Isolation and characterization of Pseudomonas aeruginosa sp. degrading SDS.Department of Biochemistry, Faculty of Biotechnology and Biomolecular Sciences, UniversityPutra Malaysia 43400 UPM Serdang, Selangor, MalaysiaAbstract: Surfactants are synthetic organic chemicals formulated to have cleaning or solubilizing properties. With the development of industrial economy and increasing population density, surfactants have become one of the most widely distributed xenobiotics in the aquatic environment, creating a serious environmental problem. Their toxicities for organisms have already been demonstrated. The primary objective of this study was to isolate and characterize local bacteria that can degrade sodium dodecyl sulfate (SDS), a widely used anionic surfactant. Screening was carried out by conventional enrichment culture technique and the isolate was tentatively identified as Pseudomonas aeruginosa sp. using BiologTM GN plates and partial 16S rDNA phylogeny. The optimal conditions for growth in minimal medium and degradation of SDS by Pseudomonas aeruginosa sp. were at 30°C and pH 6.5 using a phosphate buffer system. Sodium nitrate; at 8.0 gL-1 was found to be the best nitrogen source. The isolated strain exhibited optimal growth at an SDS concentration of 1 gL-1 but can tolerate up to 14 gL-1 SDS, indicating that this isolate was able to survive in a relatively high SDS concentration. 100% of 1.0 gL-1 SDS was completely degraded after 5 and 2 days of incubation before and after optimization respectively. Keywords: SDS, biodegradation, MBAS test, Pseudomonas aeruginosa sp.1.0 INTRODUCTIONAnionic surfactants are groups of xenobiotic compounds that contain sulfonates or e...... middle of paper ......the carbon source of this isolate was studied using the before and after optimization conditions as shown in Figures 10(a) and 10(b) respectively. Complete degradation of 1 g/L SDS before optimization took almost 5 days compared to degradation under optimized conditions where degradation was complete after 2 days of incubation using minimal medium. The SDS content remains unchanged in the non-inoculated control (abiotic control), showing that there is no elimination of SDS. The degradation of SDS at 3 g/L using the consortium of Acinetobacter calcoaceticus and Pantoea agglomerans studied by Abboud et al. (2007) was completed after 5 days of incubation in NB medium supplemented with SDS. However, in their work, only 10% of 3 g/L was successfully degraded after 6 days in minimal medium due to limited supplementation compared to NB medium (Abboud et al., 2007).(a)