Maximize rhamnolipid production with low foaming and high yield

In this study, we assessed the boundaries set by these constraints after optimization of basic parameters such as dissolved oxygen concentration (DO), pH and carbon sources. DO 10% and pH 5.5-5.7 were found optimal; cell growth and/or rhamnolipid production were slower at lower DO (5%) or pH (5.0) while foaming became hard to control at higher DO (30%) or pH (6.0 and 6.5). Although the Pseudomonas aeruginosa strain used was selected for its high rhamnolipid production from glycerol as substrate, soybean oil was still found to be a better substrate that increased specific rhamnolipid productivity to 25.8mg/g cells-h from the glycerol-supported maximum of 8.9mg/g cells-h. In addition, the foam volume was approximately halved by using soybean oil instead of glycerol as substrate. Analysis by liquid chromatography coupled with mass spectrometry revealed that rhamnolipid compositions from the two carbon sources were also very different, with primarily (82%) monorhamnolipids from soybean oil and more (64%) dirhamnolipids from glycerol. The optimized fermentation produced 42g/l rhamnolipids at a yield of approximately 47% and a volumetric productivity of 220mg/l-h. These values are among the highest reported.

Source: Enzyme and Microbial Technology - October 17, 2017 Category: Biotechnology Source Type: research