Enhanced rhamnolipid production by Pseudomonas aeruginosa USM-AR2 via fed-batch cultivation based on maximum substrate uptake rate

A fed-batch strategy was established based on the maximum substrate uptake rate (MSUR) of Pseudomonas aeruginosa USM-AR2 grown in diesel to produce rhamnolipid. This strategy matches the substrate feed rates with the substrate demand based on the real-time measurements of dissolved oxygen (DO). The MSUR was estimated by determining the time required for consumption of a known amount of diesel. The MSUR trend paralleled the biomass profile of Ps.aeruginosa USM-AR2, where the MSUR increased throughout the exponential phase indicating active substrate utilization and then decreased when cells entered stationary phase. Rhamnolipid yield on diesel was enhanced from 0 center dot 047 (g/g) in batch to 0 center dot 110 (g/g) in pulse-pause fed-batch and 0 center dot 123 (g/g) in MSUR fed-batch. Rhamnolipid yield on biomass was also improved from 0 center dot 421 (g/g) in batch, 3 center dot 098 (g/g) in pulse-pause fed-batch to 3 center dot 471 (g/g) using MSUR-based strategy. Volumetric productivity increased from 0 center dot 029gl(-1)h(-1) in batch, 0 center dot 054gl(-1)h(-1) in pulse-pause fed-batch to 0 center dot 076gl(-1)h(-1) in MSUR fed-batch. Significance and Impact of the Study This study highlights the significance of an effective fed-batch strategy for rhamnolipid production in a submerged fermentation using a water-immiscible substrate, based on maximum substrate uptake rate. The impact of this strategy ensured that the substrate was supplied at the rate matching the maximum substrate utilization by the cells without excess feeding, leading to increased rhamnolipid production, yield and productivity.