Kinetic Measurements for Pseudomonas aeruginosa MR01 During Biosurfactant Production in Two-phase System and Developing a Double-Exponential Model for Viable Cell Profile

Biosurfactants are microbial substances which influence interfacial tension. The kinetic study was carried out for Pseudomonas aeruginosa MR01 during biosurfactant production in a two-phase liquid-liquid batch fermentation system. The maximum rhamnolipid concentration (P ) and the yield of biosurfactant per max biomass (Y ) in a 5-L bioreactor containing soybean oil medium were found to be approximately 20.9 g.L and P/X 1 3.1 g.g , respectively. Previously reported kinetic models in aqueous systems, three-parameter Gompertz, 1 Luedeking-Piret and Mercier equations, demonstrated adequate goodness-of-fit (r >0.9) to kinetic data recorded 2 for biomass growth, nitrate consumption and rhamnolipid formation during fermentation. A double-exponential equation was developed to model time-course data of viable cells reported as colony-forming units (CFUs). This suggested equation could accurately predict the experimental data with r 0.947 and provide a powerful = expression to plot microbial cell count pattern. Low values of the standard error of estimate (SEE) and chi-square (x ) confirmed the acceptable level for the accuracy of fit. The 95% confidence intervals for kinetic 2 parameters in all nonlinear models indicated a narrow range simulating the precision of estimation. This kinetic study may work efficiently in the design and scaling-up of the coming aqueous-organic batch bioreactors which are to be applied to the production of biosurfactants.