Growth and Rhamnolipid Production Performance of Pseudomonas aeruginosa on Crude Biomass Carbohydrates and Bioenhancer-Based Growth Media

Novel growth media formulations for improved rhamnolipid production from Pseudomonas aeruginosa PAO1 were evaluated on four carbohydrate sources: glucose, glycerol, soy hull hydrolysate (SHH), and mimicking soy hull hydrolysate (MSH) along with bioenhancers and other media components. This study is aimed at understanding the effect of different types of human neuroendocrine bioenhancers on growth performance and rhamnolipid titer generation of the Pseudomonas aeruginosa PAO1 in a growth media containing sustainable crude biomass carbohydrates. Optimization of the media factors for improved rhamnolipid titers with Pseudomonas aeruginosa PAO1 was performed through a high-throughput response surface study for the best growth rate for concentrations of carbohydrates; bioenhancers, norepinephrine (NE) and dopamine (DP); and iron (Fe). In the high-throughput study, the microbial growth rates for all sugar types ranged between 0.2 and 0.5 log numbers in OD (optical density, indicating the concentration of bacterial cells within a liquid culture, as determined by a spectrophotometer) h−1 at 600 nm, with glucose providing the highest growth rate in the best response surface media combination at 2.5% glucose concentration, 160 µM norepinephrine, 66 µM dopamine, 0.03% Fe concentration. The effect of this media on growth and rhamnolipid production was further verified in 100 mL shake flasks. The highest OD and rhamnolipid titers were achieved for glucose- and glycerol-based media at 2.78 g/L and 2.72 g/L, respectively, whereas significantly lower titers at 1.98 g/L and 1.72 g/L were observed for SHH- and MSH-based media, respectively. No significant growth enhancement effects by the bioenhancers norepinephrine and dopamine were observed at the concentrations evaluated.