Fig. 4
Rhamnolipid yield by ZS1 isolate under various growth conditions. a Growth curve analysis of ZS1 cultures with various amounts of glucose supplements. X- and Y-axis indicate time in hour (h) and cell concentration in optical density (left) or cell dry weight (right), respectively. b Change of surfactant activities during cell growth. X- and Y-axis indicate time (h) and oil-spreading zone (cm2/μl, left) or RL7-11 concentration (g/l, right). c Carbon yield or ratio between product RL7-11 and carbon source glucose in ZS1 cultures with various glucose supplements. X- and Y-axis indicate supplement glucose concentration and carbon yield in RLmol/Glumol, respectively. d RL7-11 productivity in ZS1 cultures with various glucose supplements. X- and Y-axis indicate supplemented glucose concentration and RL7-11 productivity in g/l h, respectively. e Quantification of rhamnolipids by oil-spreading assay (OSZ) or orcinol method (Orcinol) in cultures with various glycerol supplement. No significantly differences between the two methods is observed. f Quantification of rhamnolipids by oil-spreading assay (OSZ) or orcinol method (Orcinol) in cultures with various glucose supplement. Significant difference between the two methods is apparent. Asterisk indicates the significant difference between the results by OSZ and Orcinol