Extraction of biosurfactants from LDPE and PAH degrading bacterial strains isolated from plastics and oil contaminated sites: Statistical optimization using response surface methodology

Abstract

Bacterial strains degrading hydrophobic pollutants are known to produce surfactants, which reduce the hydrophobicity and enhance the biodegradation process. The bacterial strains reported in previous study with the ability to degrade LDPE and PAH were used in this study to screen for their ability to produce biosurfactants. The produced biosurfactant was optimized for enhanced activity using Response Surface Methodology (RSM). The P < 0.05 confirmed the reliability of the generated quadratic model for biosurfactant activity. The biosurfactant produced by S. hominis and V. owensi showed a positive hemolytic activity with a constant increase in the diameter of the zone formed. The former resulted in 4 µg/mL and the latter in 3 µg/mL of CMC. FTIR analysis indicated the presence of C-H stretching, C=O stretching, N-H stretching, and C=C stretching as common in biosurfactants produced by both bacterial strains. The ¹H NMR revealed the presence of secondary amides/imides in the biosurfactants. GC–MS analysis indicated the presence of esters and acids in the biosurfactant. These conclude that the extracted biosurfactant is a mixture of compounds which degrades LDPE and PAHs.