Single batch co-production of Pseudomonad polyhydroxybutyrate and rhamnolipids on wasted cooking oil under salinity stress

Abstract Polyhydroxyalkanoates (PHAs) are emerging biodegradable bioplastics, and rhamnolipids are sustainable biosurfactants; both are considered as alternatives to synthetic petroleum-based plastics and surfactants, respectively. Herein, the effects of three distinct nitrogen sources on PHAs and rhamnolipid yields during the fermentation process have been undertaken. The study focuses on the optimum co-production of PHAs and rhamnolipid using a Pseudomonas aeruginosa strain grown on wasted soybean oil (WSO) with different nitrogen sources in the minimal salts’ media under salinity stress with shake flask conditions. The yields of PHAs and rhamnolipids were observed to be 2.20 g L−1 and 1.02 g L−1, respectively, with carbamide as the sole nitrogen and WSO (2 %, w/v) as the sole carbon source. The fermentative yields of both PHAs (2.37 g L−1) and rhamnolipids (1.24 g L−1) roughly increased up to 8 % under salinity stress. The products were characterized using advanced analytical techniques. The chemical structure of rhamnolipid with this strain had previously been elucidated, whereas the PHA produced was identified as a poly(hydroxybutyrate).