Rhls) production is done on a bioreactor scale. The effect of different nitrogen sources on PHA and Rhls yields was investigated under various fermentation conditions. Chemical analysis elucidated that produced polymer is poly(3-hydroxybutyrate) (PHB). The production process has been evaluated using fermentative kinetics. There is a need to further economize the PHB/Rhls production and recovery processes, and to explore their feasible applications.