Statistical optimization of biosurfactant production using waste biomaterial and biosorption of Pb2+ under concomitant submerged fermentation

Abstract

The present study was conducted to statistically optimize the biosurfactant production yield of Pseudomonas sp. F5 using raw orange peel extract (Central composite design (CCD) design; Surface tension (ST) reduction = 32.41 dyne/cm; biosurfactant yield = ~2.4 g/L). The extracted biosurfactant was characterized as a glycolipid having predominant mono-rhamnolipids than di-rhamnolipids with a critical micelle concentration (CMC) of 40 mg/L. The potential of strain F5 for good biosurfactant yield during Pb2+ stress and the inherent mechanism for simultaneous biosorption of Pb2+ was also investigated. During concomitant submerged fermentation from 100 to 500 mg/L of Pb2+ showed enhancement in adsorption capacity from 99.44 to 267.86 mg/g respectively having 60.33 ± 2.87 of emulsification index (E24%) measured at 100 mg/L Pb2+ corresponding to maximum biosurfactant production during metal stress. The bacterium showed a high Pb2+ MIC (minimum inhibitory concentration) of 2200 mg/L and efficiently biosorbed Pb2+ ions at pH 7 and a dosage of 0.05 g under varying initial metal ion concentration and contact time. The exothermic biosorption (chemisorption) mechanism was found to be fitted well with Langmuir (R2 = 0.9859) and Pseudo second-order kinetic model (R2 = 0.9975; 200 mg/L) having a maximum adsorption capacity of 294.12 mg/g. These findings indicated the excellent potential of biosurfactant producing strain F5 in the removal of Pb2+ ions from aqueous system and management of agrowastes as suitable carbon substrate.