ENHANCING SOLUBILIZATION OF SPARINGLY SOLUBLE ORGANIC-COMPOUNDS BY BIOSURFACTANTS PRODUCED BY NOCARDIA-ERYTHROPOLIS

The goal of this research was to produce nontoxic, biodegradable surfa ctants from Nocardia erythropolis (American Type Culture Collection [A TCC] 4277) and to investigate their potential for enhancing the solubi lity of sparingly soluble organic compounds (SSOCs). After biosurfacta nts were harvested from the culture broth, SSOC removal capabilities f rom aqueous systems by micelles and monomers were determined. Nocardia erythropolis was grown in a 500-mL batch reactor with n-hexadecane as the sole carbon source. Surface tension of the mineral salts medium d ropped from 64 dyne/cm to 41 dyne/cm within 24 hours after inoculation with an acclimated culture of N. erythropolis, indicating the product ion of appreciable quantities of surface-active agents. The lowest sur face tension value of 35.2 dyne/cm was reached in 4 days. Maximum prod uction of surfactant was also observed at 4 days. Sparingly soluble or ganic compounds were partitioned into surfactant micelles that form wh en the surfactant concentration exceeds the critical micelle concentra tion. Sparingly soluble organic compound partitioning into micelles in creased with decreasing SSOC solubility. The partition constants by mi celles were 0.002 0, 0.008 6, and 0.041 2 L/mg for toluene, p-xylene, and trimethylbenzene, respectively. The partitioning capacity of p-xyl ene by the biosurfactants produced from N. erythropolis was an order o f magnitude greater than that by the synthetic surfactant sodium dodec ylsulfate (SDS).